Use of [14C]-sodium bicarbonate/urea to measure total energy expenditure in overweight men and women before and after low calorie diet induced weight loss

The aim of this study was to evaluate the use of the [14C]-sodium bicarbonate/urea technique to measure the change in total energy expenditure after weight loss and a period of weight maintenance. Eleven healthy subjects (6 men and 5 women aged 50 +/- 3 yrs, BMI 34.1 +/-2.1 kg/ m2, body fat 38.7 +/-3%) underwent 8 weeks of energy restriction using a combination of "Modifast" formula and one small meal per day (approximately 3.3 MJ/day). For an additional 2 weeks, subjects resumed a solid food diet that contained enough energy to stabilize body weight at the newly reduced level. Body composition, total energy expenditure (TEE), resting energy expenditure (REE) and the thermic effect of a 2.7 MJ test meal (TEF) were measured at both weeks 0 and 10. At week 10 as compared to week 0, body weight decreased by 12.2+/-1.6 kg (12.5%)(P<0.001). Total fat and lean mass decreased by 8.4+/-1.0 kg (20.4%) and 3.8+/-0.7 kg (6.7%), respectively (P< 0.001). REE decreased by 500+/-128 kJ/day (5.6+/-1.3%)(P<0.002). Decreases in the TEE (0.18 +/-;3.7%)and TEF(1.4+/-0.9%) were not significant. In conclusion, although [14C]-sodium bicarbonate/urea was well tolerated and did not interfere with normal daily activities, it did not have sufficient sensitivity to accurately measure weight loss induced changes in TEE in the range of 0.1-10%.     

Energy balance in relation to cancer cachexia

The aim of the current study was to determine the contribution of increased resting energy expenditure (REE) and/or decreased energy intake (EI) to the development of weight loss in gastric and colorectal (GCR) and lung cancer patients. REE was measured in 22 GCR cancer patients and 17 lung cancer patients and was compared with REE values in 40 apparently healthy controls. REE in lung cancer patients expressed per kg fat free mass (REE/FFM) was significantly increased when compared to healthy controls (33.5 +/- 5.4 and 29.6 +/- 2.9 kcal, respectively; p < 0.01). GCR cancer patients had no elevated REE compared to these healthy controls. No significant differences in EI were established between the three groups. Eight GCR cancer patients reported a decrease in food intake compared to pre-disease intake, in contrast to only one lung cancer patient. Semi-starving GCR cancer patients showed a significant weight loss (8.7 +/- 8.1%), a low respiratory quoteint (RQ) (0.76 +/- 0.04) and a high beta-hydroxybutyrate level (259 +/- 192 mumol/l), but they showed no difference in REE compared to patients with a normal EI. The current study suggests that weight loss in GCR cancer patients is initiated by decreased food intake, whereas weight loss in lung cancer patients represents a combination of an increased REE and a relatively low EI.     

Peptide YY, appetite and food intake

Obesity is taking on pandemic proportions. The laws of thermodynamics, however, remain unchanged, as energy will be stored if less energy is expended than consumed; the storage is usually in the form of adipose tissue. Several neural, humeral and psychological factors control the complex process known as appetite. Recently, a close evolutionary relationship between the gut and brain has become apparent. The gut hormones regulate important gastrointestinal functions such as motility, secretion, absorption, provide feedback to the central nervous system on availability of nutrients and may play a part in regulating food intake. Peptide YY (PYY) is a thirty-six amino acid peptide related to neuropeptide Y (NPY) and is co-secreted with glucagon-like peptide 1. Produced by the intestinal L-cells, the highest tissue concentrations of PYY are found in distal segments of the gastrointestinal tract, although it is present throughout the gut. Following food intake PYY is released into the circulation. PYY concentrations are proportional to meal energy content and peak plasma levels appear postprandially after 1 h. PYY3-36 is a major form of PYY in both the gut mucosal endocrine cells and the circulation. Peripheral administration of PYY3-36 inhibits food intake for several hours in both rodents and man. The binding of PYY3-36 to the Y2 receptor leads to an inhibition of the NPY neurones and a possible reciprocal stimulation of the pro-opiomelanocortin neurones. Thus, PYY3-36 appears to control food intake by providing a powerful feedback on the hypothalamic circuits. The effect on food intake has been demonstrated at physiological concentrations and, therefore, PYY3-36 may be important in the everyday regulation of food intake.     

