Resting energy expenditure in Duchenne patients using home mechanical ventilation.

Nutritional status is both important and difficult to assess in patients with Duchenne muscular dystrophy (DMD), particularly in those requiring mechanical ventilation (MV). The current authors evaluated body composition (bio-impedancemetry), resting energy expenditure (REE; indirect calorimetry) and energy intake in 20 adult patients with DMD using home MV (nocturnal: n = 13; continuous: n = 7) and 12 age-matched healthy controls. The patients were smaller in height than the controls and had a lower body weight. Most of the reduction in body mass index was accounted for by a reduction in fat free mass (FFM). REE (kJ) was significantly reduced in the patients (4559+/-853 kJ x 24 h(-1) versus 7407+/-1312 kJ x 24 h(-1)), but the difference disappeared after correction for FFM. REE and FFM were correlated in both the controls and patients, but less strongly in the latter, the lower strength of the association being due to the patients using continuous MV (REE and FFM uncorrelated). The food intake of the patients was 1.2+/-0.4 greater than their REE. This study shows that patients with advanced forms of Duchenne muscular dystrophy have balanced energy intakes and resting energy expenditure.     

Resting energy expenditure and nutritional status in children with juvenile rheumatoid arthritis.

OBJECTIVE: Undernutrition is frequently encountered in children with juvenile rheumatoid arthritis (JRA). We assessed resting energy expenditure (REE) in relation to nutritional status and body composition in patients with JRA. METHODS: We selected 33 children (age 6 to 18 yrs) with JRA (13 oligoarticular, 10 polyarticular, 10 systemic JRA) and 17 controls matched for age and sex. Nutritional status was assessed for height, weight, and fat-free mass (FFM), and REE was measured with indirect calorimetry. RESULTS: Nutritional status in the patients with systemic JRA was diminished compared to the controls for height (140 vs. 159 cm; p<0.01) and FFM (28 vs. 38 kg; p = 0.03). Oligo and polyarticular patients with JRA had normal height and FFM. No significant differences existed in crude REE among the groups. However, after correcting REE for body weight and FFM, the patients with systemic JRA, compared to controls, had 18% higher REE per kg body weight (159 vs. 134 kJ/kg/day; p<0.01) and 21% higher REE per kg FFM (196 vs. 162 kJ/kg/day; p<0.01). Oligo and polyarticular JRA patients had 8% increased values for REE per kg body weight or FFM, but these differences were not statistically significant. CONCLUSION: Patients with systemic JRA show stunting, low FFM, and a significantly increased REE when nutritional status is taken into account. These data suggest that assessment of individual energy requirements should include correction for fat-free mass in the treatment of malnutrition in patients with systemic JRA.     

Body composition and resting energy expenditure in elderly male patients with chronic obstructive pulmonary disease

STUDY OBJECTIVE: Our study investigates nutritional status, resting energy expenditure (REE) and physical performance in elderly patients with stable COPD to identify any early conditions of hypermetabolism, malnutrition and sarcopenia. METHODS: Eighty-six males (40 stable COPD and 46 healthy subjects) over 65 years old were studied. All subjects underwent spirometry, blood gas analysis and a 6-min walking test (6MWT). Fat-free mass (FFM) and appendicular skeletal muscle mass (ASMM) were measured by dual energy X-ray absorptiometry (DEXA). REE was measured by indirect calorimetry. RESULTS: COPD patients had a lower FFM both expressed in kilograms and after correction for height squared. The prevalence of sarcopenia was higher for COPD subjects (38% vs 31%). REE, both in absolute values and adjusted for FFM was significantly higher in COPD patients. Hypermetabolism was found in 60% of COPD cases and 13.7% (P<0.01) of healthy subjects. No relationship was found in COPD patients between the measured/predicted REE ratio (REE(m)/REE(p)) and FEV1. In the hypermetabolic COPD subgroup, the REE(m)/REE(p) ratio correlated with 6MWT. CONCLUSIONS: Elderly patients with stable COPD develop an increased REE. This hypermetabolism seems to be independent of the severity of the pulmonary obstruction and to influence the patient's physical performance.     

