Validation of energy expenditure and macronutrient oxidation measured by two new whole-room indirect calorimeters.

OBJECTIVE: The aim of this study was to validate two new whole-room indirfect calorimeters according to Room Indirect Calorimetry Operating and Reporting Standards (RICORS 1.0). METHODS: For technical validation, 16 propane combustion tests were performed to determine accuracy and precision of energy expenditure (EE) and ventilation rates of oxygen (VO2 ), carbon dioxide (VCO2 ), and respiratory exchange ratio (VCO2 /VO2 ). For biological validation, eight participants (mean [SD], age 24.1 [2.5] years; BMI 24.3 [3.1] kg/m2 ) underwent four 24-hour protocols under highly standardized conditions: (1) isocaloric sedentary, (2) fasting sedentary, (3) isocaloric active, and (4) fasting active. Reliability (coefficients of variation [CV]) and minimal detectable changes (MDC) were calculated for 24-hour EE, sleeping metabolic rate (SMR), physical activity energy expenditure (PAEE), thermic effect of food (TEF), and macronutrient oxidation rates. RESULTS: Technical validation showed high reliability and recovery rates for VO2 (0.75% and 100.8%, respectively), VCO2 (0.49% and 100.6%), and EE (0.54% and 98.2%). Biological validation revealed CV and MDC for active conditions of 1.4% and 4.3% for 24-hour EE, 1.7% and 5.9% for SMR, and 30.2% and 38.4% for TEF, as well as 5.8% and 10.5% for PAEE, respectively. Mean CV and MDC for macronutrient oxidation rates were 9.9% and 22.9%, respectively. CONCLUSIONS: The precision of 24-hour EE and SMR was high, whereas it was lower for PAEE and poor for TEF.

Effects of CPAP on energy expenditure in obese obstructive sleep apnoea patients: A pilot study.

We conducted a placebo-controlled crossover pilot study investigating the effects of 2 mo of active and sham continuous positive airway pressure (CPAP) on energy expenditure (EE) via whole-room indirect calorimetry in three obese obstructive sleep apnoea (OSA) patients. Total 24-h (active: 2970 ± 254 kcal/d, sham: 2705 ± 217 kcal/d; p = 0.015) and mean sleeping (active: 1.60 ± 0.20 kcal/min; sham: 1.47 ± 0.17 kcal/min; p = 0.038) EE were significantly increased after active vs. sham CPAP. Findings suggest that CPAP may correct a hypoxia-related adaptive decrease in thermogenesis.

Experimental sleep curtailment causes wake-dependent increases in 24-h energy expenditure as measured by whole-room indirect calorimetry.

BACKGROUND: Epidemiologic evidence has shown a link between short sleep and obesity. Clinical studies suggest a role of increased energy intake in this relation, whereas the contributions of energy expenditure (EE) and substrate utilization are less clearly defined. OBJECTIVE: Our aim was to investigate the effects of sleep curtailment on 24-h EE and respiratory quotient (RQ) by using whole-room indirect calorimetry under fixed-meal conditions. DESIGN: Ten females aged 22-43 y with a BMI (in kg/m²) of 23.4-27.5 completed a randomized, crossover study. Participants were studied under short- (4 h/night) and habitual- (8 h/night) sleep conditions for 3 d, with a 4-wk washout period between visits. Standardized weight-maintenance meals were served at 0800, 1200, and 1900 with a snack at 1600. Measures included EE and RQ during the sleep episode on day 2 and continuously over 23 h on day 3. RESULTS: Short compared with habitual sleep resulted in significantly higher (± SEM) 24-h EE (1914.0 ± 62.4 compared with 1822.1 ± 43.8 kcal; P = 0.012). EE during the scheduled sleep episode (0100-0500 and 2300-0700 in short- and habitual-sleep conditions, respectively) and across the waking episode (0800-2300) were unaffected by sleep restriction. RQ was unaffected by sleep restriction. CONCLUSIONS: Short compared with habitual sleep is associated with an increased 24-h EE of ~92 kcal (~5%)--lower than the increased energy intake observed in prior sleep-curtailment studies. This finding supports the hypothesis that short sleep may predispose to weight gain as a result of an increase in energy intake that is beyond the modest energy costs associated with prolonged nocturnal wakefulness.

Energy expenditure and physical activity in recovering malnourished infants.