Energy metabolic profile of mice after chronic activation of central NPY Y1, Y2, or Y5 receptors

OBJECTIVE: Neuropeptide Y (NPY), a 36-amino acid peptide with orexigenic properties, is expressed abundantly in the central nervous system and binds to several NPY receptor subtypes. This study examines the roles of the NPY Y1, Y2, and Y5 receptor(s) in energy homeostasis. RESEARCH METHODS AND PROCEDURES: We administered intracerebroventricular NPY (3 microg/d) or selective peptide agonists for the Y1, Y2, and Y5 receptor subtypes to C57Bl/6 mice for 6 days by mini-osmotic pumps to assess the role of each receptor subtype in NPY-induced obesity. Energy expenditure (EE) and respiratory quotient (RQ) were studied using indirect calorimetry. Adiposity was measured by DXA scanning and fat pad dissection. Insulin sensitivity was tested by whole-blood glucose measurement after an insulin challenge. RESULTS: Central administration of the selective Y1 agonist, Y5 agonist, or NPY for 6 days in mice significantly increased body weight, adiposity, and RQ, with significant hyperphagia in the Y5 agonist- and NPY-treated groups but not in the Y1 agonist-treated group. The NPY, Y1, or Y5 agonist-treated mice had little change in total EE during ad libitum and pair-feeding conditions. Conversely, selective activation of the Y2 receptor reduced feeding and resulted in a significant, but transient, weight loss. DISCUSSION: Central activation of both Y1 and Y5 receptors increases RQ and adiposity, whereas only Y5 receptor activation reduces energy expended per energy ingested. Selective activation of Y2 autoreceptors leads to hypophagia and transient weight loss, with little effect on total EE. Our study indicates that all three NPY receptor subtypes may play a role in regulating energy homeostasis in mice.     

Carbohydrate-restricted diets high in either monounsaturated fat or protein are equally effective at promoting fat loss and improving blood lipids

BACKGROUND: When substituted for carbohydrate in an energy-reduced diet, dietary protein enhances fat loss in women. It is unknown whether the effect is due to increased protein or reduced carbohydrate. OBJECTIVE: We compared the effects of 2 isocaloric diets that differed in protein and fat content on weight loss, lipids, appetite regulation, and energy expenditure after test meals. DESIGN: This was a parallel, randomized study in which subjects received either a low-fat, high-protein (LF-HP) diet (29 +/- 1% fat, 34 +/- 0.8% protein) or a high-fat, standard-protein (HF-SP) diet (45 +/- 0.6% fat, 18 +/- 0.3% protein) during 12 wk of energy restriction (6 +/- 0.1 MJ/d) and 4 wk of energy balance (7.4 +/- 0.3 MJ/d). Fifty-seven overweight and obese [mean body mass index (in kg/m(2)): 33.8 +/- 0.9] volunteers with insulin concentrations >12 mU/L completed the study. RESULTS: Weight loss (LF-HP group, 9.7 +/- 1.1 kg; HF-SP group, 10.2 +/- 1.4 kg; P = 0.78) and fat loss were not significantly different between diet groups even though the subjects desired less to eat after the LF-HP meal (P = 0.02). The decrease in resting energy expenditure was not significantly different between diet groups (LF-HP, -342 +/- 185 kJ/d; HF-SP, -349 +/- 220 kJ/d). The decrease in the thermic effect of feeding with weight loss was smaller in the LF-HP group than in the HF-SP group (-0.3 +/- 1.0% compared with -3.6 +/- 0.7%; P = 0.014). Glucose and insulin responses to test meals improved after weight loss (P < 0.001) with no significant diet effect. Bone turnover, inflammation, and calcium excretion did not change significantly. CONCLUSION: The magnitude of weight loss and the improvements in insulin resistance and cardiovascular disease risk factors did not differ significantly between the 2 diets, and neither diet had any detrimental effects on bone turnover or renal function.     