No effect of gender on different components of daily energy expenditure in free living prepubertal children

BACKGROUND: There are limited and controversial data on the influence of gender on metabolic rate in prepubertal children. OBJECTIVE: To assess the effect of gender on resting energy expenditure (REE), activity-related energy expenditure (AEE), total energy expenditure (TEE) and physical activity level (PAL) in free-living prepubertal children. DESIGN: Cross-sectional study. SUBJECTS: 40 prepubertal children (24 boys, 16 girls, 4-11 y old (mean age: 7.0 +/- 1.2 y), BMI 13.1-32.0 kg/m2). MEASUREMENTS: Energy expenditure was measured by the combination of indirect calorimetry and individually calibrated 24 h heart rate monitoring. Body composition was assessed by anthropometrics and bioelectrical impedance analysis. Socio-cultural and socio-economic factors, as well as activities of daily living, were estimated by questionnaire for the parents. Boys and girls were matched for fat-free mass (FFM, boys: 25.9 +/- 8.5 kg; and girls: 24.4 +/- 4.5 kg, n.s.) and fat mass (FM, boys: 11.6-5.9 kg; and girls: 10.8 +/- 3.3 kg, n.s.). RESULTS: We found no sex difference in REE, AEE and TEE. PAL was 1.4 +/- 0.3 for boys and 1.2 +/- 0.4 for girls. REE and TEE were significantly related to FFM (r=0.62, r=0.81, r=0.60). FFM was found to be the most significant determinant of REE (r2=0.70). REE accounted for the largest part of the variance in TEE (r2=0.46). Gender had no significant effect. CONCLUSIONS: There is no effect of gender on energy expenditure in prepubertal children.     

Chronic sympathetic attenuation and energy metabolism in autonomic failure

The sympathetic nervous system regulates thermogenesis and energy homeostasis in humans. When activated it increases energy expenditure, particularly resting energy expenditure. Most human studies used acute infusion of β-blockers as a model to eliminate sympathetic stimulation and to examine the contribution of the sympathetic nervous system to energy metabolism and balance. Clinically, however, it is also important to assess the effect of chronic sympathetic attenuation on energy metabolism. In this context, we hypothesized that resting energy expenditure is decreased in patients with autonomic failure who, by definition, have low sympathetic tone. We measured 24-hour energy expenditure using whole-room indirect calorimeter in 10 adults with chronic autonomic failure (6 women; age, 64.9±9.1 years; body mass index, 25.2±4.4 kg/m(2)) and 15 sedentary healthy controls of similar age and body composition (8 women; age, 63.1±4.0 years; body mass index, 24.4±3.9 kg/m(2)). In 4 patients, we eliminated residual sympathetic activity with the ganglionic blocker trimethaphan. We found that, after adjusting for body composition, resting energy expenditure did not differ between patients with autonomic failure and healthy controls. However, resting energy expenditure significantly decreased when residual sympathetic activity was eliminated. Our findings suggest that sympathetic tonic support of resting energy expenditure is preserved, at least in part, in pathophysiological models of chronic sympathetic attenuation.     

L-tri-iodothyronine is a major determinant of resting energy expenditure in underweight patients with anorexia nervosa and during weight gain

OBJECTIVE: We aimed to define the effect of L-3,5,3'-tri-iodothyronine (T(3)) on metabolic adaptation in underweight patients with anorexia nervosa (AN) as well as during weight gain. METHODS: This involved clinical investigation of 28 underweight patients with AN, who were compared with 49 normal-weight controls. A subgroup of 17 patients was followed during weight gain. Resting energy expenditure was measured by indirect calorimetry. Body composition was measured by anthropometry as well as bioelectrical impedance analysis. Energy intake (EI) was assessed by a 3-day dietary record. Plasma concentrations of thyroid hormones (thyroxine (T(4)), T(3) and thyrotropin (TSH)) were analyzed by enzyme immunoassays. RESULTS: When compared with normal-weight women, underweight patients with AN had reduced fat mass (FM) (-71.3%), fat-free mass (FFM) (-13.1%), resting energy expenditure (REE) (-21.8%), T(3)- (-33.4%) and T(4)-concentrations (-19.8%) at unchanged TSH. REE remained reduced after adjustment for FFM (-24.6%). T(3) showed a close association with REE. This association remained after adjustment of REE for FFM. Treatment of underweight AN patients resulted in a mean weight gain of 8.3 kg. This was mainly explained by an increase in FM with small or no changes in FFM. REE and T(3) also increased (+9.3% and +33.3% respectively) at unchanged TSH and T(4). There was a highly significant association between weight gain-induced changes in T(3) and changes in adjusted REE (r = 0.78, P < 0.001, based on Pearson's correlation). An increase in plasma T(3) concentrations of 1.8 pmol/l could explain an increase in REE of 0.6 MJ/day (that is, a 32% increase in T(3) was associated with a 13% increase in REE). CONCLUSIONS: Our data provide evidence that the low T(3) concentrations add to metabolic adaptation in underweight patients with AN. During weight gain, increases in T(3) are associated with increases in REE, which is independent of FFM. Both results are evidence for a physiologic role of T(3) in modulation of energy expenditure in humans.     

