Search

Purpose: To survey elite athletes and practitioners to identify (1) knowledge and application of heat acclimation/acclimatization (HA) interventions, (2) barriers to HA application, and (3) nutritional practices supporting HA. Methods: Elite athletes (n = 55) and practitioners (n = 99) completed an online survey. Mann–Whitney U tests (effect size [ES; r]) assessed differences between ROLE (athletes vs practitioners) and CLIMATE (hot vs temperate). Logistic regression and Pearson chi-square (ES Phi [ϕ]) assessed relationships. Results: Practitioners were more likely to report measuring athletes’ core temperature (training: practitioners 40% [athletes 15%]; P = .001, odds ratio = 4.0, 95% CI, 2%–9%; competition: practitioners 25% [athletes 9%]; P = .020, odds ratio = 3.4, 95% CI, 1%–10%). Practitioners (55% [15% athletes]) were more likely to perceive rectal as the gold standard core temperature measurement site (P = .013, ϕ = .49, medium ES). Temperate (57% [22% hot]) CLIMATE dwellers ranked active HA effectiveness higher (P r = .30, medium ES). Practitioners commonly identified athletes’ preference (48%), accessibility, and cost (both 47%) as barriers to HA. Increasing carbohydrate intake when training in the heat was more likely recommended by practitioners (49%) than adopted by athletes (26%; P = .006, 95% CI, 0.1%–1%). Practitioners (56% [28% athletes]) were more likely to plan athletes’ daily fluid strategies, adopting a preplanned approach (P = .001; 95% CI, 0.1%–1%). Conclusions: Practitioners, and to a greater extent athletes, lacked self-reported key HA knowledge (eg, core temperature assessment/monitoring methods) yet demonstrated comparatively more appropriate nutritional practices (eg, hydration).

This systematic review analyzed whether carbohydrate source (food vs. supplement) influenced performance and gastrointestinal (GI) symptoms during endurance exercise. Medline, SPORTDiscus, and citations were searched from inception to July 2021. Inclusion criteria were healthy, active males and females aged >18 years, investigating endurance performance, and GI symptoms after ingestion of carbohydrate from a food or supplement, n = 1) or cycling (n = 13) performance/capacity between food and supplemental sources. Greater GI symptoms were reported with food compared with supplemental sources. Highly heterogenous study designs for carbohydrate dose and timing, as well as exercise protocol and duration, make it difficult to compare findings between studies. A further limitation results from only one study assessing running performance. Food choices of carbohydrate consumed immediately before and during endurance exercise result in similar exercise performance/capacity responses to supplemental carbohydrate sources, but may slightly increase GI symptoms in some athletes, particularly with exercise >2 hr.

Acute morning fasted exercise may create a greater negative 24-hr energy balance than the same exercise performed after a meal, but research exploring fasted evening exercise is limited. This study assessed the effects of 7-hr fasting before evening exercise on energy intake, metabolism, and performance. Sixteen healthy males and females (n = 8 each) completed two randomized, counterbalanced trials. Participants consumed a standardized breakfast (08:30) and lunch (11:30). Two hours before exercise (16:30), participants consumed a meal (543 ± 86 kcal; FED) or remained fasted (FAST). Exercise involved 30-min cycling (∼60% VO2peak) and a 15-min performance test (∼85% VO2peak; 18:30). Ad libitum energy intake was assessed 15 min postexercise. Subjective appetite was measured throughout. Energy intake was 99 ± 162 kcal greater postexercise (p p p p ≥ .458). Fat oxidation was greater (+3.25 ± 1.99 g), and carbohydrate oxidation was lower (−9.16 ± 5.80 g) during exercise in FAST (p p p

Purpose We previously observed increased energy intake (EI) at the meal before planned afternoon exercise, but the proximity of the meal to exercise might have reduced the scale of the pre-exercise anticipatory eating. Therefore, this study examined EI in the 24 h before fasted morning exercise. Methods Fourteen males, experienced with gym-based aerobic exercise (age 25 ± 5 years, BMI 23.8 ± 2.5 kg/m2), completed counterbalanced exercise (EX) and resting (REST) trials. On day 1, subjects were told the following morning’s activity (EX/REST), before eating ad-libitum laboratory-based breakfast and lunch meals and a home-based afternoon/evening food pack. The following morning, subjects completed 30-min cycling and 30-min running (EX; 3274 ± 278 kJ) or 60-min supine rest (REST; 311 ± 34 kJ) fasted. Appetite was measured periodically, and EI quantified. Results Afternoon/evening EI (EX 7371 ± 2176 kJ; REST 6437 ± 2070 kJ; P = 0.017) and total 24-h EI (EX 14,055 ± 3672 kJ; REST 12,718 ± 3379 kJ; P = 0.011) were greater during EX, with no difference between trials at breakfast (P = 0.761) or lunch (P = 0.071). Relative EI (EI minus energy expended through EX/REST) was lower in EX (EX 10,781 ± 3539 kJ; REST 12,407 ± 3385 kJ; P = 0.004). Conclusion This study suggests planned fasted aerobic exercise increases EI during the preceding afternoon/evening, precipitating a ~ 10% increase in EI in the preceding 24-h. However, this increase did not fully compensate for energy expended during exercise; meaning exercise induced an acute negative energy balance.

This study tested the hypothesis that exposure to chlorine-sterilised pool water would impair oral nitrate reduction (ONR). ONR was assessed in elite swimmers before and after morning and afternoon pool-based training. Nonswimmers were only assessed in the morning. ONR was similar in swimmers and nonswimmers (P = 1.000) and unchanged before and after morning and afternoon training (P ≥ 0.341). Therefore, exposure to chlorinated pool water does not interfere with ONR. Novelty Exposure to chlorine-sterilised pool water does not impair oral nitrate reduction in elite swimmers.

Eight well-trained cyclists ingested 68 g·h−1 of a carbohydrate-electrolyte solution with sodium alginate and pectin (CHO-ALG) or a taste and carbohydrate type-matched carbohydrate-electrolyte solution (CHO) during 120 min of cycling at 55% maximal power followed by an ∼20 min time trial. Oxygen uptake, carbon dioxide production, blood glucose concentration, substrate oxidation, gastrointestinal symptoms, and time trial performance (CHO-ALG: 1219 ± 84 s, CHO: 1267 ± 102 s; P = 0.185) were not different between trials. Novelty Inclusion of sodium alginate and pectin in a carbohydrate drink does not influence blood glucose, substrate oxidation, gastrointestinal comfort, or performance in cyclists.

Aims: To examine the independent associations between relative protein intake (g kg−1 day 1) and markers of physical function in those with type 2 diabetes, while also comparing with current guidelines for protein intake. Methods: This analysis reports data from the ongoing Chronotype of Patients with Type 2 Diabetes and Effect on Glycaemic Control (CODEC) study. Functional assessments included: Short Physical Performance Battery (SPPB), 60 s sit-to-stand (STS-60), 4-m gait speed, time to rise from a chair (×5) and handgrip strength. Participants also completed a self-reported 4 day diet diary. Regression analyses assessed whether relative protein intake was associated with markers of physical function. Interaction terms assessed whether the associations were modified by sex, age, HbA1c or body mass index (BMI). Results413 participants were included (mean ± SD:age = 65.0 ± 7.7 years, 33% female, BMI = 30.6 ± 5.1 kg/m2). The average total protein intake was 0.88 ± 0.31 g kg⁻¹ day⁻¹ . 33% of individuals failed to meet the reference nutrient intake for the United Kingdom (≥0.75 g kg⁻¹ day⁻¹ ), and 87% for European recommendations (≥1.2 g kg⁻¹ day⁻¹ ). After adjustment, each 0.5 g/kg of protein intake was associated with an 18.9% (95% CI: 2.3, 35.5) higher SPPB score, 22.7% (1.1, 44.3) more repetitions in STS-60, 21.1% (4.5, 37.7) faster gait speed and 33.2% (16.9, 49.5) lower chair rise time. There were no associations with handgrip strength or any interactions. Conclusions: Relative protein intake was positively associated with physical function outcomes, even after consideration of total energy intake. As a number of individuals were below the current guidelines, protein intake may be a modifiable factor of importance for people with type 2 diabetes. Refereed/Peer-reviewed

The impact of alterations in hydration status on human physiology and performance responses during exercise is one of the oldest research topics in sport and exercise nutrition. This body of work has mainly focussed on the impact of reduced body water stores (i.e. hypohydration) on these outcomes, on the whole demonstrating that hypohydration impairs endurance performance, likely via detrimental effects on a number of physiological functions. However, an important consideration, that has received little attention, is the methods that have traditionally been used to investigate how hypohydration affects exercise outcomes, as those used may confound the results of many studies. There are two main methodological limitations in much of the published literature that perhaps make the results of studies investigating performance outcomes difficult to interpret. First, subjects involved in studies are generally not blinded to the intervention taking place (i.e. they know what their hydration status is), which may introduce expectancy effects. Second, most of the methods used to induce hypohydration are both uncomfortable and unfamiliar to the subjects, meaning that alterations in performance may be caused by this discomfort, rather than hypohydration per se. This review discusses these methodological considerations and provides an overview of the small body of recent work that has attempted to correct some of these methodological issues. On balance, these recent blinded hydration studies suggest hypohydration equivalent to 2–3% body mass decreases endurance cycling performance in the heat, at least when no/little fluid is ingested.

