Search

Background: The daily energy imbalance gap associated with the current population weight gain in the obesity epidemic is relatively small. However, the substantially higher body weights of populations that have accumulated over several years are associated with a substantially higher total energy expenditure (TEE) and total energy intake (TEI), or energy flux (EnFlux = TEE = TEI). Objective: The objective was to develop an equation relating EnFlux to body weight in adults for estimating the rise in EnFlux associated with the obesity epidemic. Design: Multicenter, cross-sectional data for TEE from doubly labeled water studies in 1399 adults aged 5.9 [+ or -] 18.8 y (mean [+ or -] SD) were analyzed in linear regression models with natural log (In) weight as the dependent variable and In EnFlux as the independent variable, adjusted for height, age, and sex. These equations were compared with those for children and applied to population trends in weight gain. Results: In EnFlux was positively related to In weight ([beta] = 0.71; 95% CI: 0.66, 0.76; [R.sup.2] = 0.52), adjusted for height, age, and sex. This slope was significantly steeper than that previously described for children ([beta] = 0.45; 95% CI: 0.38, 0.51). Conclusions: This relation suggests that substantial increases in TEI have driven the increases in body weight over the past 3 decades. Adults have a higher proportional weight gain than children for the same proportional increase in energy intake, mostly because of a higher fat content of the weight being gained. The obesity epidemic will not be reversed without large reductions in energy intake, increases in physical activity, or both.

Background: Capsinoids from the Capsicum genus of plants are nonpungent capsaicin-related substances with effects on metabolism and body weight in animals. Objectives: Our objectives were to explore the safety and efficacy of capsinoids taken orally (6 mg/d) for weight loss, fat loss, and change in metabolism and to examine whether candidate genes are predictors of capsinoid response. Design: This was a 12-wk, placebo-controlled, double-blind, randomized study. Eligibility criteria included a body mass index (BMI; in kg/[m.sup.2]) of 25-35. Body weight was measured, and dual-energy X-ray absorptiometry, indirect calorimetry (men only), and genotyping were conducted. Results: Forty women and 40 men with a mean ([+ or -] SD) age of 42 [+ or -] 8 y and BMI of 30.4 [+ or -] 2.4 were randomly assigned to a capsinoid or placebo group. Capsinoids were well tolerated. Mean ([+ or -] SD) weight change was 0.9 [+ or -] 3.1 and 0.5 [+ or -] 2.4 kg in the capsinoid and placebo groups, respectively (P = 0.86). There was no significant group difference in total change in adiposity, but abdominal adiposity decreased more (P = 0.049) in the capsinoid group (-1.11 [+ or -] 1.83%) than in the placebo group (-0.18 [+ or -] 1.94%), and this change correlated with the change in body weight (r = 0.46, P < 0.0001). Changes in resting energy expenditure did not differ significantly between groups, but fat oxidation was higher at the end of the study in the capsinoid group (least-squares mean difference: 21.0 mg/min; P = 0.06). Of 13 genetic variants tested, TRPV1 Va1585Ile and UCP2 -866 G/A correlated significantly with change in abdominal adiposity. Conclusions: Treatment with 6 mg/d capsinoids orally appeared to be safe and was associated with abdominal fat loss. Capsinoid ingestion was associated with an increase in fat oxidation that was nearly significant. We identified 2 common genetic variants that may be predictors of therapeutic response.

Background: Twenty-four-hour dietary recalls have been used in large surveys of infant and toddler energy intake, but the accuracy of the method for young children is not well documented. Objective: We aimed to determine the accuracy of infant and toddler energy intakes by a single, telephone-administered, multiple-pass 24-h recall as compared with 3-d weighed food records. Design: A within-subjects design was used in which a 24-h recall and 3-d weighed food records were completed within 2 wk by 157 mothers (56 non-Hispanic white, 51 non-Hispanic black, and 50 Hispanic) of 7-11-mo-old infants or 12-24-mo-old toddlers. Child and caregiver anthropometrics, child eating patterns, and caregiver demographics and social desirability were evaluated as correlates of reporting bias. Results: Intakes based on 3-d weighed food records were within 5% of estimated energy requirements. Compared with the 3-d weighed food records, the 24-h recall overestimated energy intake by 13% among infants (740 [+ or -] 154 and 833 [+ or -] 255 kcal, respectively) and by 29% among toddlers (885 [+ or -] 197 and 1140 [+ or -] 299 kcal, respectively). Eating patterns (ie, frequency and location) did not differ appreciably between methods. Macronutrient and micronutrient intakes were higher by 24-h recall than by 3-d weighed food record. Dairy and grains contributed the most energy to the diet and accounted for 74% and 54% of the overestimation seen in infants and toddlers, respectively. Greater overestimation was associated with a greater number of food items reported by the caregiver and lower child weight-for-length z scores. Conclusions: The use of a single, telephone-administered, multiple-pass 24-h recall may significantly overestimate infant or toddler energy and nutrient intakes because of portion size estimation errors.