Resting energy expenditure in chronic hepatitis C

BACKGROUND/AIMS: Hypermetabolism is considered to be of clinical interest in liver disease and in several chronic viral infections. Whether resting energy expenditure (REE) increases during chronic hepatitis C is not known. Our aims were: (a) to determine the metabolic state of patients with chronic hepatitis C, and (b) to evaluate the effects of interferon therapy on REE. METHODS: Forty-seven patients and 20 controls were studied. Sixteen patients failed to respond to interferon and 12 patients stopped the treatment during the first 2 months for various reasons. The 19 responders all received 1 year of interferon. REE (indirect calorimetry) and fat-free mass (FFM, bioelectric impedance analysis) were evaluated before (day 0) and after 90, 180, and 360 days of interferon. The virus load was evaluated in patients before treatment. RESULTS: On day 0, REE expressed as a ratio of FFM (REE/FFM) was higher in patients than in controls (129.2 +/- 14.7 vs 117.9 +/- 9.6 kJ kg FFM(-1) 24 h(-1), p<0.01), and was positively correlated with the viral load (r=0.45, p=0.01). On day 90, REE/FFM had significantly decreased in responders but it did not decrease in non-responders (p<0.01). In responders, REE/FFM on days 180 and 360 was similar to that of the controls. CONCLUSIONS: Chronic hepatitis C induces hypermetabolism that is normalized by interferon therapy in responders. The underlying mechanisms of chronic hepatitis C-induced hypermetabolism and its clinical relevance remain to be determined.     

The effect of gender and body composition method on the apparent decline in lean mass-adjusted resting metabolic rate with age

BACKGROUND: Declining resting energy expenditure (REE) is a hallmark of normal aging, but the cause of this decline remains controversial. Some, but not all, studies have shown that the decline in REE with age is eliminated after adjustment for fat-free mass (FFM). METHODS: We examined the effect of four body composition methods used to assess FFM (underwater weighing [UWW], bioimpedance analysis [BIA], tritium dilution, and total body potassium [TBK]) on the relationship between REE and age in 30 healthy men and 101 healthy women aged 18 to 87 years. RESULTS: The decline in REE with age was significant in women (-80.3 kJ/d/y, p < .004) but not in men (-46.9 kJ/d/y, p = .328). After adjustment for FFM, the decline in REE with age persisted when FFM was measured by BIA, UWW, or tritium dilution, but no decline was seen when TBK was used to adjust for FFM. In both women and men, fat mass was significantly associated with REE after adjusting for age and FFM. CONCLUSION: It is the decline in cell mass with age, detectable by TBK but not by other methods, rather than any metabolic alteration, that explains the decline in FFM-adjusted REE with age.     

No differences in rates of energy expenditure between post-obese women and their matched, lean controls.

Rates of energy expenditure at rest, during different daily activities and following a standardized liquid meal were compared in eight post-obese women, with a mean weight loss of 21.5 kg (range 14.1 to 33.3 kg) and eight controls who had never been overweight. Age, height, body mass index, fat-free mass and average daily energy intake were similar for both experimental groups. Resting metabolic rate averaged 23.04 cal/min/kg FFM (s.e.m. 1.14) in the post-obese and 22.70 cal/min/kg FFM (s.e.m. 0.64) in the controls on their first visit to the laboratory. Metabolic rates in the two groups rose in parallel as energy expenditure was increased by sitting, standing and walking at three different speeds (2.4, 3.9 and 5.4 km/h). At the highest walking speed energy expenditure averaged 95.30 cal/min/kg FFM (s.e.m. 4.18) in the post-obese and 93.42 cal/min/kg FFM (s.e.m. 2.97) in the control women. Comparisons of postprandial thermogenesis revealed no significant differences between the two groups. The results of the present study do not support the thesis that rates of energy expenditure, whether at rest, during different activities, or after eating, are reduced in post-obese women.     