Increased dietary protein modifies glucose and insulin homeostasis in adult women during weight loss

Amino acids interact with glucose metabolism both as carbon substrates and by recycling glucose carbon via alanine and glutamine; however, the effect of protein intake on glucose homeostasis during weight loss remains unknown. This study tests the hypothesis that a moderate increase in dietary protein with a corresponding reduction of carbohydrates (CHO) stabilizes fasting and postprandial blood glucose and insulin during weight loss. Adult women (n = 24; >15% above ideal body weight) were assigned to either a Protein Group [protein: 1.6 g/(kg. d); CHO <40% of energy] or CHO Group [protein: 0.8 g/(kg. d); CHO >55%]. Diets were equal in energy (7100 kJ/d) and fat (50 g/d). After 10 wk, the Protein Group lost 7.53 +/- 1.44 kg and the CHO Group lost 6.96 +/- 1.36 kg. Plasma amino acids, glucose and insulin were determined after a 12-h fast and 2 h after a 1.67 MJ test meal containing either 39 g CHO, 33 g protein and 13 g fat (Protein Group) or 57 g CHO, 12 g protein and 14 g fat (CHO Group). After 10 wk, subjects in the CHO Group had lower fasting (4.34 +/- 0.10 vs 4.89 +/- 0.11 mmol/L) and postprandial blood glucose (3.77 +/- 0.14 vs. 4.33 +/- 0.15 mmol/L) and an elevated insulin response to meals (207 +/- 21 vs. 75 +/- 18 pmol/L). This study demonstrates that consumption of a diet with increased protein and a reduced CHO/protein ratio stabilizes blood glucose during nonabsorptive periods and reduces the postprandial insulin response.     

Ornithine restores ureagenesis capacity and mitigates hyperammonemia in Otc(spf-ash) mice

We showed that Otc(spf-ash) mice, a model of ornithine transcarbamylase deficiency, were able to sustain ureagenesis at the same rate as control mice, despite reduced enzyme activity, when a complete mixture of amino acids was provided. An unbalanced amino acid mixture, however, resulted in reduced ureagenesis and hyperammonemia. To study the effect of ornithine supplementation [316 micromol/(kg.h)] on urea and glutamine kinetics in conscious Otc(spf-ash) mice under a glycine-alanine load [6.06 mmol/(kg.h)], a multiple tracer infusion protocol ([(13)C(18)O]urea, [5-(15)N]glutamine, [2,3,3,4,4 D(5)]glutamine and [ring-D(5)] phenylalanine) was conducted. Ornithine supplementation increased ureagenesis [3.18 +/- 0.88 vs. 4.56 +/- 0.51 mmol/(kg.h), P < 0.001], reduced plasma ammonia concentration (1125 +/- 621 vs. 193 +/- 94 micromol/L, P < 0.001), and prevented acute hepatic enlargement (P < 0.006) in Otc(spf-ash) mice. Ornithine supplementation also increased [96 +/- 20 vs. 120 +/- 16 micromol/(kg.h), P < 0.001] the transfer of (15)N from glutamine to urea, to values observed in the control mice [123 +/- 17 micromol/(kg.h)]. De novo amido-N glutamine flux was higher [1.57 +/- 0.37 vs. 3.04 +/- 0.86 mmol/(kg.h); P < 0.001] in Otc(spf-ash) mice, but ornithine supplementation had no effect (P < 0.56). The flux of glutamine carbon skeleton was affected by both genotype (P < 0.0001) and by ornithine (P 0. 036). In conclusion, ornithine supplementation restored ureagenesis, mitigated hyperammonemia, prevented liver enlargement, and normalized the transfer of (15)N from glutamine to urea. These data strongly suggest that ornithine has the potential for the biochemical correction of OTCD in Otc(spf-ash) mice.     

Resting energy expenditure in reduced-obese subjects in the National Weight Control Registry.

BACKGROUND: Weight loss in obese subjects is associated with a reduction in resting metabolic rate (RMR). Whether the reduction can be explained solely by a reduction in lean body mass remains controversial. OBJECTIVE: Our objective was to determine whether the reduction in RMR after weight loss was proportional to the decrease in lean mass alone or was greater than could be explained by body composition. DESIGN: We measured the RMR, fasting respiratory quotient (RQ), and body composition in 40 reduced-obese subjects [ie, 7 men and 33 women who had lost > or = 13.6 kg (30 lb) and maintained the loss for > or = 1 y] enrolled in the National Weight Control Registry and 46 weight-matched control subjects (9 men, 37 women). RESULTS: A stepwise multiple regression found lean mass, fat mass, age, and sex to be the best predictors of RMR in both groups. After adjusting RMR for these variables, we found no significant difference in RMR (5926 +/- 106 and 6015 +/- 104 kJ/d) between the 2 groups (P = 0.35). When we adjusted fasting RQ for percentage body fat and age, the reduced-obese group had a slightly higher (0.807 +/- 0.006) RQ than the control group (0.791 +/- 0.005, P = 0.05). This may have been due to the consumption of a diet lower in fat or to a reduced capacity for fat oxidation in the reduced-obese group. CONCLUSION: These results show that in at least some reduced-obese individuals there does not seem to be a permanent obligatory reduction in RMR beyond the expected reduction for a reduced lean mass.     