Glucosensing is a property of specialized neurons in the brain that regulate their membrane potential and firing rate as a function of ambient glucose levels. These neurons have several similarities to β- and α-cells in the pancreas, which are also responsive to ambient glucose levels. Many use glucokinase as a rate-limiting step in the production of ATP and its effects on membrane potential and ion channel function to sense glucose. Glucosensing neurons are organized in an interconnected distributed network throughout the brain that also receives afferent neural input from glucosensors in the liver, carotid body, and small intestines. In addition to glucose, glucosensing neurons can use other metabolic substrates, hormones, and peptides to regulate their firing rate. Consequently, the output of these 'metabolic sensing' neurons represents their integrated response to all of these simultaneous inputs. The efferents of these neurons regulate feeding, neuroendocrine and autonomic function, and thereby energy expenditure and storage. Thus, glucosensing neurons play a critical role in the regulation of energy homeostasis. Defects in the ability to sense glucose and regulatory hormones like leptin and insulin may underlie the predisposition of some individuals to develop diet-induced obesity., The term 'energy homeostasis' is a modification of the second law of thermodynamics whereby the amount of energy taken in as food equals the amount expended as heat (thermogenesis). When [...]

Study objectives: To characterize the metabolic status of weight-stable and clinically stable individuals with advanced emphysema. Patients: Seventy-nine patients with severe emphysema (FE[V.sub.1], 29 ± 13% of predicted [mean ± [...]

Background: Seasonality has been recognized as a key determinant of human energy balance, especially in low-income countries. Objective: The objective was to test the hypothesis that, in rural Bangladesh, different age and sex groups adapt similarly to seasonal changes in energy intake (EI). Design: A prospective study was carried out in 2 rural Bangladeshi villages in the lean and peak seasons. Data on anthropometric measures (weight, height, and midupper arm circumference) and dietary food intake (collected with the use of a 24-h food weighing method) were obtained from all subjects from 304 households. Results: The average EI increased from a least-squares mean ([+ or -] SE) of 7.87 [+ or -] 0.10 MJ * [person.sup.-1] * [d.sup.-1] in the lean season to 9.47 [+ or -] 0.13 MJ * [person.sup.-1] * [d.sup.-1] in the peak season. In children and adolescents aged < 18 y of age, the prevalence of underweight (weight-for-age) was not significantly different (56%) in the 2 seasons. Among adults, a significantly higher prevalence of chronic energy deficiency [body mass index (in kg/[m.sup.2] < 18.5] was observed in the peak season (67%) than in the lean season (61%), despite a higher EI in the peak season. Other determinants of seasonal nutritional status are presented. Conclusions: Seasonal fluctuations in EI were substantial in all age and sex groups. Children and adolescents showed no significant seasonal changes in the prevalence of underweight, which indicated that they adapted to changes in EI. In adults, the season in which EI was high coincided with average weight loss, which indicated that adults did not adapt fully to seasonal fluctuations in EI and that seasonal energy expenditure is probably a major determinant of nutritional status. KEY WORDS Seasonality, anthropometry, underweight, chronic energy deficiency, Bangladesh, children, adolescents, adults, physical activity level

IT'S NO WONDER YOU FEEL GROGGY AND SLUGGISH in the morning. You've just spent seven to nine hours barely moving. Muscles can tighten. Circulation and communication between nerves decreases. But […]