Background. Malnourished infants are small for age and weight. Objectives. Determine profiles in 24-hour energy metabolism in recovering malnourished infants and compare to similarly aged healthy controls. Methods. 10 malnourished infants (58.1 +/- 5.9 cm, 7.7 +/- 5.6 months) were healthy prior to spending 22 hours in the Enhanced Metabolic Testing Activity Chamber for measurement of EE (kcal/min), sleeping metabolic rate (SMR; kcal/min), respiratory quotient (RQ; VCO(2)/VO(2)), and physical activity (PA; oscillations in wt/min/kg body weight). Metabolic data were extrapolated to 24 hours (kcal/kg/d). Energy intake (kcal/kg/d) and the proportions (%) of carbohydrate, protein, and fat were calculated. Anthropometrics for malnourished infants were obtained. Statistical differences (P < .05) between groups were determined (SPSS, version 13). Results. In comparison to controls, malnourished infants were lighter (4.1 +/- 1.2 versus 7.3 +/- 0.8 kg; P < .05), had less body fat % (10.3 +/- 7.6 versus 25.7 +/- 2.5), and lower BMI (12.0 +/- 1.7 versus 15.5 +/- 1.5; P < .05). In contrast, they had greater energy intake (142.7 +/- 14.6 versus 85.1 +/- 25.8; P < .05) with a greater percentage of carbohydrates (55.1 +/- 3.9 versus 47.2 +/- 5.2; P < .05). However, malnourished infants had greater 24-hour EE (101.3 +/- 20.1 versus 78.6 +/- 8.4; P < .05), SMR (92.6 +/- 17.1 versus 65.0 +/- 3.9; P < .05), and RQ (1.00 +/- 0.13 versus 0.86 +/- 0.08; P < .05) along with a lower amount of PA (2.3 +/- 0.94 versus 4.0 +/- 1.5; P < .05). Conclusions. Malnourished infants require more energy, possibly for growth.

Energy expenditure in chow-fed female non-human primates of various weights.

BACKGROUND: Until now no technology has been available to study energy metabolism in monkeys. The objective of this study was to determine daily energy expenditures (EE) and respiratory quotients (RQ) in female monkeys of various body weights and ages. METHODS: 16 socially reared Bonnet Macaque female monkeys [5.5 +/- 1.4 kg body weight, modified BMI (length measurement from head to base of the tail) = 28.8 +/- 6.7 kg/crown-rump length, m2 and 11.7 +/- 4.6 years] were placed in the primate Enhanced Metabolic Testing Activity Chamber (Model 3000a, EMTAC Inc. Santa Barbara, CA) for 22-hour measurements of EE (kcal/kg) and RQ (VCO2/VO2). All were fed monkey chow (4.03 kcal/g) ad-libitum under a 12/12 hour light/dark cycle. Metabolic data were corrected for differences in body weight. Results were divided into day (8-hours), dark (12 hours) and morning (2-hours) periods. Data analysis was conducted utilizing SPSS (Version 13). RESULTS: Modified BMI negatively correlated with 22-hour energy expenditure in all monkeys (r = -0.80, p < 0.01). The large variability of daily energy intake (4.5 to 102.0 kcal/kg) necessitated division into two groups, non-eaters (< 13 kcal/kg) and eaters (> 23 kcal/kg). There were reductions (p < 0.05) in both 22-hour and dark period RQs in the "non-eaters" in comparison to those who were "eaters". Monkeys were also classified as "lean" (modified BMI < 25) or "obese" (modified BMI > 30). The obese group had lower EE (p < 0.05) during each time period and over the entire 22-hours (p < 0.05), in comparison to their lean counterparts. CONCLUSION: The EMTAC proved to be a valuable tool for metabolic measurements in monkeys. The accuracy and sensitivity of the instrument allowed detection of subtle metabolic changes in relation to energy intake. Moreover, there is an association between a reduction of energy expenditure and a gain in body weight.

Lower energy expenditures in infants from obese biological mothers.

BACKGROUND: Previous studies in adults have found that a lower resting metabolic rate is a predictor of future body weight gain. METHODS: To determine if energy expenditures are reduced in infants born to obese mothers, 21 healthy infants (3.9 +/- 1.9 months) born to lean (n = 7, BMI < 25 kg/m2), overweight (n = 7, BMI between 25-30) and obese (n = 7, BMI>30) mothers, respectively, participated in this study. Measurements of infant weight, length and skin-fold thicknesses, and mother's weight and height were obtained. Infant energy expenditure was measured for 4-hours using the Enhanced Metabolic Testing Activity Chamber. Metabolic data were extrapolated to 24-hours and adjusted for differences in age and body composition using linear regression analysis (SPSS, version 13) and expressed as kcal/day. Differences between the three groups were determined by one way ANOVA with the Bonferroni Post Hoc test procedure (p < 0.05). RESULTS: Infants born to obese mothers had a greater BMI (16.7 +/- 1.2) than those from both the overweight (15.3 +/- 1.4, p < 0.05) and lean groups (15.1 +/- 1.3; p < 0.05). The infants of obese mothers had greater body fat (26.8 +/- 2.1) than those from the overweight group (22.4 +/- 5.0, p < 0.06). Infant BMI correlated (r = 0.53; p < 0.01) with that of their mothers. Extrapolated 24-h EE (kcal/d) correlated with fat-free mass (r = 0.94; p < 0.01). Infants extrapolated 24-h EE from both obese (472.1 +/- 30.7 kcal/d; p < 0.05) and overweight groups (471.8 +/- 39.5; p < 0.05) were lower than those of the lean group (532.4 +/- 30.7). CONCLUSION: Lower extrapolated 24-h energy expenditure was present in infants of overweight and obese biological mothers during the first three to six months of life. Furthermore, these infants showed increased BMI and body fat. If these changes are unchecked future childhood obesity may result.