Regulation of peptide YY levels by age, hormonal, and nutritional status

OBJECTIVE: Peptide YY (PYY) 3-36 has recently been recognized as an important gut hormone that influences food intake. Peripheral injections of PYY 3-36 in rats inhibit food intake in experimental animals as well as in lean and obese human subjects. This hormone has been suggested as an attractive therapeutic option for obesity. The aim of this study was to assess the influence of age, sex, thyroid status, growth hormone (GH), pregnancy, and food restriction on PYY levels in rat. RESEARCH METHODS AND PROCEDURES: We determined plasma PYY levels in all experimental sets. RESULTS: PYY levels were influenced by age, with the highest hormone levels achieved in early postnatal life (day 10) and decreasing thereafter. PYY levels were also dependent on thyroid hormone status being decreased in hyperthyroid rats. Exogenous GH administration led to a clear-cut decrease in PYY levels in both normal and GH-deficient rats. Acute food deprivation or chronic food restriction led to decreased PYY levels in virgin and pregnant rats. In pregnant rats with food available ad libitum, PYY levels were enhanced at late gestation. DISCUSSION: Our observations indicate that PYY levels are influenced by age, thyroid hormones, and GH. These data indicate that PYY could be involved in the changes of food intake associated with these conditions. The PYY levels observed in acute and chronic food-restricted rats indicate that, in situations of decreased energy intake, the lower PYY levels could serve to disinhibit central pathways and facilitate food intake.     

Regulation of sulfur amino acid metabolism in men in response to changes in sulfur amino acid intakes

We showed previously that 64% of the total dietary sulfur amino acid (SAA) requirement could be supported by dietary cysteine (Cys). However, the observation of such a sparing effect may be affected by the dietary intakes of SAA provided. The aim of this study was to compare methionine (Met) metabolism and transsulfuration (TS) in five healthy men fed three different diets (in random order) for 3 d each, with varying combinations of Met and Cys: 24 mg Met/(kg. d) and no Cys (diet A); 13 mg Met/(kg. d) and 11 mg Cys/(kg. d) (diet B); and 5 mg Met/(kg. d) and 19 mg Cys/(kg. d) (diet C). On d 3, Met kinetics and TS were assessed using orally administered L-[1-(13)C, methyl-(2)H(3)]methionine. Met demethylation (transmethylation, TM) significantly decreased as the dietary Met to Cys ratio decreased. Met TS was significantly lower during diets B [2.8 +/- 0.4 micro mol/(kg. h)] and C [1.5 +/- 0.5 micro mol/(kg. h)] than during diet A [7.8 +/- 2.9 micro mol/(kg. h)] (P < 0.05). The results of the present study indicate that when the ratio of Met to Cys fed is typical of that found in major food proteins and total SAA are sufficient to meet requirements, TS is significantly reduced compared with the case in which SAA needs are supplied by Met alone. We conclude that Cys sparing occurs through an increase in the fraction of the homocysteine pool destined for RM relative to TS (RM:TS).     