Effects of exercise on subsequent energy intake are well documented, but whether preexercise energy intake is affected by future planned exercise is unknown. This study investigated the effect of planned late-afternoon exercise on appetite and energy intake before (breakfast and lunch) and after (evening meal/snacks) exercise.Twenty healthy, active participants (10 male; age, 23 ± 5 yr; body mass index 23.7 ± 3.2 kg·m; V˙O2peak, 44.1 ± 5.4 mL·kg··min) completed randomized, counterbalanced exercise (EX) and resting (REST) trials. After trial notification, participants were provided ad libitum breakfast (0800 h) and lunch (1200 h) in the laboratory, before completing 1-h exercise (30-min cycling, 30-min running) at 75%-80% maximal HR (EX, 2661 ± 783 kJ) or 1-h supine rest (REST, 310 ± 58 kJ) 3 h after lunch. Participants were provided a food pack (pasta meal/snacks) for consumption after exercise (outside laboratory). Appetite was measured regularly, and meal and 24-h energy intake were quantified.Ad libitum energy intake was greater during EX at lunch (EX, 3450 ± 1049 kJ; REST, 3103 ± 927 kJ; P = 0.004), but similar between trials at breakfast (EX, 2656 ± 1291 kJ; REST, 2484 ± 1156 kJ; P = 0.648) and dinner (EX, 6249 ± 2216 kJ; REST, 6240 ± 2585 kJ; P = 0.784). Total 24-h energy intake was similar between trials (P = 0.388), meaning that relative energy intake (24-h energy intake minus EX/REST energy expenditure) was reduced during EX (EX, 9694 ± 3313 kJ; REST, 11,517 ± 4023 kJ; P = 0.004).Energy intake seems to be increased in anticipation of, rather than in response to, aerobic exercise, but the increase was insufficient to compensate for energy expended during exercise, meaning that aerobic exercise reduced energy balance relative to rest.

The practice of rapid weight loss (RWL) in mixed martial arts (MMA) is an increasing concern but data remain scarce. The aim of this study was to investigate the prevalence, magnitude, methods, and influencers of RWL in professional and amateur MMA athletes. MMA athletes (N = 314; 287 men and 27 women) across nine weight categories (strawweight to heavyweight), completed a validated questionnaire adapted for this sport. Sex-specific data were analyzed, and subgroup comparisons were made between athletes competing at professional and amateur levels. Most athletes purposefully reduced body weight for competition (men: 97.2%; women: 100%). The magnitude of RWL in 1 week prior to weigh-in was significantly greater for professional athletes compared with those competing at amateur level (men: 5.9% vs. 4.2%; women: 5.0% vs. 2.1% of body weight; p p always” or “sometimes” used water loading (72.9%), restricting fluid intake (71.3%), and sweat suits (55.4%) for RWL. Coaches were cited as the primary source of influence on RWL practices (men: 29.3%; women: 48.1%). There is a high reported prevalence of RWL in MMA, at professional and amateur levels. Our findings, constituting the largest inquiry to date, call for urgent action from MMA organizations to safeguard the health and well-being of athletes competing in this sport.

In many situations, meals are planned (i.e. what and how much) before they are eaten, but how exercise influences this planning is unknown. Therefore, this study investigated whether anticipation of an exercise session alters food intake planned for post-exercise. Forty (16 male) regular exercisers (mean ± SD; age 23.3 ± 5.6 y, BMI 22.7 ± 3.3 kg/m2, body fat 25.6 ± 7.6%) completed the study. Subjects arrived ≥3 h post-prandial and were given two hypothetical scenarios for the following day: 1) morning rest (REST), or 2) morning rest with the addition of 1 h of hard aerobic exercise at 10:00–11:00 (EXERCISE). For each scenario subjects had to plan their lunch, to consume at 12:00, by serving themselves cheesy tomato pasta and chocolate buttons. Scenarios were randomised and separated by 5 min and foods were not consumed. EXERCISE increased total energy served by 24% (EXERCISE 3308 ± 1217 kJ; REST 2663 ± 924 kJ; P

Bin Naharudin, MN, Yusof, A, Shaw, H, Stockton, M, Clayton, DJ, and James, LJ. Breakfast omission reduces subsequent resistance exercise performance. J Strength Cond Res 33(7): 1766-1772, 2019-Although much research has examined the influence of morning carbohydrate intake (i.e., breakfast) on endurance performance, little is known about its effects on performance in resistance-type exercise. Sixteen resistance-trained men (age 23 ± 4 years, body mass 77.56 ± 7.13 kg, and height 1.75 ± 0.04 m) who regularly (≥3 day/wk) consumed breakfast completed this study. After assessment of 10 repetition maximum (10RM) and familiarization process, subjects completed 2 randomized trials. After an overnight fast, subjects consumed either a typical breakfast meal (containing 1.5 g of carbohydrate/kg; breakfast consumption [BC]) or a water-only breakfast (breakfast omission [BO]). Two hours later, subjects performed 4 sets to failure of back squat and bench press at 90% of their 10RM. Sensations of hunger, fullness, desire to eat, and prospective food consumption were collected before, as well as immediately, 1 hour and 2 hours after BC/BO using 100-mm visual analogue scales. Total repetitions completed were lower during BO for both back squat (BO: 58 ± 11 repetitions; BC: 68 ± 14 repetitions; effect size [ES] = 0.98; p < 0.001) and bench press (BO: 38 ± 5 repetitions; BC: 40 ± 5 repetitions; ES = 1.06; p < 0.001). Fullness was greater, whereas hunger, desire to eat, and prospective food consumption were lower after a meal for BC compared with BO (p < 0.001). The results of this study demonstrate that omission of a pre-exercise breakfast might impair resistance exercise performance in habitual breakfast consumers. Therefore, consumption of a high-carbohydrate meal before resistance exercise might be a prudent strategy to help maximize performance.

Objectives Ingested ketogenic agents offer the potential to enhance endurance performance via the provision of an alternative exogenous, metabolically efficient, glycogen-sparing fuel (i.e. ketone bodies). This study aimed to assess the impact of combined carbohydrate and 1,3-butanediol (CHO-BD) supplementation on endurance performance, blood beta-hydroxybutyrate (βHB) concentration and glycolytic activity, in comparison to carbohydrate supplementation alone (CHO). Design Eleven male runners (age 38 ± 12 years, mass 67.3 ± 6.5 kg, height 174.5 ± 5.0 cm, V ˙ O 2 p e a k 64.2 ± 5.0 ml⋅kg−1⋅min−1) performed two experimental trials in a randomised crossover design. Methods Each trial consisted of 60 min of submaximal running, followed by a 5 km running time-trial (TT), and was performed following the ingestion of an energy matched ∼650 ml drink (CHO-BD or CHO). Results There was no difference in TT completion time between the trials (CHO: 1265 ± 93, CHO-BD: 1261 ± 96 s; p = 0.723). However, blood βHB concentration in the CHO-BD trial was at least double that of the CHO trial at all time points following supplementation (p Conclusions An energy matched CHO-BD supplementation drink raised βHB concentration and acutely lowered blood lactate concentration, without enhancing 5 km TT running performance.

This study examined sweat rate, sweat sodium concentration [Na+], and ad-libitum carbohydrate and fluid intakes in elite female soccer players during training (n = 19) and a match (n = 8); eight completed both for comparisons. Body mass (kg) was obtained before and after exercise to calculate sweat rate. The sweat [Na+] was determined from absorbent patches on the thigh or back. Sweat rate, percentage body mass change, and sweat [Na+] for 19 players during training were 0.47 ± 0.19 L·h−1, +0.19 ± 0.65%, and 28 ± 10 mmol·L−1, respectively. Sweat rate was higher during a match (0.98 ± 0.34 L·h−1) versus training (0.49 ± 0.26 L·h−1, p = 0.007). Body mass losses were greater post-match (−1.12 ± 0.86%) than training (+0.29 ± 0.34%, p = 0.003). Sweat [Na+] was similar for training (29 ± 9 mmol·L−1) and a match (35 ± 9 mmol·L−1) (p = 0.215). There were no differences in match versus training carbohydrate intakes (2.0 ± 2.3 g·h−1, 0.9 ± 1.5 g·h−1, respectively, p = 0.219) or fluid intakes (0.71 ± 0.30 L·h−1, 0.53 ± 0.21 L·h−1, respectively, p = 0.114). In conclusion, female soccer players’ sweat rates were higher during a match than during training, and carbohydrate intakes were below recommendations for matches and training.