Background: Children have a high resting energy expenditure (REE) relative to their body weight. The decline in REE during growth may be due to changes in body composition or to changes in the metabolic rate of individual organs and tissues. Objectives: The goals were to quantify body-composition components in children at the organ-tissue level in vivo and to determine whether the observed masses 1) account for the elevated REE in children and 2) account, when combined with specific organ-tissue metabolic constants, for children's REE. Design: This was a cross-sectional evaluation of 15 children (aged 9.3 [+ or -] 1.7 y) and 13 young adults (aged 26.0 [+ or -] 1.8 y) with body mass indexes (in kg/[m.sup.2]) < 30. Magnetic resonance imaging-derived in vivo measures of brain, liver, kidney, heart, skeletal muscle, and adipose tissue were acquired. REE was measured by indirect calorimetry ([REE.sub.m]). Previously published organ-tissue metabolic rate constants were used to calculate whole-body REE ([REE.sub.c]). Results: The proportion of adipose-tissue-free mass as liver (3.7 [+ or -]0.5% compared with 3.1 [+ or -] 0.5%; P < 0.01) and brain (6.2 [+ or -] 1.2% compared with 3.3 [+ or -] 0.9%; P < 0.001) was significantly greater in children than in young adults. The addition of brain and liver mass significantly improved the model but did not eliminate the role of age. [REE.sub.c] with published metabolic coefficients underestimated [REE.sub.m] ([REE.sub.c] = 3869 [+ or -] 615 kJ/d; [REE.sub.m] = 5119 + 769 kJ/d; P < 0.001) in children. Conclusion: The decline in REE during growth is likely due to both a decrease in the proportion of some of the more metabolically active organs and tissues and changes in the metabolic rate of individual organs and tissues. KEY WORDS Organ mass, fat-free mass, resting energy expenditure, magnetic resonance imaging, growth, children

Background: Nicotine replacement therapy limits weight gain after smoking cessation. This finding is partly attributable to the thermogenic effect of nicotine, which may be enhanced by caffeine. Objective: We assessed the acute thermogenic effects of chewing gum containing different doses of nicotine and caffeine. Design: This randomized, double-blind, placebo-controlled, crossover study included 12 healthy, normal-weight men (aged 18-45 y). Energy expenditure was measured with indirect calorimetry before and 2.5 h after subjects chewed each of 7 different types of gum containing the following doses of nicotine/caffeine: 0/0, 1/0, 2/0, 1/50, 2/50, 1/100, and 2/100 mg/mg. Results: The thermogenic responses (increases over the response to placebo) were 3.7%, 4.9%, 7.9%, 6.3%, 8.5%, and 9.8%, respectively, for the gums containing 1/0, 2/0, 1/50, 2/50, 1/100, and 2/100 mg nicotine/mg caffeine (P < 0.05 for all). Adding caffeine to 1 and 2 mg nicotine significantly enhanced the thermogenic response, but changing the caffeine dose (from 50 to 100 mg) did not change the thermogenic effect. None of the combinations changed the respiratory quotient compared with placebo, which indicates that glucose and fat oxidation rates were increased to a similar extent. Side effects occurred only with 2 mg nicotine. Conclusions: One milligram of nicotine has a pronounced thermogenic effect, which can be increased by [approximately equal to] 100% by adding 100 mg caffeine. Increasing the nicotine dose to 2 mg does not increase the thermogenic effect but produces side effects in most subjects. Caffeine may be useful in preventing weight gain after smoking cessation if its thermogenic effect can be used to enhance nicotine's effect on long-term energy balance. KEY WORDS Nicotine, caffeine, fatty acid oxidation, carbohydrate oxidation, energy expenditure, respiratory quotient, smoking cessation, weight management, weight control, cigarette smoking

Background: Little is known about the effect of weight change on regional lean body mass (LBM) distribution or on racial differences in resting metabolic rate (RMR). Objective: The study compared total and regional LBM patterns in white and black women after weight loss and regain and assessed the influence of regional LBM on variances in RMR. Design: Eighteen white and 22 black women who did not differ in age, weight, and height were studied 3 times: in the overweight state, after weight reduction to the normal-weight state, and after 1 y without intervention. Total and regional lean and fat masses were assessed by dual-energy X-ray absorptiometry. Results: White and black women did not differ significantly in mean ([+ or -] SD) weight loss (13.4 [+ or -] 3.6 and 12.7 [+ or -] 3.2 kg, respectively) and regain (6.1 [+ or -] 5.5 and 6.4 [+ or -] 5.4 kg, respectively). Black subjects had significantly less trunk LBM and significantly more limb LBM at each time point (P < 0.05). In both races, weight regain was associated with significant increases in limb LBM (P < 0.05) but not in trunk LBM (P = 0.21). RMR, adjusted for total LBM and fat mass, was significantly higher in white women after weight loss (P < 0.01) and regain (P < 0.01). However, no racial difference was found when RMR was adjusted for LBM distribution. Conclusions: In both races, trunk LBM decreased with weight loss and remained lower, despite significant weight regain, which potentially reflected decreased organ mass. Regional LBM distribution explained the racial difference in RMR. KEY WORDS Overweight, obesity, weight loss, body composition, resting metabolic rate, lean body mass, fat mass, regional distribution, African American women