The effect of sibutramine on resting energy expenditure and adrenaline-induced thermogenesis in obese females

BACKGROUND: Sibutramine, an inhibitor of serotonin and noradrenaline uptake, reduces appetite to cause weight loss. This study tested the hypothesis that an increase in energy expenditure also contributes to this weight loss. In addition, the effects of sibutramine on adrenaline induced changes in heart rate and cardiac output were determined METHODS: Nineteen obese females randomly received either sibutramine 15 mg daily or placebo for 12 weeks along with dietary advice. Resting energy expenditure (REE) was measured and then energy expenditure was measured during a 30 min infusion of adrenaline (25 ng/min/kg IBW). Cardiac output and heart rate, measured by Duplex Colour Doppler ultrasonography, were similarly measured in the basal state and post adrenaline. All measurements were recorded at baseline and then after 12 weeks. RESULTS: Ten patients who received sibutramine reduced their weight by 8.1+/-3.8% while 9 placebo treated subjects reduced their weight by 5.1+/-4.4%, P=0.13. In absolute terms, REE decreased in placebo subjects from 1500+/-201 kcal/24 h to 1357+/-231 kcal/24 h (9.4+/-9.9%) and in sibutramine subjects from 1540+/-184 kcal/24 h to 1444+/-128 kcal/24 h (5.3+/-12.0%), P=0.77. The increased weight loss in the sibutramine group was associated with an increase in the FFM adjusted REE (2.2+/-16.1%) unlike the expected decrease (5.8+/-9.5%) in the placebo group (P=0.11). There was some suggestion (P=0.09) that the usual positive correlation between loss of weight and decline in REE was lost in the sibutramine group (r=-0.30) compared with placebo (r=0.35). There was a negative correlation between loss of FFM and decline in REE/kg FFM and (P=0.029) which was not evident in placebo (P=0.83). Adrenaline induced energy expenditure was similar in the two groups at the end of the 12 week period and there were no significant cardiovascular changes between the two groups. CONCLUSIONS: Sibutramine limits the decline in REE associated with weight loss, equivalent to about 100 kcal/d. This could allow greater numbers of people to maintain a greater degree of weight loss.     

吸烟对早期糖尿病肾病静息能量消耗的影响

目的 观察吸烟对早期糖尿病肾病静息能量消耗(REE)的影响及与氧化应激和炎症反应之间的关系.方法 对31例吸烟和40例非吸烟的早期糖尿病肾病患者的一般情况、临床特征、REE、REE与去脂组织(FFM)的比值、氧化应激及炎症反应标志物进行比较分析.结果 吸烟组的REE/FFM比非吸烟组显著增高15.96%(P=0.001).相关分析提示,REE/FFM的增高与吸烟有关(t=0.395,P=0.001).氧化应激标志物丙二醛(MDA)、超氧化物歧化酶(SOD)和炎症反应标志物高敏C反应蛋白(hs-CRP)两组间差异有统计学意义(P＜0.05),脂联素、TNFα组间差异无统计学意义(P＞0.05),REE/FFM的增高与MDA、SOD、hs-CRP、脂联素、TNFα均不相关(P＞0.05).结论 吸烟可导致早期2型糖尿病肾病患者REE增加,引起氧化应激和炎症反应,但REE增高与氧化应激和炎症反应无关.     

Sleeping metabolic rate in relation to body mass index and body composition

OBJECTIVES: To determine whether patterns of sleeping metabolic rate (SMR) are altered in obesity. Specifically to determine the relationship between changes in SMR and body weight, body mass index (BMI, kg/m(2)), and fat-free mass (FFM); and to compare resting metabolic rate (RMR) with SMR during different periods of sleep. SUBJECTS: Eighteen healthy, pre-menopausal, obese (BMI >30, n=9) and non-obese (BMI <30, n=9), female subjects (six Caucasians and 12 African-Americans), with an average age of 36 y (range 22-45). MEASUREMENTS: Total energy expenditure (TEE or 24 h EE), metabolic rate (MR), SMR (minimum, average and maximum) and resting metabolic rate (RMR) or resting energy expenditure (REE) measured by human respiratory chamber, and external mechanical work measured by a force platform within the respiratory chamber. Physical activity index (PAL) was derived as TEE/REE. Body composition was determined by dual-energy X-ray absorptiometry (DXA). RESULTS: SMR decreased continuously during sleep and reached its lowest point just before the subject was awakened in the morning by the research staff. Although averages for RMR and SMR were similar, RMR was lower than SMR at the beginning of the sleeping period and higher than SMR in the morning hours. The rate of decrease in SMR was faster with increasing body weight (-0.829, P<0.0001), BMI (correlation factor -0.896, P<0.0001) and FFM (-0.798, P=0.001). The relationship between the slope of SMR decrease and BMI (y=-5 x 10(-6)x(2)+0.0002x-0.0028) is highly significant, with a P-value of <0.0001 and r(2) value of 0.9622. CONCLUSIONS: The rate of decline in metabolic rate during sleep is directly related to body weight, BMI and FFM. Average SMR tends to be lower than RMR in obese subjects and higher than RMR in non-obese subjects.     