This study aimed to assess the effects of consuming a very-low-energy placebo breakfast on subsequent appetite and lunch energy intake.Fourteen healthy males consumed water-only (WAT), very-low-energy, viscous placebo (containing water, low-calorie flavoured squash, and xanthan gum; ~ 16 kcal; PLA), and whole-food (~ 573 kcal; FOOD) breakfasts in a randomised order. Subjects were blinded to the energy content of PLA and specific study aims. Venous blood samples were collected pre-breakfast, 60- and 180-min post-breakfast to assess plasma acylated ghrelin and peptide tyrosine tyrosine concentrations. Subjective appetite was measured regularly, and energy intake was assessed at an ad libitum lunch meal 195-min post-breakfast.Lunch energy intake was lower during FOOD compared to WAT (P 0.05), with no further differences between trials (P ≥ 0.132). Cumulative energy intake (breakfast plus lunch) was lower during PLA (1078 ± 274 kcal) and WAT (1093 ± 249 kcal), compared to FOOD (1554 ± 301 kcal; P 0.001). Total area under the curve (AUC) for hunger, desire to eat and prospective food consumption were lower, and fullness was greater during PLA and FOOD compared to WAT (P 0.05). AUC for hunger was lower during FOOD compared to PLA (P 0.05). During FOOD, acylated ghrelin was suppressed compared to PLA and WAT at 60 min (P 0.05), with no other hormonal differences between trials (P ≥ 0.071).Consuming a very-low-energy placebo breakfast does not alter energy intake at lunch but may reduce cumulative energy intake across breakfast and lunch and attenuate elevations in subjective appetite associated with breakfast omission.NCT04735783, 2nd February 2021, retrospectively registered.

Cow’s milk is a naturally nutrient-dense foodstuff. A significant source of many essential nutrients, its inclusion as a component of a healthy balanced diet has been long recommended. Beyond milk’s nutritional value, an increasing body of evidence illustrates cow’s milk may confer numerous benefits related to health. Evidence from adult populations suggests that cow’s milk may have a role in overall dietary quality, appetite control, hydration and cognitive function. Although evidence is limited compared with the adult literature, these benefits may be echoed in recent paediatric studies. This article, therefore, reviews the scientific literature to provide an evidence-based evaluation of the associated health benefits of cow’s milk consumption in primary-school-aged children (4–11 years). We focus on seven key areas related to nutrition and health comprising nutritional status, hydration, dental and bone health, physical stature, cognitive function, and appetite control. The evidence consistently demonstrates cow’s milk (plain and flavoured) improves nutritional status in primary-school-aged children. With some confidence, cow’s milk also appears beneficial for hydration, dental and bone health and beneficial to neutral concerning physical stature and appetite. Due to conflicting studies, reaching a conclusion has proven difficult concerning cow’s milk and cognitive function; therefore, a level of caution should be exercised when interpreting these results. All areas, however, would benefit from further robust investigation, especially in free-living school settings, to verify conclusions. Nonetheless, when the nutritional-, physical- and health-related impact of cow’s milk avoidance is considered, the evidence highlights the importance of increasing cow’s milk consumption.

Background: Preexercise food intake enhances exercise performance due, in part, to the provision of exogenous carbohydrate. Food intake also suppresses hunger, but the specific influence of hunger on exercise performance has not been investigated. This study aimed to manipulate hunger by altering preexercise meal viscosity to examine whether hunger influences performance. Methods: Sixteen resistance-trained males completed 2 experimental trials ingesting either high viscosity semisolid (SEM) and low viscosity liquid (LIQ) carbohydrate-containing meals 2 hours before performing 4 sets of back squat (85 [22] kg) and bench press (68 [13] kg) to failure at 90% 10-repetition maximum. Subjective hunger/fullness as well as plasma concentrations of glucose, insulin, ghrelin, and peptide tyrosine–tyrosine were measured before and periodically after the meal. Repetitions completed in sets were used to determine exercise performance. Results: Hunger was lower, and fullness was greater during SEM compared with LIQ immediately before and during exercise (P P = .001) with no difference in bench press repetitions (SEM 48 [11]; LIQ 48 [10] repetitions; P = .621). Postprandial glucose concentrations were greater during LIQ (12% increase in peak glucose) but were similar throughout exercise. Conclusion: This study demonstrates that exercise performance in back squat was increased in the SEM trial concomitant to a reduction in hunger. Therefore, this study provides novel data that suggest that exercise performance might be influenced by hunger, at least for resistance exercise.

Purpose Whilst there is evidence to suggest that hypohydration caused by physical work in the heat increases renal injury, whether this is the case during exercise in temperate conditions remains unknown. This study investigated the effect of manipulating hydration status during high-intensity intermittent running on biomarkers of renal injury. Methods After familiarisation, 14 males (age: 33 ± 7 years; V̇O2peak: 57.1 ± 8.6 ml/kg/min; mean ± SD) completed 2 trials in a randomised cross-over design, each involving 6, 15 min blocks of shuttle running (modified Loughborough Intermittent Shuttle Test protocol) in temperate conditions (22.3 ± 1.0 °C; 47.9 ± 12.9% relative humidity). During exercise, subjects consumed either a volume of water equal to 90% of sweat losses (EU) or 75 mL water (HYP). Body mass, blood and urine samples were taken pre-exercise (baseline/pre), 30 min post-exercise (post) and 24 h post-baseline (24 h). Results Post-exercise, body mass loss, serum osmolality and urine osmolality were greater in HYP than EU (P ≤ 0.024). Osmolality-corrected urinary kidney injury molecule-1 (uKIM-1) concentrations were increased post-exercise (P ≤ 0.048), with greater concentrations in HYP than EU (HYP: 2.76 [1.72–4.65] ng/mOsm; EU: 1.94 [1.1–2.54] ng/mOsm; P = 0.003; median [interquartile range]). Osmolality-corrected urinary neutrophil gelatinase-associated lipocalin (uNGAL) concentrations were increased post-exercise (P P = 0.073). Conclusion These results suggest that hypohydration produced by high-intensity intermittent running increases renal injury, compared to when euhydration is maintained, and that the site of this increased renal injury is at the proximal tubules.

Hypohydration increases physiological strain and reduces physical and technical soccer performance, but there are limited data on how fluid balance responses change between different types of sessions in professional players. This study investigated sweat and fluid/carbohydrate intake responses in elite male professional soccer players training at low and high intensities in cool and hot environments. Fluid/sodium (Na+) losses and ad-libitum carbohydrate/fluid intake of fourteen elite male soccer players were measured on four occasions: cool (wet bulb globe temperature (WBGT): 15 &plusmn, 7 &deg, C, 66 &plusmn, 6% relative humidity (RH)) low intensity (rating of perceived exertion (RPE) 2&ndash, 4, m&middot, min&minus, 1 40&ndash, 46) (CL), cool high intensity (RPE 6&ndash, 8, m&middot, 1 82&ndash, 86) (CH), hot (29 &plusmn, 1 &deg, C, 52 &plusmn, 7% RH) low intensity (HL), hot high intensity (HH). Exercise involved 65 &plusmn, 5 min of soccer-specific training. Before and after exercise, players were weighed in minimal clothing. During training, players had ad libitum access to carbohydrate beverages and water. Sweat [Na+] (mmol&middot, L&minus, 1), which was measured by absorbent patches positioned on the thigh, was no different between conditions, CL: 35 &plusmn, 9, CH: 38 &plusmn, 8, HL: 34 &plusmn, 70.17, HH: 38 &plusmn, 8 (p = 0.475). Exercise intensity and environmental condition significantly influenced sweat rates (L&middot, h&minus, 1), CL: 0.55 &plusmn, 0.20, CH: 0.98 &plusmn, 0.21, HL: 0.81 &plusmn, 0.17, HH: 1.43 &plusmn, 0.23 (p =0.001), and percentage dehydration (p &lt, 0.001). Fluid intake was significantly associated with sweat rate (p = 0.019), with no players experiencing hypohydration &gt, 2% of pre-exercise body mass. Carbohydrate intake varied between players (range 0&ndash, 38 g&middot, 1), with no difference between conditions. These descriptive data gathered on elite professional players highlight the variation in the hydration status, sweat rate, sweat Na+ losses, and carbohydrate intake in response to training in cool and hot environments and at low and high exercise intensities.

This study investigated metabolic, endocrine, appetite and mood responses to a maximal eating occasion in fourteen men (mean: age 28 (sd5) years, body mass 77·2 (sd6·6) kg and BMI 24·2 (sd2·2) kg/m2) who completed two trials in a randomised crossover design. On each occasion, participants ate a homogenous mixed-macronutrient meal (pizza). On one occasion, they ate until ‘comfortably full’ (ad libitum) and on the other, until they ‘could not eat another bite’ (maximal). Mean energy intake was double in the maximal (13 024 (95 % CI 10 964, 15 084) kJ; 3113 (95 % CI 2620, 3605) kcal) compared with thead libitumtrial (6627 (95 % CI 5708, 7547) kJ; 1584 (95 % CI 1364, 1804) kcal). Serum insulin incremental AUC (iAUC) increased approximately 1·5-fold in the maximal compared withad libitumtrial (mean:ad libitum43·8 (95 % CI 28·3, 59·3) nmol/l × 240 min and maximal 67·7 (95 % CI 47·0, 88·5) nmol/l × 240 min,P< 0·01), but glucose iAUC did not differ between trials (ad libitum94·3 (95 % CI 30·3, 158·2) mmol/l × 240 min and maximal 126·5 (95 % CI 76·9, 176·0) mmol/l × 240 min,P= 0·19). TAG iAUC was approximately 1·5-fold greater in the maximalv.ad libitumtrial (ad libitum98·6 (95 % CI 69·9, 127·2) mmol/l × 240 min and maximal 146·4 (95 % CI 88·6, 204·1) mmol/l × 240 min,P< 0·01). Total glucagon-like peptide-1, glucose-dependent insulinotropic peptide and peptide tyrosine–tyrosine iAUC were greater in the maximal compared withad libitumtrial (P< 0·05). Total ghrelin concentrations decreased to a similar extent, but AUC was slightly lower in the maximalv.ad libitumtrial (P= 0·02). There were marked differences on appetite and mood between trials, most notably maximal eating caused a prolonged increase in lethargy. Healthy men have the capacity to eat twice the energy content required to achieve comfortable fullness at a single meal. Postprandial glycaemia is well regulated following initial overeating, with elevated postprandial insulinaemia probably contributing.