Background: The energy requirements of women have been based on total energy expenditure (TEE) derived from the factorial approach or as multiples of basal metabolic rate (BMR). Objective: This study was designed to reevaluate the energy requirements of healthy, moderately active underweight, normal-weight, and overweight women of reproductive age. Design: The energy requirements of 116 women [n = 13 with a low body mass index (BMI), n = 70 with a normal BMI, and n = 33 with a high BMI] were estimated from TEE measured by the doubly labeled water method. Twenty-four-hour EE and BMR were measured by room respiration calorimetry, activity EE was estimated from nonbasal EE as TEE - BMR, and physical activity level was calculated as TEE/BMR. Body composition was derived from a multicomponent model. Fitness, strength, and physical activity level were assessed, and fasting serum indexes were measured. Results: Energy requirements differed among the low-BMI (8.9 [+ or -] 0.9 MJ/d), normal-BMI (10.1 [+ or -] 1.4 MJ/d), and high-BMI (11.5 [+ or -] 1.9 MJ/d) groups (P = 0.02-0.001, all pairwise comparisons). Major predictors of BMR, 24-h EE, and TEE were weight, height, and body composition; minor predictors were fasting metabolic profile and fitness. Fat-free mass and fat mass accounted for the differences in EE seen between the BMI groups. The mean physical activity level of 1.86 suggested that the multiples of BMR used to estimate energy requirements have been underestimated. Conclusion: Recommended energy intakes for healthy, moderately active women of reproductive age living in industrialized societies should be revised on the basis of TEE. KEY WORDS Energy requirements, total energy expenditure, basal metabolic rate, activity, body composition, doubly labeled water method, women

Background: Estimating energy requirements is a frequent task in clinical studies. Objective: We examined weight patterns of participants enrolled in a clinical trial and evaluated factors that may affect weight stabilization. The Harris-Benedict equation and the FAO/WHO equation, used in conjunction with physical activity levels estimated with the 7-d Physical Activity Recall, were compared for estimating energy expenditure. Design: This was a multicenter, randomized controlled feeding trial with participants of the Dietary Approaches to Stop Hypertension Trial. For 11 wk, the amount of food participants received was adjusted to maintain their body weights as close to their initial weights as possible. Change-point regression techniques were used to identify weight-stable periods. Factors related to achieving weight stabilization were examined with logistic regression. Results: A stable weight was achieved by 86% of the 448 participants during the run-in period and by 78% during the intervention period. Energy intake averaged 11 [+ or -] 2.4 MJ/d (2628 [+ or -] 578 kcal/d), with most participants (n = 270) requiring 9-13 MJ/d (2100-3100 kcal/d). The difference between predicted and observed intakes was highest at high estimated energy intakes, mainly because of high and probably incorrect estimates of the activity factor. Participants with lower energy intakes tended to need less adjustment of their energy intakes to maintain a stable weight than did participants with higher energy intakes. Conclusions: Weight stabilization is not affected by diet composition, sex, race, age, or baseline weight. Either the Harris-Benedict equation or the FAO/WHO equation can be used to estimate energy needs. Activity factors > 1.7 often lead to overestimation of energy needs. KEY WORDS Harris-Benedict equation, FAO/WHO energy equation, stable weight, activity factor, controlled feeding study, clinical trial, clinical study