Physiologic changes after diet combined with structured aerobic exercise or lifestyle activity

Moderate intensity physical activity achieved through changes in lifestyle may promote weight management. However, little is known about changes in physiologic and metabolic variables when patients lose weight using moderate intensity lifestyle activity instead of traditional structured vigorous aerobic exercise. To compare changes in resting metabolic energy expenditure (REE), fat mass (FM), and fat-free mass (FFM) associated with a 12-week weight loss program combined with either: (1) aerobic exercise (AER); or (2) lifestyle activity (LIFE), we randomized 39 overweight adults (mean body mass index [BMI] = 30.9 +/- 2.8 kg/m(2)) to either diet plus AER (N = 18) or diet plus LIFE (N = 21). Both groups consumed a self-selected diet of 1,200 to 1,800 kcal/d (5,021 to 7,531 kJ/d). The AER group performed vigorous aerobic exercise for up to 45 minutes 3 to 4 d/wk. The LIFE group accumulated 30 minutes of moderate intensity physical activity on most days of the week. Compliance with the respective protocols was monitored on a weekly basis. REE was measured before and after treatment via open-circuit spirometry. The AER group decreased body weight by 8.4% (P<.001)while the LIFE had a reduction of 6.7% (P <.001) after treatment. Over the course of the interventions, the AER and LIFE groups experienced 10.9% (P <.001) and 10.2% (P <.001) reductions in REE, respectively. Aerobic exercise did not prevent reductions in REE to a greater extent than did lifestyle activity in patients consuming a reduced calorie diet. Change in REE was not related to changes in FFM or FM for either group, and there were no differences between groups in reductions of REE, weight, FM, or FFM. A program of diet plus lifestyle physical activity may be a suitable alternative for dieting adults who have difficulty adhering to a program of vigorous activity.     

Association of fatigue with an acute phase response in sarcoidosis.

The pathophysiological explanation for fatigue, one of the most common symptoms in sarcoidosis, still has to be elucidated. It was hypothesized that the presence of fatigue is associated with an acute phase response in sarcoidosis. A cross-sectional study was performed in 38 sarcoidosis patients. Resting energy expenditure (REE) was measured in the fasting state by indirect calorimetry using a ventilated hood and adjusted for fat-free mass (FFM). Patients with fatigue (n=25) also suffered more frequently from other symptoms, such as exercise intolerance (p=0.01), the need for sleep (p=0.02) and weight loss (p=0.01), compared to those without fatigue (n=13). However, no relationship was found between fatigue and serum angiotensin-converting enzyme (sACE) or lung function impairment. Patients with fatigue had higher levels of C-reactive protein (CRP) (11.4+/-6.8 microg x mL(-1), p<0.0001) and REE adjusted for FFM (33.0+/-3.7 kcal x kg FFM(-1), p<0.003) compared to those without fatigue (3.2+/-2.2 mg x mL(-1); 29.2+/-2.8 kcal x kg FF(-1)). Furthermore, REE/FFM was significantly related to CRP (r=0.54, p=0.001). This study confirms the presence of an acute phase response as indicated by metabolic derangements and a moderate increase in C-reactive protein levels in sarcoidosis, particularly in those patients with constitutional symptoms. Future studies should focus on the clinical relevance and therapeutic implications of these findings.     