Exercise intensity affects many potential postprandial responses, but there is limited information on the influence of exercise modality. Therefore, the aim of this study was to investigate if the nature of exercise at two different intensities would affect gastric emptying rate (GER), appetite and metabolic responses following ingestion of a semi-solid meal. Twelve healthy men completed, in a random order, four 60-min cycles at 60% VO2peak (MOD), 40% VO2peak (LOW) and in a continuous (CON) or intermittent (INT) manner. INT consisted of 20 &times, 1-min exercise bouts with 2-min rest breaks. INT and CON were matched for total work output at each intensity. GER of the post-exercise meal was measured for 2 h using the 13C-breath method. Blood glucose, substrate utilisation and appetite ratings were measured at regular intervals throughout all trials and 24-h energy intake (EI) post-trials was assessed. GER-Delta over Baseline (DOB) was lower (p &lt, 0.05) on MOD-INT vs. MOD-CON from 30&ndash, 120 min post-meal. Blood glucose was higher mid-exercise (p &lt, 0.05) on MOD-INT vs. MOD-CON. Although post-exercise LOW-CON was significantly higher than LOW-INT (p &lt, 0.05), blood glucose was also higher 30-min post-meal ingestion on both CON trials compared to INT (p &lt, 0.001). No interaction effect was observed for perceived appetite responses 2 h after meal ingestion (all p &gt, 0.05). 24-h post-trial EI was similar between LOW-CON vs. LOW-INT (p &gt, 0.05), although MOD-INT vs. MOD-CON 3500 &plusmn, 1419 vs. 2556 &plusmn, 989 kCal: p &lt, 0.001 was elevated. In summary, MOD-INT exercise delays GER without stimulating perceived appetite in the 2 h period after meal ingestion, although EI was greater in the 24-h post-trial.

This study investigated whether supplementation with nitrate-rich beetroot juice (BR) can improve high-intensity intermittent running performance in trained males in normoxia and different doses of normobaric hypoxia. Eight endurance-trained males (, 62 ± 6 ml·kg−1·min−1) completed repeated 90 s intervals at 110% of peak treadmill velocity, from an initial step incremental test, interspersed by 60 s of passive recovery until exhaustion (Tlim). Participants completed the first three experimental trials during days 3, 5, and 7 of BR or nitrate-depleted beetroot juice (PLA) supplementation and completed the remaining experimental visits on the alternative supplement following at least 7 days of washout. The fraction of inspired oxygen during visits 1–3 was either 0.209, 0.182, or 0.157, equivalent to an altitude of 0, 1,200, and 2,400 m, respectively, and this order was replicated on visits 4–6. Arterial oxygen saturation declined dose dependently as fraction of inspired oxygen was lowered (p p lim between PLA and BR at 0 m (445 [324, 508] and 410 [368, 548] s); 1,200 m (341 [270, 390] and 332 [314, 356] s); or 2,400 m (233 [177, 373] and 251 [221, 323] s) (median and [interquartile range]; p > .05). The findings from this study suggest that short-term BR supplementation does not improve high-intensity intermittent running performance in endurance-trained males in normoxia or at doses of normobaric hypoxia that correspond to altitudes at which athletes typically train while on altitude training camps.

Acute kidney injury (AKI) incidence (diagnosed by changes in serum creatinine [Cr]) following prolonged endurance events has been reported to be anywhere from 4 to 85%, and hypohydration may contribute to this. Whilst an increase in serum Cr indicates impaired kidney function, this might be influenced by muscle damage. Therefore, the use of other AKI biomarkers which can detect renal tubular injury may be more appropriate. The long-term consequences of AKI are not well understood, but there are some potential concerns of an increased subsequent risk of chronic kidney disease (CKD). Therefore, this brief review explores the effects of exercise training/competition on novel AKI biomarkers and the potential influence of fluid intake. The increase in novel AKI biomarkers following prolonged endurance events suggests renal tubular injury. This is likely due to the long duration and relatively high exercise intensity, producing increased sympathetic tone, body temperature, hypohydration, and muscle damage. Whilst muscle damage appears to be an important factor in the pathophysiology of exercise-associated AKI, it may require coexisting hypohydration. Fluid intake seems to play a role in exercise-associated AKI, as maintaining euhydration with water ingestion during simulated physical work in the heat appears to attenuate rises in AKI biomarkers. The composition of fluid intake may also be important, as high-fructose drinks have been shown to exacerbate AKI biomarkers. However, it is yet to be seen if these findings are applicable to athletes performing strenuous exercise in a temperate environment. Additionally, further work should examine the effects of repeated bouts of strenuous exercise on novel AKI biomarkers.

PURPOSE: To determine whether the pattern of carbohydrate sports drink ingestion during prolonged sub-maximal running affects exogenous carbohydrate oxidation rates and gastrointestinal (GI) comfort. METHODS: Twelve well-trained male runners (27 ± 7 y, 67.9 ± 6.7 kg, V[Combining Dot Above]O2peak: 68 ± 7 mL·kg·min) completed two exercise trials of 100 min steady state running at 70% V[Combining Dot Above]O2peak. In each of the trials, 1 L of a 10% dextrose solution, enriched with [U-C] glucose, was consumed as either 200 mL every 20 min (CHO-20) or 50 mL every 5 min (CHO-5). Expired breath and venous blood samples were collected at rest and every 20 min during exercise. Subjective scales of GI comfort were recorded at regular intervals. RESULTS: Average exogenous carbohydrate oxidation rates were 23% higher during exercise in CHO-20 (0.38 ± 0.11 vs. 0.31 ± 0.11 g·min; P=0.017). Peak exogenous carbohydrate oxidation was also higher in CHO-20 (0.68 ± 0.14 g·min vs. 0.61 ± 0.14 g·min; P=0.004). During exercise, total carbohydrate oxidation (CHO-20: 2.15 ± 0.47; CHO-5: 2.23 ± 0.45 g·min, P=0.412) and endogenous carbohydrate oxidation (CHO-20: 1.78 ± 0.45; CHO-5: 1.92 ± 0.40 g·min; P=0.148) were not different between trials. Average serum glucose (P=0.952) and insulin (P=0.373) concentrations were not different between trials. There were no differences in reported symptoms of GI comfort and stomach bloatedness (P>0.05), with only 3% of reported scores classed as severe (>5 out of 10). CONCLUSION: Ingestion of a larger volume of carbohydrate solution at less frequent intervals during prolonged submaximal running increased exogenous carbohydrate oxidation rates. Neither drinking pattern resulted in increased markers of GI discomfort to a severe level.

Purpose Intermittent energy restriction commonly refers to ad libitum energy intake punctuated with 24 h periods of severe energy restriction. This can improve markers of metabolic health but the effects on bone metabolism are unknown. This study assessed how 24 h severe energy restriction and subsequent refeeding affected markers of bone turnover. Methods In a randomised order, 16 lean men and women completed 2, 48 h trials over 3 days. On day 1, participants consumed a 24 h diet providing 100% [EB: 9.27 (1.43) MJ] or 25% [ER: 2.33 (0.34) MJ] of estimated energy requirements. On day 2, participants consumed a standardised breakfast (08:00), followed by an ad libitum lunch (12:00) and dinner (19:30). Participants then fasted overnight, returning on day 3. Plasma concentrations of C-terminal telopeptide of type I collagen (CTX), procollagen type 1 N-terminal propeptide (P1NP) and parathyroid hormone (PTH) were assessed as indices of bone metabolism after an overnight fast on days 1–3, and for 4 h after breakfast on day 2. Results There were no differences between trials in fasting concentrations of CTX, P1NP or PTH on days 1–3 (P > 0.512). During both trials, consuming breakfast reduced CTX between 1 and 4 h (P P P = 0.773) Postprandial responses for CTX (P = 0.157), P1NP (P = 0.148) and PTH (P = 0.575) were not different between trials. Ad libitum energy intake on day 2 was greater on ER [12.62 (2.46) MJ] than EB [11.91 (2.49) MJ]. Conclusions Twenty-four hour severe energy restriction does not affect markers of bone metabolism.