Background: Little is known about the relation between body composition and energy metabolism in paraplegia. Objective: We investigated the relation between body composition and energy metabolism in healthy paraplegics as compared with able-bodied control subjects. We hypothesized that paraplegics would have lower fat-free mass (FFM), body cell mass (BCM), resting metabolic rate (RMR), and thermic effect of feeding (TEF). Design: This cross-sectional study included 34 control subjects and 28 paraplegics (mean age: 29.1 [+ or -] 7.6 and 33.9 [+ or -] 9.2 y, respectively) with body mass indexes (in kg/[m.sup.2]) of 23.5 [+ or -] 1.8 and 24.3 [+ or -] 6.0, respectively. We measured RMR and TEF with indirect calorimetry, total body water with deuterium dilution, and extracellular water with corrected bromide space. We calculated FFM (total body water/0.732) and BCM [(total body water--extracellular water)/0.732)]. Results: FFM was higher in control subjects than in paraplegics (77.2 [+ or -] 7.2% and 69.2 [+ or -] 8.7%, respectively; P = 0.0002), as were BCM (47.4 [+ or -] 6.7% and 35.9 [+ or -] 8.1%, respectively; P < 0.0001) and RMR (7016 [+ or -] 935 and 6159 [+ or -] 954 kJ/d, respectively; P = 0.0007). FFM was the single best predictor of RMR in both groups ([r.sup.2] = 0.83 for control subjects and 0.70 for paraplegics, P < 0.0001 for both). RMR adjusted for FFM did not differ significantly between control subjects and paraplegics (6670 [+ or -] 504 and 6588 [+ or -] 501 kJ/d, respectively). TEF also did not differ significantly between control subjects and paraplegics (6.25 [+ or -] 2.2% and 5.53 [+ or -] 1.8% of energy intake, respectively). Conclusions: FFM, BCM, and RMR, but not obligatory TEF, are lower in paraplegics than in control subjects. RMR does not differ between control and paraplegic subjects after adjustment for FFM, indicating similar metabolic activity in the fat-free compartment of the body. KEY WORDS Paraplegia, disability, spinal cord injury, body composition, fat-free mass, resting metabolic rate, thermic effect of feeding

Background: High resistance training enhances muscular strength, and recent work has suggested an important role for metabolite accumulation in this process. Objective: To investigate the role of fatigue and metabolite [...]

This article investigates the relationship between aerobic fitness, muscle fiber composition, and oxygen cosumption levels among cyclists. An analysis of muscle lactate, energy metabolism, and gas exchange measurements is presented.

The relationship between energy deficits and body composition has been studied in 42 elite female gymnasts and runners. Findings indicate that within-day energy deficits are associated with higher body fat percentage in the anaerobic and aerobic athletes. Athletes would do well not to follow restrained or delayed eating patterns. The energy deficits are measured based frequency and/or magnitude of deficit.

How to keep your energy level as high as it was on the first day of your dive trip. It's not uncommon to feel so wiped out by the third [...]

Uncoupling protein (UCP) 3 and UCP2, mitochondrial carrier proteins dissipating electrochemical gradient across the mitochondrial inner membrane, have been implicated in the regulation of energy metabolism. The UCP3 gene is [...]

Background: On the basis of observations in rodents, leptin is thought to play a key role in the regulation of energy expenditure and food intake, but less is known of its influence on ingestive behavior and energy balance in humans. Objective: We examined the effect in women of a chronic energy deficit on plasma leptin concentrations and self-reported appetite and explored possible relations between leptin and appetite sensations. Design: Twelve healthy women (body mass index, in kg/[m.sup.2]: 23-37) participated in a metabolic ward study in which 3 wk of neutral energy balance was followed by 12 wk of energy deficit (energy intake reduced by 2 MJ/d and energy expenditure increased by 0.8 MJ/d). Body weight and composition were monitored, fasting leptin concentrations were measured 4 times, and feelings of hunger, fullness, desire to eat, and prospective consumption were monitored hourly throughout the day on 7 selected days. Results: Adiposity-adjusted leptin decreased by 54% after 1 wk of a moderate energy deficit and remained low after 6 and 12 wk. Leptin was associated with self-reported hunger, desire to eat, and prospective consumption (range of r: -0.6 to -0.7, P [is less than] 0.01). The greatest hunger increase coincided with the largest percentage drop in circulating leptin and the lowest final leptin concentration. The relation between leptin and hunger was not influenced by amount of weight or body fat loss. Conclusions: These findings support the idea that leptin is a physiologic regulator of hunger during energy deficits in humans; the role of leptin in the long-term regulation of food intake warrants further study. Am J Clin Nutr 1998;68:794-801.

Study objectives: A proportion of patients with chronic airflow limitation (CAL) have a raised resting energy expenditure (REE). The mechanism underlying this is not known. The question of whether the [...]

Recent research suggests that leptin may control body weight by regulating energy expenditure and energy intake in mice. To explore the possible role of leptin in the regulation of energy [...]

Leptin acts on the brain to inhibit feeding, increase thermogenesis, and decrease body weight. Neuropeptide Y (NPY)-ergic neurons of the hypothalamic arcuate nucleus (ARC) that project to the paraventricular nuclei [...]

For several years the concept of the 'fat burning zone' has rooted itself in the belief system of the general exercising public. Working within this 'zone' refers to maintaining an [...]