Resting energy expenditure and body composition in bedridden institutionalized elderly women with advanced-stage pressure sores

BACKGROUND: Our study investigated nutritional status, body composition, and resting energy expenditure (REE) in elderly patients with advanced-stage pressure sores (PS), in addition to researching any hypermetabolic condition and its relationship with PS size. METHODS: The study involved 52 institutionalized bedridden elderly women (aged 83.7 +/- 6.3 years), divided into two groups: 23 with advanced-stage (stage 3 and 4) PS and 29 without PS. Albumin, prealbumin, and retinol-binding protein were measured in all patients, and fat-free mass (FFM) and fat mass (FM) were obtained by dual-energy x-ray absorptiometry (DEXA). REE was measured by indirect calorimetry and predicted with the Harris-Benedict formula. PS area and volume were also measured. RESULTS: The elderly women with and without PS were comparable in age, FFM, and FM. Mean albumin, prealbumin, and retinol-binding protein values were lower in cases with PS. Unadjusted mean REE was significantly higher in patients with PS (1212.3 +/- 236.7 vs 1085.5 +/- 161.3 kcal/d; p <.05), even after adjusting for FFM or expressed per kilogram of body weight (25.8 +/- 6.7 vs 21.1 +/- 4.0 kcal/d/kg; p <.01). Hypermetabolism, i.e., a measured REE > 110% of the predicted REE, was seen in 74% of patients with PS and 38% of controls. The difference between measured and predicted REE (DeltaREE) correlated with PS volume (r = 0.58; p <.01), but not with area. CONCLUSION: Advanced-stage PS in elderly women are associated with a hypermetabolic state that is influenced by the volume of the PS.     

Effect of chronic treatment with beta-blockers on resting energy expenditure in obese hypertensive patients during a low-calorie and physical training program

BACKGROUND AND AIM: To evaluate whether chronic treatment with beta-blockers influences resting energy expenditure (REE) and weight loss after a period of diet and physical activity in obese hypertensive patients. METHODS AND RESULTS: Seventy-eight obese hypertensive patients (24 males and 54 females) aged 53.7 +/- 11.1 years with mean BMI of 42.4 +/- 5.8 kg/m2 were enrolled. Thirty-eight patients were using beta-blockers while 40 patients who had not received beta-blockers in the past 6 months were the control group. REE was measured with indirect calorimetric method. Total body fat mass, total body fat-free mass (FFM) and total body water (W) were determined by bioelectrical impedance analysis. Patients and controls underwent a structured physical training program and a hypocaloric diet for a period of 31.6 +/- 10.6 days. Measured REE in patients taking beta-blockers was 1818 +/- 309 kcal/24 h and 1853 +/- 348 kcal/24 h in patients not taking beta-blockers; p = non significant. Weight and BMI loss were similar between the two groups and were respectively -6.43 +/- 2.62 kg and -2.42 +/- 0.91 kg/m2 in the beta-blocker group and -7.49 +/- 3.10 kg, -2.78 +/- 1.03 kg/m2 in the non beta-blocker group. Body composition was similar in the two groups. In the comparison between patients treated with selective beta 1-adrenoceptors blockers and non selective beta-blockers we found a significant difference in REE (1704 +/- 283 vs 1974 +/- 278; p = 0.012) and in weight loss (-5.6 +/- 2.4 vs -7.5 +/- 2.7; p = 0.048) at the end of study. CONCLUSIONS: Beta-blockers are not associated with a lower REE in obese subjects compared to other antihypertensive treatment. Use of non selective beta-adrenergic blockers is associated with a higher REE and weight loss compared to use of selective beta 1-adrenergic blockers. Non selective beta-blockers could be indicated among first choice drugs in hypertensive severely obese subjects without contraindications to beta-blockade.     