Energy intake and energy expenditure: a controlled study comparing dietitians and non-dietitians

BACKGROUND: Underreporting of food intake has been commonly observed. We hypothesized that experience with recording dietary information might increase the accuracy of the records. To test this hypothesis, we compared energy intake and energy expenditure in dietitians-who are experienced in recording food intake-with those of non-dietitians, whose only exposure to training to record food was in the context of this trial. SUBJECTS/SETTING: Subjects for this study were 10 female registered dietitians and 10 women of comparable age and weight who were not dietitians. DESIGN: This study compared the energy intake obtained from 7-day food records with energy expenditure measured over the corresponding 7-day period using doubly labeled water. STATISTICAL ANALYSIS: Data were compared by an analysis of variance METHODS: All subjects were trained to provide a 7-day weighed food intake record. Energy expenditure was measured with doubly labeled water over the 7 days when the weighed food intake record was obtained. A total of 10 dietitians and a control of group of 10 women of similar age and weight were recruited for this study. Participants were told that the goal was to record food intake as accurately as possible, because it would be compared with the simultaneous measurement of energy expenditure determined by doubly labeled water. RESULTS: The energy expenditure of the dietitians and controls were not different (2,154+/-105 [mean+/- standard error of the mean] kcal/day for dietitians and 2,315 +/- 90 kcal/ day for controls). The dietitians underreported their energy intake obtained from the food records by an average of 223 +/- 116 kcal/day, which was not different from their energy expenditure. Participants in the control group, as hypothesized, significantly underreported their energy intake (429 +/- 142 kcal/day, P < .05). CONCLUSION: Dietitians estimated their energy intake more accurately than non-dietitians, suggesting that familiarity with and interest in keeping food records may lead to more reliable estimates of energy intake.     

Energy metabolism in African Americans: potential risk factors for obesity.

BACKGROUND: Recent reports have identified a lower resting metabolic rate in African Americans than in whites, but most studies included only females and used short-term measurements with ventilated-hood systems. OBJECTIVE: Our objective was to compare 24-h measurements of energy metabolism between African American and white women and men using a respiratory chamber. DESIGN: Thirty-eight African American (x +/- SD: 32 +/- 7 y of age, 24 +/- 10% body fat) and 288 white (31 +/- 7 y of age, 26 +/- 12% body fat) subjects spent 24 h in a respiratory chamber for measurement of 24-h energy expenditure (24EE), sleeping metabolic rate (SMR), 24-h respiratory quotient (24RQ), and substrate oxidation rates. RESULTS: After adjustment for sex, age, and body composition (by hydrodensitometry), African Americans had lower SMR (-301 +/- 105 kJ/d; P < 0.01) and higher 24RQ (0.014 +/- 0.004; P < 0.001) than whites, whereas 24EE was similar. A sex-specific analysis, using a subset of 38 whites with an equal sex distribution and similar age and body weight, revealed that African American women had lower SMR (-442 +/- 182 kJ/d; P < 0.05) and lower 24EE (-580 +/- 232 kJ/d; P < 0.05), but similar 24RQ values compared with white women. African American men tended to have lower SMRs than white men (-355 +/- 188 kJ/d; P = 0. 07), but had higher 24RQ values, accounting for a 992 +/- 327-kJ/d lower 24-h fat oxidation rate (P < 0.005). CONCLUSIONS: These data not only confirm the findings of a lower metabolic rate in African American than in white women, but also suggest that fat oxidation is lower in African American men than in white men.     

Aerobic exercise training decreases leucine oxidation at rest in healthy adults

Both exercise and dietary protein intake affect whole-body protein turnover (WBPTO). Few studies have investigated the effect of aerobic exercise training on WBPTO [leucine rate of appearance (Ra), oxidation (Ox), and nonoxidative leucine disposal (NOLD)] in untrained individuals consuming a specified level of protein. This study examined the effect of aerobic exercise training on WBPTO in untrained men and women during a controlled diet intervention providing 0.88 g protein/(kg . d). After a 2-wk adaptation to the study diet, 7 subjects [3 men, 4 women; 76.1 +/- 5.8 kg, 164.7 +/- 4.4 cm, 30.7 +/- 4.5% body fat, 39.1 +/- 2.8 VO(2max) (maximal oxygen uptake) mL/(kg . min)] participated in 4 wk of aerobic exercise training (running and walking 4-5 times/wk at 65-85% maximal heart rate). WBPTO (determined via constant infusion of 1-[(13)C] leucine), nitrogen balance, and body composition were determined at baseline and after 4 wk of training. Nitrogen balance (-1.0 +/- 0.7 vs. 0.9 +/- 1.1 g N/24 h, P = 0.03) improved with exercise training, whereas body mass and composition did not change. Leucine Ra did not change, Ox decreased [18 +/- 2 to 15 +/- 2 micromol/(kg . h), P 相似文献   

