Search

This study aimed to examine the total energy expenditure (TEE) and physical activity level (PAL) of elite open-water swimmers. Our study group included 5 world-class competitive open-water swimmers. TEE was measured using the doubly labeled water method for 1 week. The TEE was 4549 ± 1185 kcal/day. The PAL was 3.22 ± 0.46. Our results may provide a reference to optimize energy requirement support.

Activity monitors such as the Actical accelerometer, the Sensewear armband, and the Intelligent Device for Energy Expenditure and Activity (IDEEA) are commonly validated against gold standards (e.g., doubly labeled water, or DLW) to determine whether they accurately measure total daily energy expenditure (TEE) or activity energy expenditure (AEE). However, little research has assessed whether these parameters or others (e.g., posture allocation) predict body weight change over time. The aims of this study were to (i) test whether estimated energy expenditure or posture allocation from the devices was associated with weight change during and following a low-calorie diet (LCD) and (ii) compare free-living TEE and AEE predictions from the devices against DLW before weight change. Eighty-seven participants from 2 clinical trials wore 2 of the 3 devices simultaneously for 1 week of a 2-week DLW period. Participants then completed an 8-week LCD and were weighed at the start and end of the LCD and 6 and 12 months after the LCD. More time spent walking at baseline, measured by the IDEEA, significantly predicted greater weight loss during the 8-week LCD. Measures of posture allocation demonstrated medium effect sizes in their relationships with weight change. Bland–Altman analyses indicated that the Sensewear and the IDEEA accurately estimated TEE, and the IDEEA accurately measured AEE. The results suggest that the ability of energy expenditure and posture allocation to predict weight change is limited, and the accuracy of TEE and AEE measurements varies across activity monitoring devices, with multi-sensor monitors demonstrating stronger validity.

The Husab Sand Lizard (Pedioplanis husabensis Berger-Dell’Mour and Mayer, 1989) is a recently described lacertid lizard endemic to a small region in the central Namib Desert. Although this species is of conservation concern, very little is known about how this lizard functions in its environment. We used the doubly labeled water method to measure the field energetics in this lizard species and we report on its foraging behavior. Pedioplanis husabensis had summer field metabolic rates (330 ± 140 J·d−1) that were similar to those of other similarly sized sit-and-wait foraging lizards (360 J·d−1), but only 43% that of an active foraging lizard of the same mass (770 J·d−1), despite using a movement-intensive, active foraging strategy. Additionally, the mean water influx rate (0.06 ± 0.03 mL·d−1) was 67% that of a desert reptile of the same size (0.09 mL·d−1). Active body temperatures were significantly lower in summer (34.3 ± 1.7 °C) than they were in autumn (36.8 ± 1.6 °C), and daily activity of lizards increased from 2.6 ± 0.9 h·d−1in summer to 4.3 ± 1.9 h·d−1in autumn. Relative to other species of actively foraging desert lizards, P. husabensis has lower energy requirements.

Exenatide is a medication similar in structure and effect to native glucagon-like peptide-1, an incretin hormone with glucose-lowering properties. The aim of the study was to measure the change in total energy expenditure (TEE) and body composition during exenatide administration and by deduction the relative contributions of energy expenditure and energy intake to exenatide-induced weight loss. Forty-five obese (body mass index, 30–40 kg·m–2) subjects were identified. After exclusion criteria application, 28 subjects entered into the study and 18 subjects (12 female, 6 male) completed the study, which consisted of 6 visits over 14 weeks and injection of exenatide for an average of 84 ± 5 days. Respiratory gas analysis and doubly labeled water measurements were performed before initiation of exenatide and after approximately 3 months of exenatide administration. The average weight loss from the beginning of injection period to the end of the study in completed subjects was 2.0 ± 2.8 kg (p = 0.01). Fat mass declined by 1.3 ± 1.8 kg (p = 0.01) while the fat-free mass trended downward but was not significant (0.8 ± 2.2 kg, p = 0.14). There was no change in weight-adjusted TEE (p = 0.20), resting metabolic rate (p = 0.51), or physical activity energy expenditure (p = 0.38) and no change in the unadjusted thermic effect of a meal (p = 0.37). The significant weight loss because of exenatide administration was thus the result of decreasing energy intake. In obese nondiabetic subjects, exenatide administration did not increase TEE and by deduction the significant weight loss and loss of fat mass was due to decreased energy intake.