Objectives: Short periods of excessive consumption of indulgent high-fat foods are common in Western society, but the effect this has on bone is unknown. The aim of this pilot study was to explore how a 7-d hyperenergetic, high-fat diet affects candidate biomarkers of bone metabolism.\ud \ud Methods: The study included 12 healthy men with a mean age of 24 y (SD = 4 y) and body mass index (BMI) of 24.1 kg/m2 (SD = 1.5). The men consumed a 7-d hyperenergetic, high-fat diet (HE-HFD; 20.9 [SD = 0.8] MJ; 65% total energy as fat) and a control (CON) diet (10.9 [SD = 2] MJ; 36% total energy as fat), in randomized, crossover order, with each trial separated by 3 wk. Markers of bone formation (P1NP) and bone resorption (CTx) were measured at baseline and after 1, 3, and 7 d of each diet. Bone metabolic responses were analyzed using two-factor repeated-measures analysis of variance and subsequent pairwise comparisons.\ud \ud Results: There was a main effect of time (P < 0.05), but no trial (P = 0.270) or time- × -trial interaction (P = 0.693) effects for plasma concentrations of CTx. Mean CTx concentrations did not differ between trials (CON: 0.97 ng/mL [SD = 0.39]; HE-HFD: 1.03 ng/mL [SD = 0.22]; P = 0.225). There was a main effect of trial (P < 0.01), but no time (P = 0.138) or trial- × -interaction (P = 0.179) effects for plasma concentrations of P1NP. Mean P1NP concentrations were lower during the HE-HFD (61.79 ng/mL [SD = 26.54]) than during the CON diet (77.89 ng/mL [SD = 28.71]; P < 0.01).\ud \ud Conclusions: A 7-d hyperenergetic, high-fat diet reduces a marker of bone formation but does not affect a marker of bone resorption. This pilot study suggested that short periods of excessive energy and fat consumption may detrimentally affect bone health.

Post-exercise recovery is a multi-facetted process that will vary depending on the nature of the exercise, the time between exercise sessions and the goals of the exerciser. From a nutritional perspective, the main considerations are: (1) optimisation of muscle protein turnover; (2) glycogen resynthesis; (3) rehydration; (4) management of muscle soreness; (5) appropriate management of energy balance. Milk is approximately isotonic (osmolality of 280–290 mosmol/kg), and the mixture of high quality protein, carbohydrate, water and micronutrients (particularly sodium) make it uniquely suitable as a post-exercise recovery drink in many exercise scenarios. Research has shown that ingestion of milk post-exercise has the potential to beneficially impact both acute recovery and chronic training adaptation. Milk augments post-exercise muscle protein synthesis and rehydration, can contribute to post-exercise glycogen resynthesis, and attenuates post-exercise muscle soreness/function losses. For these aspects of recovery, milk is at least comparable and often out performs most commercially available recovery drinks, but is available at a fraction of the cost, making it a cheap and easy option to facilitate post-exercise recovery. Milk ingestion post-exercise has also been shown to attenuate subsequent energy intake and may lead to more favourable body composition changes with exercise training. This means that those exercising for weight management purposes might be able to beneficially influence post-exercise recovery, whilst maintaining the energy deficit created by exercise.

PURPOSE: To examine the effect on short duration, high intensity cycling time trial performance when a semi-solid breakfast containing carbohydrate or a taste and texture matched placebo is ingested 90 minutes pre-exercise compared to a water control. METHODS: Thirteen well trained cyclists (25 ± 8 years, 71.1 ± 5.9 kg, 1.76 ± 0.04 m, 383 ± 46 Wmax, VO2peak 4.42 ± 0.53 L·min-1) performed three experimental trials examining breakfast ingestion 90 minutes before a 10 minute steady state cycle (60% Wmax) and a ~20 minute time trial (to complete a workload target of 376 ± 36 kJ). Subjects consumed either water (WAT), a semi-solid carbohydrate breakfast (2 g carbohydrate·kg-1 body mass; CHO) or a taste and texture matched placebo (PLA). Blood lactate and glucose concentrations were measured periodically throughout the rest and exercise periods. RESULTS: The time trial was completed quicker in CHO (1120 ± 69 s; P=0.006) and PLA (1112 ± 50 s; P=0.030) compared to WAT (1146 ± 74 s). Ingestion of carbohydrate caused an increase in blood glucose concentration throughout the rest period in CHO (peak at 30 minutes rest: 7.37 ± 1.10 mmol·l-1; P

Objectives This study investigated the influence of a moderate caffeine dose on endurance cycle performance and thermoregulation during prolonged exercise in high ambient temperature. Design Double-blind cross-over study. Methods Eight healthy, recreationally active males (mean ± SD; age: 22 ± 1 years; body mass: 71.1 ± 8.5 kg; VO2peak: 55.9 ± 5.8 mL kg−1 min−1; Wmax: 318 ± 37 W) completed one VO2peak test, one familiarisation trial and two experimental trials. After an overnight fast, participants ingested a placebo or a 6 mg kg−1 caffeine dose 60 min before exercise. The exercise protocol consisted of 60 min of cycle exercise at 55% Wmax, followed by a 30 min performance task (total kJ produced) in 30 °C and 50% RH. Results Performance was enhanced (Cohen’s d effect size = 0.22) in the caffeine trial (363.8 ± 47.6 kJ) compared with placebo (353.0 ± 49.0 kJ; p = 0.004). Caffeine did not influence core (p = 0.188) or skin temperature (p = 0.577) during exercise. Circulating prolactin (p = 0.572), cortisol (p = 0.842) and the estimated rates of fat (p = 0.722) and carbohydrate oxidation (p = 0.454) were also similar between trial conditions. Caffeine attenuated perceived exertion during the initial 60 min of exercise (p = 0.033), with no difference in thermal stress across trials (p = 0.911). Conclusions Supplementation with 6 mg kg−1 caffeine improved endurance cycle performance in a warm environment, without differentially influencing thermoregulation during prolonged exercise at a fixed work-rate versus placebo. Therefore, moderate caffeine doses which typically enhance performance in temperate environmental conditions also appear to benefit endurance performance in the heat.

The purpose of this study was to examine the efficacy of water and a 50 mmol/L NaCl solution on postexercise rehydration when a standard meal was consumed during rehydration. Eight healthy participants took part in two experimental trials during which they lost 1.5 ± 0.4% of initial body mass via intermittent exercise in the heat. Participants then rehydrated over a 60-min period with water or a 50 mmol/L NaCl solution in a volume equivalent to 150% of their body mass loss during exercise. In addition, a standard meal was ingested during this time which was equivalent to 30% of participants predicted daily energy expenditure. Urine samples were collected before and after exercise and for 3 hr after rehydration. Cumulative urine volume (981 ± 458 ml and 577 ± 345 mL; p = .035) was greater, while percentage fluid retained (50 ± 20% and 70 ± 21%; p = .017) was lower during the water compared with the NaCl trial respectively. A high degree of variability in results was observed with one participant producing 28% more urine and others ranging from 18–83% reduction in urine output during the NaCl trial. The results of this study suggest that after exercise induced dehydration, the ingestion of a 50 mmol/L NaCl solution leads to greater fluid retention compared with water, even when a meal is consumed postexercise. Furthermore, ingestion of plain water may be effective for maintenance of fluid balance when food is consumed in the rehydration period.

Background: Few studies have investigated the effect of hydration status on appetite for food in healthy adults. Prior work suggests hydration status does not alter appetite or energy intake, with mixed findings regarding appetite hormone secretion. However, an extensive investigation into both the psychological and physiological appetitive responses to hydration status has never been conducted. Objective: To investigate the effect of hydration status on multiple facets of appetite.Design: After 3 days pre-trial standardization, a range of appetite tasks were conducted when hypohydrated (HYPO) and euhydrated (EUHY) in 16 healthy participants (8 men). Hydration status was manipulated via dehydration in a heat tent for 60 min and subsequent fluid restriction (HYPO) or replacement (EUHY). The next day, a food reward computer task was completed followed by an ad libitum pasta meal. Pre- and post-prandial visual analogue scales assessing hunger, fullness, and flavour desires (sweet, salty, savoury and fatty) were additionally completed. Blood samples were taken the previous day before the hydration interventions in a euhydrated state, and in the fasted and post-prandial state during HYPO and EUHY.Results: HYPO induced -1.9 ± 1.2% body mass change, compared to -0.2 ± 0.6%, with accompanying changes in markers of hypohydration which were not seen during EUHY. A higher desire for foods was associated with a higher water content but the association was weaker in EUHY compared to HYPO, (β= -0.33 mm/g of food water content, p < 0.001) in the food reward task. Visual analogue scales showed similar hunger and fullness between interventions, but during HYPO there was consistently higher thirst (average range in difference 27–32 mm across all time points) and lower fasted desire for salt (−23, 95% CI −10, −35 mm). Ad libitum energy intake (HYPO 1953 ± 742 kJ, EUHY 2027 ± 926 kJ; p = 0.542) and post-prandial ghrelin concentrations (HYPO 180 ± 65 pg mL−1, EUHY 188 ± 71 pg mL−1; p = 0.736) were similar by hydration status.Conclusions: An acute manipulation to hydration status altered desire for salt and foods of differing water contents, but did not influence energy intake at an ad libitum pasta meal. Further research should investigate whether these appetites would alter food choice.