The decrease in body fat in mice fed conjugated linoleic acid is due to increases in energy expenditure and energy loss in the excreta

We carried out energy balance studies in four groups of young, growing, 5-wk-old Balb-C mice (n = 12/group) that were either food restricted or nonrestricted and fed high fat diets (38 energy%) with or without 0.93 g/100 g conjugated linoleic acid (CLA) for 39 d. The energy in carcasses, excreta and food was measured in a bomb calorimeter. CLA lowered the percentage of the energy intake that was stored in the body from 1.9 +/- 0.8 to -2.3 +/- 0.7% (mean +/- SD, P < 0.05) in the nonrestricted mice and from 1.4 +/- 1.3 to -2.9 +/- 0.7% (P < 0.05) in the restricted mice. Thus, the CLA-treated mice had a net loss of body energy. The percentage of the energy intake eliminated in the excreta increased from 7.6 +/- 0.9% in controls to 8.7 +/- 1.0% (P < 0.05) in the CLA-treated mice that were nonrestricted and from 7.3 +/- 0.8 to 8.4 +/- 0.6 (P < 0.05) in the restricted mice. The amount of energy ingested minus the amount retained in carcasses and excreta equals the energy expenditure. The percentage of the energy intake that was expended as heat increased from 90.5 +/- 1.2 in controls to 93.6 +/- 1.5% (P < 0.05) in the CLA-treated nonrestricted mice and from 91.3 +/- 1.5 to 94.5 +/- 1.0% (P < 0.05) in the restricted mice. The lower energy storage in the CLA-fed mice was accounted for by an increase in the energy expenditure (74%) and by an increase in energy lost in the excreta (26%). Feeding CLA also increased liver weight, which may warrant further studies on the safety of CLA.     

Short-term growth and substrate use in very-low-birth-weight infants fed formulas with different energy contents

BACKGROUND: Currently available preterm formulas with energy contents of 3350 kJ (800 kcal)/L promote weight and length gain at rates at or above intrauterine growth rates but disproportionately increase total body fat. OBJECTIVE: The objective of this study was to determine whether fat accretion in formula-fed, very-low-birth-weight (VLBW) infants could be decreased and net protein gain maintained by reducing energy intakes from 502 kJ (80 kcal)*kg(-)(1)*d(-)(1) [normal-energy (NE) formula] to 419 kJ (100 kcal)*kg(-)(1)*d(-)(1) [low-energy (LE) formula] while providing similar protein intakes (3.3 g*kg(-)(1)*d(-)(1)). DESIGN: The study was a randomized, controlled trial enrolling 20 appropriate-for-gestational-age (AGA) and 16 small-for-gestational-age (SGA) VLBW infants (mean birth weight: 1.1 kg; mean gestational age: 31 wk); energy expenditure and nutrient balance were measured at 4 wk of age and anthropometric measurements were made when infants weighed 2 kg. RESULTS: The percentage of fat in newly formed tissue was significantly lower in AGA infants fed the LE formula (n = 9) than in those fed the NE formula (n = 10) (9% compared with 23%; analysis of variance, P = 0.001). Energy expenditure was higher in AGA infants fed the NE formula than in those fed the LE formula. Skinfold thickness was markedly lower in AGA infants fed the LE formula than in those fed the NE formula, resulting in a lower estimated percentage body fat (8.0 +/- 1.9% and 10.8 +/- 3.5%, respectively; P < 0.05). Three of 6 SGA infants fed the LE formula were excluded during the study because of poor weight gain. CONCLUSIONS: Body composition can easily be altered by changing the energy intakes of formula-fed VLBW infants. Energy intakes in these infants should be >419 kJ (100 kcal)*kg(-)(1)*d(-)(1).     