Nutrient oxidation patterns and protein metabolism in lean and obese subjects

The immediate metabolic response to eating has been compared in a group of grossly obese subjects (W/H2 = 45) with that in lean controls (W/H2 = 22). Dietary intake of energy for obese subjects was based on their estimated basal energy expenditure for ideal body weight (given at an hourly rate of 3 X BMR over a 4-h period). Lean subjects were measured twice: control 1 with the same intake of energy as the obese in terms of ideal body weight and control 2 with the same energy intake in relation to each subject's measured resting energy expenditure (2.2 X REE). The changes in energy expenditure and nutrient disposal with the onset of eating have been assessed by a method of combined respiratory gas analysis and intravenous infusion of 13C-labelled leucine. Leucine kinetics were used to quantitate rapid changes in protein oxidation and to assess protein synthesis and degradation. 1) Total energy expenditure was 20-30 per cent greater in obese subjects than lean subjects in fasting and feeding. Energy expenditure expressed per kg fat-free mass, from D2O dilution, was similar in obese and lean subjects in both fasting (5.8 v. 5.5 kJ/kg FFM/h) and feeding [6.7 v. 6.3 (Control 2) kJ/kg FFM/h]. 2) The onset of eating was associated with increased carbohydrate and protein oxidation with decreased fat oxidation in both lean and obese individuals. In obese subjects, however, both the decrease in fat oxidation and the increase in protein oxidation were significantly smaller (P less than 0.05) than the corresponding increments in lean subjects (Control 2). 3) The rate of protein synthesis was significantly (P less than 0.05) higher in obese subjects both in the fasting state (99 v. 84 mumols leucine/kg FFM/h) and in the fed state [94 v. 67 (Control 2) mumols leucine/kg FFM/h]. The rate of protein degradation was also higher in obese individuals in fasting (117 +/- 6 v. 106 +/- 4 mumol leucine/kg FFM/h) and feeding [65 +/- 4 v. 54 +/- 6 (Control 2) mumol leucine/kg FFM/h] though these differences are not statistically significant (P greater than 0.05). 4) The observed differences between obese and lean individuals in protein and energy metabolism in the fasted state and in the immediate response to eating do not support a hypothesis of greater metabolic efficiency in obesity.     

Body composition and resting energy expenditure in humans: role of fat, fat-free mass and extracellular fluid

OBJECTIVE: The objective of this study was to determine whether there are independent effects of extracellular fluid volume (ECF) and fat mass (FM) on resting energy expenditure (REE) relative to fat-free mass (FFM) in adult men and women. METHODS: Multiple linear regression analysis was used to relate REE, as determined by indirect calorimetry, to FFM and FM (measured using dual energy X-ray absorptiometry) and ECF (measured using bromide space and/or the radiosulfate washout space) in 153 women and 100 men with varying amounts of body fat. RESULTS: REE correlated significantly with FFM and FM in women (r=0.65 and r=0.63, both P<0.001) and men (r=0.62 and r=0.48, both P<0.001, FFM and FM, respectively). In a multiple linear regression analysis FFM, FM and age significantly contributed to the ability to predict REE in both genders. The models that were derived were not significantly different between women and men. In women the contribution to REE from FM was easier to detect when FM was greater. Adjustment of FFM for ECF did not improve the relationship between FFM and REE. CONCLUSIONS: FFM, FM and age are significant, independent predictors of REE in both men and women. Adjustment of FFM for ECF does not improve the ability of FFM to predict REE, which suggests that ECF is a highly integrated component of FFM in healthy adults. Expressing REE relative to FFM alone will introduce errors when lean and obese populations are compared.     

Changes in body composition in patients with severe lipodystrophy after leptin replacement therapy

Leptin, an adipocyte hormone, when replaced in patients with lipodystrophy, improves insulin resistance, hyperglycemia, dyslipidemia, and hepatic steatosis. Changes in body composition accompany this metabolic improvement. We studied 14 patients (3 men and 11 women); 12 of who had generalized lipodystrophy (7 congenital, 5 acquired), and 2 patients had partial lipodystrophy. Body composition and related parameters were evaluated at baseline and after 4 and 12 months of leptin therapy. Baseline body mass index (BMI) was 21.7 +/- 0.8 kg/m(2), the percent body fat was 9.5% +/- 1.6%, and the serum leptin level was 1.7 +/- 0.3 ng/mL. On treatment, serum leptin levels increased by 10-fold. All patients reported a decrease in appetite on therapy. After 4 months, both daily caloric intake and resting energy expenditure (REE) decreased. The liver volume decreased (baseline = 3,055 +/- 281 cm(3); 4 months = 2,433 +/- 243 cm(3), P =.006). Dual energy x-ray absorptiometry (DEXA) demonstrated significant decreases in fat mass (5.4 +/- 0.8 kg to 5.0 +/- 0.8 kg; P =.003) and lean body mass (51.2 +/- 3.2 kg to 48.3 +/- 3.4 kg; P =.003) at 4 months on therapy. There was no impact of leptin therapy on bone mineral content, mineral density, and metabolism. Changes in body composition occurred during the first 4 months of leptin therapy, but then stabilized and were sustained thereafter.