Background: Chronic hot water immersion (HWI) confers health benefits, including a reduction in fasting blood glucose concentration. Here we investigate acute glycaemic control immediately after HWI. Methods: Ten participants (age: 25 ± 6 years, body mass: 84 ± 14 kg, height 1.85 ± 0.09 m) were immersed in water (39oC) to the neck (HWI) or sat at room temperature (CON) for 60 min. One hour afterwards they underwent an oral glucose tolerance test (OGTT), with blood collected before and after HWI/CON and during the 2 h OGTT. Results: Glucose incremental area under the curve (iAUC) during the OGTT was higher for HWI (HWI 233 ± 88, CON 156 ± 79 mmol·L-1·2h, P = 0.02). Insulin iAUC did not differ between conditions (HWI 4309 ± 3660, CON 3893 ± 3031 mU·L-1·2h, P=0.32). Core temperature increased to 38.6 ± 0.2°C during HWI, but was similar between trials during the OGTT (HWI 37.0 ± 0.2, CON 36.9 ± 0.4°C, P=0.34). Directly following HWI, plasma average adrenaline and growth hormone concentrations increased 2.7 and 10.7-fold, respectively (P < 0.001). Plasma glucagon like peptide-1, peptide YY and acylated ghrelin concentrations were not different between trials during the OGTT (P > 0.11). Conclusions: HWI increased postprandial glucose concentration to an OGTT, which was accompanied by acute elevations of stress hormones following HWI. The altered glycaemic control appears to be unrelated to changes in gut hormones during the OGTT.

Glucoregulatory diseases, such as type 2 diabetes are currently a key public health priority. Public health messages have started to include the addition of water in their dietary guidelines. Such guidelines however are not based on causal evidence pertaining to the health effects of increased water intake, but rather more heavily based upon non-causal or mechanistic data. One line of thinking linking fluid intake and health is that hypohydration induces elevated blood concentrations of arginine vasopressin (AVP). Research in the 1970s and 1980s implicated AVP in glucoregulation, supported by observational evidence. This important area of research subsequently appeared to stop until the 21st century during which interest in hypertonic saline infusion studies, animal AVP receptor knockout models, dietary and genetic associations, and human interventions manipulating hydration status have resurged. This narrative review briefly describes and critically evaluates the usefulness of the current AVP-glucoregulatory research. We offer suggestions on how to test the independent glucoregulatory effects of body water changes compared to elevated circulating AVP concentrations, such as investigating hydration manipulations using 3,4-Methylenedioxymethamphetamine. Whilst much research is still needed before making firm conclusions, the current evidence suggests that although AVP may be partially implicated in glucoregulation, more ecologically valid models using human participants suggests this effect might be independent of the hydration status. The key implication of this hypothesis if confirmed in future research is that manipulating the hydration status to reduce circulating AVP concentrations may not be an effective method to improve glucoregulatory health.

Context The mechanisms responsible for dietary fat-induced insulin resistance of skeletal muscle and its microvasculature are only partially understood. Objective To determine the impact of high-fat overfeeding on postprandial glucose fluxes, muscle insulin signaling, and muscle microvascular endothelial nitric oxide synthase (eNOS) content and activation. Design Fifteen non-obese volunteers consumed a high-fat (64%) high-energy (+47%) diet for 7 days. Experiments were performed before and after the diet. Stable isotope tracers were used to determine glucose fluxes in response to carbohydrate plus protein ingestion. Muscle insulin signaling was determined as well as the content and activation state of muscle microvascular eNOS. Results High-fat overfeeding impaired postprandial glycemic control as demonstrated by higher concentrations of glucose (+11%; P = 0.004) and insulin (+19%; P = 0.035). Carbohydrate plus protein ingestion suppressed endogenous glucose production to a similar extent before and after the diet. Conversely, high-fat overfeeding reduced whole-body glucose clearance (–16%; P = 0.021) and peripheral insulin sensitivity (–26%; P = 0.006). This occurred despite only minor alterations in skeletal muscle insulin signaling. High-fat overfeeding reduced eNOS content in terminal arterioles (P = 0.017) and abolished the increase in eNOS Ser1177 phosphorylation that was seen after carbohydrate plus protein ingestion. Conclusion High-fat overfeeding impaired whole-body glycemic control due to reduced glucose clearance, not elevated endogenous glucose production. The finding that high-fat overfeeding abolished insulin-mediated eNOS Ser1177 phosphorylation in the terminal arterioles suggests that impairments in the vasodilatory capacity of the skeletal muscle microvasculature may contribute to early dietary fat-induced impairments in glycemic control.

Background: Intermittent severe energy restriction (SER) can induce substantial weight loss, but the appetite regulatory responses to SER are unknown and may dictate long-term dietary adherence.\ud \ud Objective: We determined the effect of 24-h SER on appetite regulation, metabolism, and energy intake.\ud \ud Design: Eighteen lean men and women completed two 3-d trials in randomized, counterbalanced order. On day 1 subjects consumed standardized diets containing 100% (mean 6 SD: 9.3 6 1.3 MJ; energy balance) or 25% [2.3 6 0.3 MJ; energy restriction (ER)] of energy requirements. On day 2, a standardized breakfast was consumed, with plasma concentrations of acylated ghrelin, glucagon-like peptide 1, insulin, glucose, and nonesterified fatty acids determined for 4 h. Ad libitum energy intake was assessed at lunch and dinner with subjective appetite and resting metabolism assessed throughout. On day 3, ad libitum energy intake was assessed at breakfast and by weighed food records.\ud \ud Results: Energy intake was 7% greater on day 2 (P

Purpose - Protein consumption after resistance exercise potentiates muscle protein synthesis, but its effects on subsequent appetite in this context are unknown. This study examined appetite and energy intake following consumption of protein- and carbohydrate-containing drinks after resistance exercise.\ud \ud Methods - After familiarisation, 15 resistance training males (age 21 ± 1 years, body mass 78.0 ± 11.9 kg, stature 1.78 ± 0.07 m) completed two randomised, double-blind trials, consisting of lower-body resistance exercise, followed by consumption of a whey protein (PRO 23.9 ± 3.6 g protein) or dextrose (CHO 26.5 ± 3.8 g carbohydrate) drink in the 5 min post-exercise. An ad libitum meal was served 60 min later, with subjective appetite measured throughout. Drinks were flavoured and matched for energy content and volume. The PRO drink provided 0.3 g/kg body mass protein.\ud \ud Results - Ad libitum energy intake (PRO 3742 ± 994 kJ; CHO 4172 ± 1132 kJ; P = 0.007) and mean eating rate (PRO 339 ± 102 kJ/min; CHO 405 ± 154 kJ/min; P = 0.009) were lower during PRO. The change in eating rate was associated with the change in energy intake (R = 0.661, P = 0.007). No interaction effects were observed for subjective measures of appetite. The PRO drink was perceived as creamier and thicker, and less pleasant, sweet and refreshing (P < 0.05).\ud \ud Conclusion - These results suggest whey protein consumption after resistance exercise reduces subsequent energy intake, and this might be partially mediated by a reduced eating rate. Whilst this reduced energy intake is unlikely to impair hypertrophy, it may be of value in supporting an energy deficit for weight loss.

Single bouts of land-based exercise (for example, walking, running, cycling) do not typically alter post-exercise energy intake on the day of exercise. However, anecdotal and preliminary empirical evidence suggests that swimming may increase appetite and energy intake. This study compared the acute effects of swimming on appetite, energy intake, and food preference and reward, versus exertion-matched cycling and a resting control. Thirty-two men (n = 17; mean ± SD age 24 ± 2 years, body mass index [BMI] 25.0 ± 2.6 kg/m2) and women (n = 15; age 22 ± 3 years, BMI 22.8 ± 2.3 kg/m2) completed three experimental trials (swimming, cycling, control) in a randomised, crossover design. The exercise trials involved 60-min of ‘hard’ exercise (self-selected rating of perceived exertion: 15) performed 90-min after a standardised breakfast. Food preference and reward were assessed via the Leeds Food Preference Questionnaire 15-min after exercise, whilst ad libitum energy intake was determined 30-min after exercise. The control trial involved identical procedures except no exercise was performed. Compared with control (3259 ± 1265 kJ), swimming increased ad libitum energy intake (3857 ± 1611 kJ; ES = 0.47, 95% CI of the mean difference between trials 185, 1010 kJ, P = 0.005); the magnitude of increase was smaller after cycling (3652 ± 1619 kJ; ES = 0.31, 95% CI -21, 805 kJ, P = 0.062). Ad libitum energy intake was similar between swimming and cycling (ES = 0.16, 95% CI -207, 618 kJ, P = 0.324). This effect was consistent across sexes and unrelated to food preference and reward which were similar after swimming and cycling compared with control. This study has identified an orexigenic effect of swimming. Further research is needed to identify the responsible mechanism(s), including the relevance of water immersion and water temperature per se.