Postabsorptive respiratory quotient and food quotient-an analysis in lean and obese men and women

OBJECTIVE: Macronutrient intake is difficult to measure under free-living conditions, because of errors in the reporting of food intake. The aim of the current study was to assess whether postabsorptive respiratory quotient (RQ) is indicative for the food quotient (FQ), with other factors, such as body composition and energy balance, taken into account. SUBJECTS: Thirty lean subjects (age 31+/-9 y, body mass index (BMI) 22.0+/-2.1 kg/m2) and 20 obese subjects (age 48+/-12 y, BMI 33.3+/-4.4 kg/m2) participated in the study. DESIGN: Body mass changes were determined over a 7 day period before the measurement of postabsorptive RQ and in this period subjects reported their total food intake in a dietary record. A subgroup of 12 lean subjects was supplied with their total food intake in this period (twice with different diets). Food quotients were calculated from the valid food records (<10% underrecording and undereating). Body composition was estimated using the three-compartment model of Siri. RESULTS: Postabsorptive RQ was not related to FQ (n=31, r=-0.24, P=0.2) and no difference was observed between the two diet periods (n=12 paired t-test, P=0.9). Postabsorptive RQ was related to the change in body mass (r=0.57, P=0.0001), but not to BMI, fat mass or fat-free mass. CONCLUSIONS: In the present study, the energy balance over the days prior to the measurement was the most important factor influencing postabsorptive RQ. Postabsorptive RQ was not a reliable indicator for habitual FQ even when corrected for energy balance and body composition.     

Energy intake and physical activity in Pima Indians: comparison with energy expenditure measured by doubly-labeled water

To test the validity of survey techniques for measuring diet and activity patterns of Pima Indians, sequential 24-hour recalls, a food frequency questionnaire (FFQ), and an activity questionnaire were compared to free-living energy expenditure. Total energy expenditure (TEE) measured by doubly labeled water was 13.27 +/- 2.95 MJ/d for the 12 males (mean +/- SD: 35 +/- 14 yr; 97 +/- 35 kg; 32 +/- 9% body fat) and 11.67 +/- 1.85 MJ/d for the 9 females (31 +/- 13 yr; 106 +/- 32 kg; 49 +/- 6% body fat). Energy intake assessed by 24-hour recall was 13.59 +/- 7.81 MJ/d for men and 9.29 +/- 2.77 MJ/d for women, compared to 12.84 + 2.85 and 9.40 + 2.61 MJ/d for men and women, respectively, by FFQ. Both dietary methods indicated significant underreporting by women when compared to TEE. Energy intake assessed by FFQ was significantly correlated with TEE (r=0.48, p=0.03). This was true with 24-hour recall energy intake only when data from two extremely large alcohol consumers were eliminated (r=0.64, p=0.03, N=19). Although a low level of activity was apparent, the activity questionnaire produced significant correlations with measurements of energy expenditure and therefore represents an important tool for examining the relationship between physical activity and diseases.     

Why are nutritionally stunted children at increased risk of obesity? Studies of metabolic rate and fat oxidation in shantytown children from São Paulo, Brazil

BACKGROUND: Previous research suggested that nutritionally stunted children may have increased risk of obesity, but little is known about potential underlying mechanisms. OBJECTIVE: We sought to test the hypothesis that stunted children have a low metabolic rate and impaired fat oxidation relative to nonstunted children. DESIGN: The subjects were 58 prepubertal boys and girls aged 8-11 y from the shantytowns of S?o Paulo, Brazil. Twenty-eight were stunted (height-for-age z score <-1.5) and 30 had similar weight-for-height but normal height (height-for-age z score >-1.5). Parents of children in the 2 groups had equivalent height and body mass index values. Fasting and postprandial energy expenditure, respiratory quotient (RQ), and substrate oxidation were measured with indirect calorimetry in a 3-d resident study in which all food was provided and body composition was measured with dual-energy X-ray absorptiometry. RESULTS: Stunted children had normal resting energy expenditure relative to body composition compared with control children (4559 +/- 90 and 4755 +/- 86 kJ/d, respectively; P: = 0.14) and had normal postprandial thermogenesis (2.4 +/- 0.3% and 2.0 +/- 0.3% of meal load, respectively; P: = 0.42). However, fasting RQ was significantly higher in the stunted group (0.92 +/- 0.009 compared with 0.89 +/- 0.007; P: = 0.04) and consequently, fasting fat oxidation was significantly lower (25 +/- 2% compared with 34 +/- 2% of energy expenditure; P: < 0.01). CONCLUSIONS: Childhood nutritional stunting is associated with impaired fat oxidation, a factor that predicted obesity in other at-risk populations. This finding may help explain recent increases in body fatness and the prevalence of obesity among stunted adults and adolescents in developing countries.     