The hypothesis that cold air temperatures (Ta) constrain the metabolic diversity of high-latitude endotherms is based on the observation among birds and mammals that mean field metabolic rate (FMR) increases, whereas the variability of FMR decreases, from the warm tropics to the cold poles. However, there is a paucity of FMR measurements from above 60° latitude and below 0 °C. We measured the daily energy expenditure of a high-latitude population of free-ranging snowshoe hares ( Lepus americanus Erxleben, 1777) in Yukon, Canada, in winter (Ta-mean = –16.4 °C) and in autumn (Ta-mean = 0.5 °C). Doubly labelled water measures of FMR were approximately 20% lower in winter than in autumn, and were a similar, low multiple of resting metabolic rate in both seasons (2.04 and 1.94, respectively). The mass-corrected FMR of snowshoe hares in winter was only half the value predicted by extrapolating the relationship between FMR and Ta > 0 to –16.4 °C. These results contribute to an emerging pattern of a reversal in the relationship between FMR and Ta in free-ranging mammals from negative above 0 °C to positive below 0 °C. We refer to the positive, low Ta portion of this relationship as the cold shoulder, and suggest that it may reflect the general necessity for free-ranging mammals to use behavioural and (or) physiological means to conserve energy during long winters when cold conditions coincide with resource scarcity.

To investigate whether circulating leptin levels are associated with energy expenditure in healthy humans, doubly labeled water energy measurements and food intake assessment were carried out in 27 women (mean age, 48.6 years; weight, 61.9 kg; body mass index, 23.2). Energy expenditure was determined over 13 days. Food intake was measured by 7-day food records. Leptin was measured by radioimmunoassay. Leptin level was strongly associated with percentage body fat (r = 0.59; p < 0.001), fat mass (r = 0.60; p < 0.001), and body mass index (r = 0.41; p = 0.03), but no correlation was observed with energy expenditure (r = 0.02; p = 0.93). After controlling for percentage body fat, a positive association of leptin level with energy expenditure of marginal significance (p = 0.06) was observed. There were no significant univariate associations of age, physical activity, lean body mass, height, or dietary variables with leptin level. When controlling for body fat, a significant positive correlation was observed for percent energy from carbohydrate and negative correlations with dietary fat and alcohol intake. These findings confirm previous associations between leptin and body fat content and suggest a relationship between serum leptin and energy expenditure level in healthy humans.Key words: leptin, energy expenditure, body composition, diet.

The body composition, milk consumption, and growth efficiency of Antarctic fur seal (Arctocephalus gazella) pups were measured over three consecutive lactation periods (1990–1992) at Bird Island, South Georgia. The body composition of pups differed between the sexes; whereas for any given age females were lighter than males, they had proportionately higher body lipid reserves than males. Milk consumption was determined on 388 occasions in 177 pups. Mean estimates of milk consumption ranged from 2.5 to 3.2 kg (42–53 MJ) during the 6-day perinatal period and from 2.9 to 3.6 kg (49–68 MJ) during the 1- to 2-day maternal attendance periods (feeding bouts). There were no differences in milk consumption between the sexes in any year. Both per-bout and per-day milk consumption increased steadily with age before decreasing significantly in the last 30–40 days of lactation. Per-bout milk consumption was positively related to the duration of the maternal foraging trip and attendance cycle, and both per-bout and per-day milk consumption were related to pup mass. Pups of both sexes consume the same amount of milk, but males direct more of their milk consumption into lean tissue growth than females, which accumulate greater adipose stores. Therefore, mass and mass changes may not be appropriate parameters for investigating differential maternal investment between the sexes in otariid pups.