Research has shown that 1) the slower a food is eaten the less food is consumed overall, and 2) context affects portion selection. This study aimed to explore whether eating rate and food intake are influenced by consuming food in 'usual' vs 'unusual' mealtime contexts. Furthermore, this study aimed to identify whether mealtime-specific appropriateness and previous consumption frequency corresponded with differences in eating rate and food intake between contexts. Seventy-eight participants were served either cheese and tomato pasta (a typical lunch food) or porridge with milk and honey (a typical breakfast food) ad libitum at both breakfast and lunch on separate days. Results showed that eating rate was slower (60.7 vs 71.2 g/min, p 0.001) and less food was consumed (404.1 vs 543.2 g, p 0.001) when participants ate cheese and tomato pasta at breakfast compared to at lunch. However, no significant differences in eating rate (54.6 vs 56.4 g/min, p = 0.75) or food intake (423.7 vs 437.7 g, p = 0.88) were found between mealtimes for porridge with milk and honey. Furthermore, differences in eating rate and food intake between contexts were not associated with differences in mealtime-specific appropriateness or previous consumption frequency. These results suggest that eating rate and ad libitum food intake are influenced by the congruency of the food-to-mealtime context; however, this effect is not associated with mealtime-specific appropriateness or previous consumption of the food. Further research should explore the implications of introducing foods at unusual mealtimes in relation to strategies for weight management.

Intermittent fasting involves alternating between severely restricted and unrestricted energy intake. Physical activity energy expenditure (PAEE) is reduced during, and energy intake is elevated after, a period of energy restriction, but whether these are altered in anticipation of energy restriction is unknown. The aim of this study was to assess energy intake and PAEE in the 24 h before severe energy restriction. In randomised, counterbalanced order, 14 healthy males completed two 48 h trials over 3 days. On day 1, participants were informed which diet they would receive on day 2; either an energy balanced diet providing 100% (2755 (159) kcal; EB) or an energy restricted diet providing 25% (691 (42) kcal; ER), of their estimated energy requirements. Throughout day 1, ad-libitum energy intake was then determined from researcher-provided breakfast (08:30–09:00), lunch (12:30–13:00), afternoon snacks (14:00–18:00) and dinner (19:30–20:00). On day 2, participants consumed their allocated diet as instructed. On day 3, ad-libitum energy intake was assessed at breakfast (08:30–09:00). PAEE was measured throughout via integrated heart-rate and accelerometry monitors. Energy intake was 6% greater on day 1 (260 (344) kcal; P < 0.05) and 14% greater at breakfast on day 3 (223 (59) kcal; P < 0.05) during ER compared to EB. PAEE was 156 (252) kcal lower on day 1 (P < 0.05) and 239 (391) lower on day 2 (P < 0.05) during ER compared to EB. These behavioural compensations meant that the energy deficit produced by 24 h severe energy restriction was attenuated by 1108 (415) kcal (46%) over the study period (P < 0.0001). These results suggest that compensatory changes in energy intake and PAEE occur before, during and after an acute 24 h period of severe energy restriction, likely lessening the energy deficit created.

Knowledge of hydration status may contribute to hypohydration-induced exercise performance decrements; therefore, this study compared blinded and unblinded hypohydration on cycling performance. Fourteen trained, nonheat-acclimated cyclists (age: 25 ± 5 yr; V̇o2peak: 63.3 ± 4.7 ml·kg−1·min−1; cycling experience: 6 ± 3 yr) were pair matched to blinded (B) or unblinded (UB) groups. After familiarization, subjects completed euhydrated (B-EUH; UB-EUH) and hypohydrated (B-HYP; UB-HYP) trials in the heat (31°C); 120-min cycling preload (50% Wpeak) and a time trial (~15 min). During the preload of all trials, 0.2 ml water·kg body mass−1 was ingested every 10 min, with additional water provided during EUH trials to match sweat losses. To blind the B group, a nasogastric tube was inserted in both trials and used to provide water in B-EUH. The preload induced similar ( P = 0.895) changes in body mass between groups (B-EUH: −0.6 ± 0.5%; B-HYP: −3.0 ± 0.5%; UB-EUH: −0.5 ± 0.3%; UB-HYP −3.0 ± 0.3%). All variables responded similarly between B and UB groups ( P ≥ 0.558), except thirst ( P = 0.004). Changes typical of hypohydration (increased heart rate, rating of perceived exertion, gastrointestinal temperature, serum osmolality and thirst, and decreased plasma volume; P ≤ 0.017) were apparent in HYP by 120 min. Time trial performance was similar between groups ( P = 0.710) and slower ( P ≤ 0.013) with HYP for B (B-EUH: 903 ± 89 s; B-HYP: 1,008 ± 121 s; −11.4%) and UB (UB-EUH: 874 ± 108 s; UB-HYP: 967 ± 170 s; −10.1%). Hypohydration of ~3% body mass impairs time trial performance in the heat, regardless of knowledge of hydration status. NEW & NOTEWORTHY This study demonstrates, for the first time, that knowledge of hydration status does not exacerbate the negative performance consequences of hypohydration when hypohydration is equivalent to ~3% body mass. This is pivotal for the interpretation of the many previous studies that have not blinded subjects to their hydration status and suggests that these previous studies are not likely to be confounded by the overtness of the methods used to induce hypohydration.

Research shows that expected satiety is highly correlated with ideal portion size, however this correspondence has not been explored when a food is presented in an ‘unusual’ (incongruous) meal context. This study's aim was to explore whether expected satiety influences portion selection to the same extent in both congruous and incongruous meal contexts. Forty participants completed two trials (one at breakfast and one at lunch) on separate days in a randomised counterbalanced order. They completed measures of expected satiety and ideal portion size for four typical breakfast foods and four typical lunch foods, using a bespoke computer program. Our results showed a significant difference between expected satiety and ideal portion size for lunch foods presented at breakfast time (an incongruous meal context; t(39) = 2.95, p = 0.02). There was no significant difference between expected satiety and ideal portion size in the other incongruous meal context (breakfast foods at lunch; t(39) = 2.10, p = 0.17) or in congruous meal contexts (breakfast foods at breakfast time, lunch foods at lunch time; both t(39) ≤ −0.15, p > 0.999). These results suggest that expected satiety does not have as strong an influence on portion selection when food is presented in an unusual context. Furthermore, in such contexts, smaller portions were selected 1) to stave off hunger until the next meal and 2) as ideal portions compared to in more usual meal contexts. Research is warranted to explore this finding further to understand its implications for weight management.

Intermittent energy restriction (IER) involves short periods of severe energy restriction interspersed with periods of adequate energy intake, and can induce weight loss. Insulin sensitivity is impaired by short-term, complete energy restriction, but the effects of IER are not well known. In randomised order, fourteen lean men (age: 25 (sd 4) years; BMI: 24 (sd 2) kg/m2; body fat: 17 (4) %) consumed 24-h diets providing 100 % (10 441 (sd 812) kJ; energy balance (EB)) or 25 % (2622 (sd 204) kJ; energy restriction (ER)) of estimated energy requirements, followed by an oral glucose tolerance test (OGTT; 75 g of glucose drink) after fasting overnight. Plasma/serum glucose, insulin, NEFA, glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic peptide (GIP) and fibroblast growth factor 21 (FGF21) were assessed before and after (0 h) each 24-h dietary intervention, and throughout the 2-h OGTT. Homoeostatic model assessment of insulin resistance (HOMA2-IR) assessed the fasted response and incremental AUC (iAUC) or total AUC (tAUC) were calculated during the OGTT. At 0 h, HOMA2-IR was 23 % lower after ER compared with EB (PPPPP=0·161), GIP (P=0·473) and FGF21 (P=0·497) tAUC were similar between trials. These results demonstrate that severe energy restriction acutely impairs postprandial glycaemic control in lean men, despite reducing HOMA2-IR. Chronic intervention studies are required to elucidate the long-term effects of IER on indices of insulin sensitivity, particularly in the absence of weight loss.

There is a paucity of data examining the effect of cutlery size on the microstructure of within-meal eating behaviour or food intake. Therefore, the present studies examined how manipulation of spoon size influenced these eating behaviour measures in lean young men. In study one, subjects ate a semi-solid porridge breakfast ad libitum, until satiation. In study two, subjects ate a standardised amount of porridge, with mean bite size and mean eating rate covertly measured by observation through a one-way mirror. Both studies involved subjects completing a familiarisation visit and two experimental visits, where they ate with a teaspoon (SMALL) or dessert spoon (LARGE), in randomised order. Subjective appetite measures (hunger, fullness, desire to eat and satisfaction) were made before and after meals. In study one, subjects ate 8 % less food when they ate with the SMALL spoon (SMALL 532 (SD 189) g; LARGE 575 (SD 227) g; P=0·006). In study two, mean bite size (SMALL 10·5 (SD 1·3) g; LARGE 13·7 (SD 2·6) g; PSD 25) g/min; LARGE 108 (SD 29) g/min; Pad libitum food intake, possibly via a cascade of effects on within-meal eating microstructure. A small spoon might be a practical strategy for decreasing bite size and eating rate, likely increasing oral processing, and subsequently decreasing food intake, at least in lean young men.