Low plasma leptin concentration and low rates of fat oxidation in weight-stable post-obese subjects

OBJECTIVE: A low resting metabolic rate for a given body size and composition, a low rate of fat oxidation, low levels of physical activity, and low plasma leptin concentrations are all risk factors for body weight gain. The aim of the present investigation was to compare resting metabolic rate (RMR), respiratory quotient (RQ), levels of physical activity, and plasma leptin concentrations in eight post-obese adults (2 males and 6 females; 48.9 +/- 12.2 years; body mass index [BMI]: 24.5 +/- 1.0 kg/m2; body fat 33 +/- 5%; mean +/- SD) who lost 27.1 +/- 21.3 kg (16 to 79 kg) and had maintained this weight loss for > or =2 months (2 to 9 months) to eight age- and BMI-matched control never-obese subjects (1 male and 7 females; 49.1 +/- 5.2 years; BMI 24.4 +/- 1.0 kg/m2; body fat 33 +/- 7%). RESEARCH METHODS AND PROCEDURES: Following 3 days of weight maintenance diet (50% carbohydrate and 30% fat), RMR and RQ were measured after a 10-hour fast using indirect calorimetry and plasma leptin concentrations were measured using radioimmunoassay. Levels of physical activity were estimated using an accelerometer over a 48-hour period in free living conditions. RESULTS: After adjustment for fat mass and fat-free mass, post-obese subjects had, compared with controls, similar levels of physical activity (4185 +/- 205 vs. 4295 +/- 204 counts) and similar RMR (1383 +/- 268 vs. 1430 +/- 104 kcal/day) but higher RQ (0.86 +/- 0.04 vs. 0.81 +/- 0.03, p < 0.05). Leptin concentration correlated positively with percent body fat (r = 0.57, p < 0.05) and, after adjusting for fat mass and fat-free mass, was lower in post-obese than in control subjects (4.5 +/- 2.1 vs. 11.6 +/- 7.9 ng/mL, p < 0.05). DISCUSSION: The low fat oxidation and low plasma leptin concentrations observed in post-obese individuals may, in part, explain their propensity to relapse.     

Physiologic growth hormone replacement improves fasting lipid kinetics in patients with HIV lipodystrophy syndrome

BACKGROUND: HIV lipodystrophy syndrome (HLS) is characterized by accelerated lipolysis, inadequate fat oxidation, increased hepatic reesterification, and a high frequency of growth hormone deficiency (GHD). The effect of growth hormone (GH) replacement on these lipid kinetic abnormalities is unknown. OBJECTIVE: We aimed to measure the effects of physiologic GH replacement on lipid kinetics in men with HLS and GHD. DESIGN: Seven men with HLS and GHD were studied with the use of infusions of [13C1]palmitate, [2H5]glycerol, and [2H3]leucine to quantify total and net lipolysis, palmitate and free fatty acid (FFA) oxidation, and VLDL apolipoprotein B-100 synthesis before and after 6 mo of GH replacement (maximum: 5 microg x kg(-1) x d(-1)). RESULTS: GH replacement decreased the rates of total lipolysis [FFA(total) rate of appearance (x +/- SE): from 4.80 +/- 1.24 to 3.32 +/- 0.76 mmol FFA x kg fat(-1) x h(-1); P < 0.05] and net lipolysis (FFA(net) rate of appearance: from 1.87 +/- 0.34 to 1.20 +/- 0.25 mmol FFA x kg fat(-1) x h(-1); P < 0.05). Fat oxidation decreased (from 0.28 +/- 0.02 to 0.20 +/- 0.02 mmol FFA x kg lean body mass(-1) x h(-1); P < 0.002), as did the rate of appearance of FFAs available for intrahepatic reesterification (from 0.50 +/- 0.13 to 0.29 +/- 0.09 mmol FFA x kg fat(-1) x h(-1); P < 0.03). Fractional and absolute synthetic rates of VLDL apolipoprotein B-100 were unaltered. These kinetic changes were associated with a decrease in the waist-to-hip ratio but no significant change in fasting plasma lipid concentrations. Fasting plasma glucose concentrations increased after treatment (from 5.2 +/- 0.2 to 5.8 +/- 0.3 mmol/L; P < 0.01). CONCLUSIONS: Physiologic GH replacement has salutary effects on abnormal lipid kinetics in HLS. The effects are mediated by diminished lipolysis and hepatic reesterification rather than by increased fat oxidation.