We studied the daily energy expenditure of free-living nonreproductive carnivorous swift foxes (Vulpes velox, average mass 2.1 kg) on shortgrass prairie in southeastern Colorado in summer and winter in relation to air temperature, daily activity pattern, movement rate, and daily movement distance. The field metabolic rate (FMR) was measured with doubly labeled water, and activity and movements were monitored by radiotelemetry. During their nighttime activity period in winter, swift foxes traveled large distances (18.5 ± 0.6 km/d). Locomotion costs (estimated from daily movement distance in winter, using an allometric equation) accounted for at least 21% of total daily expenditure, the highest proportion reported for a mammal. During their nocturnal activity periods (winter vs. summer), swift foxes apparently traveled farther (ca. 13.0 vs. 5.7 km/night, using equal sampling intervals) and were active longer (ca. 12.9 vs. 11.3 h/night) in colder air. Nevertheless, FMR in winter (1488 kJ/d) was significantly lower than during summer (2079 kJ/d). We review available data for other free-living eutherians and show that low temperatures in winter are not necessarily associated with increases in FMR.

We examined the energy expenditure of adult male yellow-bellied marmots (Marmota flaviventris) and its relationship to various female-defense characteristics critical to male reproductive success. Resting metabolic rates of males were estimated in the laboratory via oxygen-consumption analysis, and field metabolic rates were estimated using a doubly labeled water technique. Male home-range size, number of females defended by males, dispersion of females in the habitat, and date into the active season were considered to be predictors of male energy expenditure in excess of maintenance costs (field metabolic rate minus resting metabolic rate). Energy expenditure was best explained by a defensibility index based on the number and dispersion of females defended; expenditure increased with number and dispersion of females. Energy expenditure increased with date into the active season. Environmental constraints on male activity during the mating season may have led to a shift in male reproductive investment to later in the season, when intruder pressure by conspecifics increased. No short-term survival costs were associated with high energy expenditure; males appeared to engage in reproductive behaviors congruent with their physiological capabilities.

We measured the field metabolic rate (FMR) of seven free-ranging and two captive blue grouse (Dendragapus obscurus) with doubly labeled water. Average carbon dioxide production (1.016 ± 0.088 L CO2∙kg−0.734∙h−1) of free-ranging grouse was 8% higher but not significantly different (P 2∙kg−0.734∙h−1). Ambient temperature was not correlated with FMR (P = 0.268). The mean fat content of free-ranging blue grouse was 39 g (3.4%), which was equal to the energy equivalent of about 3× daily standard metabolie rate (SMR). The FMR of free-ranging grouse averaged 657 ± 62 kJ/d or 1.6 × SMR. The FMRs of free-ranging blue grouse averaged about 25% below FMRs predicted from allometric equations; most were 35–40% below those predicted. We suggest that there is little energetic constraint on blue grouse during winter because they are able to maintain a positive energy balance by minimizing energy costs through effective thermoregulation, microhabitat selection, and reduced activity.

Growth rates, milk intake, activity patterns, and daily energy expenditures of neonatal caribou (Rangifer tarandus granti) and muskoxen (Ovibos moschatus) were compared over a 100-day period to examine the strategies of two arctic follower species with different life history patterns. Relative growth rates, which reflected milk protein and energy intake, were higher for caribou during the 1st week of age and after 75 days of age than for muskox calves. Daily energy expenditures, estimated with the doubly labeled water technique, were significantly greater for caribou neonates than for muskoxen. Adult female caribou lost body weight during the first 2–3 weeks of lactation, but then increased 15% above postpartum weights during the summer period. Adult female muskoxen maintained weight, with no significant changes throughout the summer. Caribou milk was higher in protein, dry matter, and energy content than that of muskoxen.