Exercise facilitates weight control, partly through effects on appetite regulation. Single bouts of exercise induce a short-term energy deficit without stimulating compensatory effects on appetite, whilst limited evidence suggests that exercise training may modify subjective and homeostatic mediators of appetite in directions associated with enhanced meal-induced satiety. However, a large variability in responses exists between individuals. This article reviews the evidence relating to how adiposity, sex, and habitual physical activity modulate exercise-induced appetite, energy intake, and appetite-related hormone responses. The balance of evidence suggests that adiposity and sex do not modify appetite or energy intake responses to acute or chronic exercise interventions, but individuals with higher habitual physical activity levels may better adjust energy intake in response to energy balance perturbations. The effect of these individual characteristics and behaviours on appetite-related hormone responses to exercise remains equivocal. These findings support the continued promotion of exercise as a strategy for inducing short-term energy deficits irrespective of adiposity and sex, as well as the ability of exercise to positively influence energy balance over the longer term. Future well-controlled studies are required to further ascertain the potential mediators of appetite responses to exercise.

Whey protein is a commonly ingested nutritional supplement amongst athletes and regular exercisers, however, its role in post-exercise rehydration remains unclear. Eight healthy male and female participants completed two experimental trials involving the ingestion of 35 g of whey protein (WP) or maltodextrin (MD) at the onset of a rehydration period, followed by ingestion of water to a volume equivalent to 150% of the amount of body mass lost during exercise in the heat. The gastric emptying rates of the solutions were measured using 13C breath tests. Recovery was monitored for a further 3 h by the collection of blood and urine samples. The time taken to empty half of the initial solution (T1/2) was different between the trials (WP = 65.5 &plusmn, 11.4 min, MD = 56.7 &plusmn, 6.3 min, p = 0.05), however, there was no difference in cumulative urine volume throughout the recovery period (WP = 1306 &plusmn, 306 mL, MD = 1428 &plusmn, 443 mL, p = 0.314). Participants returned to net negative fluid balance 2 h after the recovery period with MD and 3 h with WP. The results of this study suggest that whey protein empties from the stomach at a slower rate than MD, however, this does not seem to exert any positive or negative effects on the maintenance of fluid balance in the post-exercise period.

Introduction: Breakfast omission may reduce daily energy intake. Exercising fasted impairs performance compared with exercising after breakfast, but the effect breakfast omission has on evening exercise performance is unknown. This study assessed the effect of omitting breakfast on evening exercise performance and within-day energy intake.\ud \ud Methods: Ten male, habitual breakfast eaters completed two trials in a randomized, counterbalanced order. Subjects arrived at the laboratory in an overnight-fasted state and either consumed or omitted a 733 ± 46 kcal (3095 ± 195 kJ) breakfast. Ad libitum energy intake was assessed at 4.5 h (lunch) and 11 h (dinner). At 9 h, subjects completed a 30-min cycling exercise at approximately 60% V˙O2peak, followed by a 30-min maximal cycling performance test. Food was not permitted for subjects once they left the laboratory after dinner until 0800 h the following morning. Acylated ghrelin, GLP-1(7–36), glucose, and insulin were assessed at 0, 4.5, and 9 h. Subjective appetite sensations were recorded throughout.\ud \ud Results: Energy intake was 199 ± 151 kcal greater at lunch (P < 0.01) after breakfast omission compared with that after breakfast consumption and tended to be greater at dinner after consuming breakfast (P = 0.052). Consequently, total ad libitum energy intake was similar between trials (P = 0.196), with 24-h energy intake 19% ± 5% greater after consuming breakfast (P < 0.001). Total work completed during the exercise performance test was 4.5% greater after breakfast (314 ± 53 vs 300 ± 56 kJ; P < 0.05). Insulin was greater during breakfast consumption at 4.5 h (P < 0.05), with no other interaction effect for hormone concentrations.\ud \ud Conclusions: Breakfast omission might be an effective means of reducing daily energy intake but may impair performance later that day, even after consuming lunch.

This study examined the effects of sodium chloride and potassium chloride supplementation during 48-h severe energy restriction on exercise capacity in the heat. Nine males completed three 48-h trials: adequate energy intake (100 % requirement), adequate electrolyte intake (CON); restricted energy intake (33 % requirement), adequate electrolyte intake (ER-E); and restricted energy intake (33 % requirement), restricted electrolyte intake (ER-P). At 48 h, cycling exercise capacity at 60 % $$ \dot{V} $$ O2 peak was determined in the heat (35.2 °C; 61.5 % relative humidity). Body mass loss during the 48 h was greater during ER-P [2.16 (0.36) kg] than ER-E [1.43 (0.47) kg; P

This study investigated the effects of hydration status and fluid availability on appetite and energy intake. Sixteen males completed four 24 h trials, visiting the laboratory overnight fasted on two consecutive days. Standardised foods were provided during the 24 h and on day two an ad-libitum semi-solid porridge breakfast was provided. Water intake during the 24 h (0 or 40 mL⋅kg(-1)) and fluid provision during the ad-libitum breakfast were manipulated so subjects were euhydrated with (EU-F) and without fluid (EU-NF) available at breakfast; and hypohydrated with (HYPO-F) and without fluid (HYPO-NF) available at breakfast. Blood samples (0 and 24 h), urine samples (0-24 h) and subjective responses (0, 24 and 24.5 h) were collected. HYPO trials decreased body mass by ~1.8%. Serum and urine osmolality increased and plasma volume decreased during HYPO trials (P 0.001). Total urine output was greater during EU than HYPO trials (P 0.001). Ad-libitum energy intake was not different between trials: 2658 (938) kJ (EU-F), 2353 (643) kJ (EU-NF), 2295 (529) kJ (HYPO-F), 2414 (954) kJ (HYPO-NF), (P = 0.131). Fluid intake was ~200 mL greater during HYPO-F than EU-F (P 0.01). There was an interaction effect for thirst (P 0.001), but not hunger or fullness. These results demonstrate that mild hypohydration produced by inadequate fluid intake and fluid availability during eating does not influence ad-libitum energy intake of a semi-solid breakfast, at least in healthy young males.

Angiotensin converting enzyme (ACE) and bradykinin receptor B2 (B2R) genetic variation may affect thirst because of effects on angiotensin II production and bradykinin activity, respectively. To examine this, 45 healthy Caucasian men completed 60 min of cycle exercise at 62% ± 5% peak oxygen uptake in a room heated to 30.5 ± 0.3 °C with ad libitum fluid intake. Blood samples were collected pre-, mid-, and immediately post-cycle. Fluid intake, body mass loss (BML), sweat loss (determined via changes in body mass and fluid intake), and thirst sensation were recorded. All participants were genotyped for the ACE insert fragment (I) and the B2R insert sequence (P). Participants were homozygous for the wild-type allele (WW or MM), heterozygous (WI or MP) or homozygous for the insert (II or PP). No differences between genotype groups were found in mean (±SD) voluntary fluid intake (WW: 613 ± 388, WI: 753 ± 385, II: 862 ± 421 mL, p = 0.31; MM: 599 ± 322, MP: 745 ± 374, PP: 870 ± 459 mL, p = 0.20), percentage BML or any other fluid balance variables for both the ACE and B2R genes, respectively. Mean thirst perception in the B2R PP group, however, was higher (p < 0.05) than both MM and MP at 30, 45, and 60 min. In conclusion, the results of this study suggest that voluntary fluid intake and fluid balance in healthy men performing 60 min of moderate-intensity exercise in the heat are not predominantly influenced by ACE or B2R genetic variation.

This study examined the effect of electrolyte addition to drinks ingested after severe fluid and energy restriction (FER). Twelve subjects (6 male and 6 female) completed 3 trials consisting of 24-hour FER (energy intake: 21 kJ·kg body mass; water intake: 5 ml·kg body mass), followed by a 2-hour rehydration period and a 4-hour monitoring period. During rehydration, subjects ingested a volume of drink equal to 125% of the body mass lost during FER in 6 aliquots, once every 20 minutes. Drinks were a sugar-free lemon squash (P) or the P drink with the addition of 50 mmol·L sodium chloride (Na) or 30 mmol·L potassium chloride (K). Total void urine samples were given before and after FER and every hour during rehydration and monitoring. Over all trials, FER produced a 2.1% reduction in body mass and negative sodium (-67 mmol), potassium (-48 mmol), and chloride (-84 mmol) balances. Urine output after drinking was 1627 (540) ml (P), 1391 (388) ml (K), and 1150 (438) ml (Na), with a greater postdrinking urine output during P than Na (p ≤ 0.05). Ingestion of drink Na resulted in a more positive sodium balance compared with P or K (p < 0.001), whereas ingestion of drink K resulted in a more positive potassium balance compared with P or Na (p < 0.001). These results demonstrate that after 24-hour FER, ingestion of a high sodium drink results in an increased sodium balance that augments greater drink retention compared with a low electrolyte placebo drink.