Energy expenditures & physical activity in rats with chronic suboptimal nutrition.

BACKGROUND: Sub-optimally nourished rats show reduced growth, biochemical and physiological changes. However, no one has assessed metabolic rate adaptations in rats subjected to chronic suboptimal nutrition (CSN). In this study energy expenditure (EE; kcal/100 g body weight) and physical activity (PA; oscillations in weight/min/kg body weight) were assessed in rats subjected to three levels of CSN. RESULTS: Body weight gain was diminished (76.7 +/- 12.0 and 61.6 +/- 11.0 g) in rats fed 70 and 60% of the ad-libitum fed controls which gained more weight (148.5 +/- 32.3 g). The rats fed 80% gained weight similarly to controls (136.3 +/- 10.5 g). Percent Fat-free body mass was reduced (143.8 +/- 8.7 and 142.0 +/- 7.6 g) in rats fed 70 and 60% of ad-libitum, but not in those fed 80% (200.8 +/- 17.5 g) as compared with controls (201.6 +/- 33.4 g). Body fat (g) decreased in rats fed 80% (19.7 +/- 5.3), 70% (15.3 +/- 3.5) and 60% (9.6 +/- 2.7) of ad-libitum in comparison to controls (26.0 +/- 6.7). EE and PA were also altered by CSN. The control rats increased their EE and PA during the dark periods by 1.4 +/- 0.8 and 1.7 +/- 1.1 respectively, as compared with light the period; whereas CSN rats fed 80 and 70% of ad-libitum energy intake had reduced EE and PA during the dark periods as compared with the light period EE(7.5 +/- 1.4 and 7.8 +/- 0.6 vs. 9.0 +/- 1.2 and 9.7 +/- 0.8; p < 0.05, respectively), PA(3.1 +/- 0.8 and 1.6 +/- 0.4 vs. 4.1 +/- 0.9 and 2.4 +/- 0.4; p < 0.05) and RQ (0.87 +/- 0.04 and 0.85 +/- 0.5; vs. 0.95 +/- 0.03 and 0.91 +/- 0.05 p < 0.05). In contrast, both light (7.1 +/- 1.4) and dark period (6.2 +/- 1.0) EE and PA (3.4 +/- 0.9 and 2.5 +/- 0.5 respectively) were reduced in rats fed 60% of ad-libitum energy intake. CONCLUSION: CSN rats adapt to mild energy restriction by reducing body fat, EE and PA mainly during the dark period while growth proceeds and lean body mass is preserved. At higher levels of energy restrictions there is decreased growth, body fat and lean mass. Moreover EE and PA are also reduced during both light and dark periods.

New equations for calculating the components of energy expenditure in infants.

OBJECTIVES: To derive new equations for 24-hour energy expenditure (24-h EE; kcal/d) and resting (RMR; kcal/d) and sleeping metabolic rates (SMR; kcal/d) in young infants by using the Enhanced Metabolic Testing Activity Chamber (EMTAC). METHODS: Data from 50 (25 male/25 female) healthy normally growing infants (4.9 +/- 1.6 months, 7.1 +/- 1.4 kg, 65 +/- 5 cm) who had 24-h EE, RMR, and SMR extrapolated from 4- to 6-hour metabolic measurements in the EMTAC were used to derive new equations for 24-h EE, RMR, and SMR. Equations were derived by means of multiple regression analysis (SPSS 8.0), with weight alone or with length and weight entered as independent variables. Similar data from 10 additional test infants (4 male/6 female, 5.1 +/- 0.6 months, 7.5 +/- 1.0 kg, 65 +/- 5 cm) were used to cross-validate the new equations. RESULTS: Twenty-four-hour EE, RMR, and SMR were 79.6 +/- 19.2, 66.8 +/- 15.1, and 62.3 +/- 10.3 kcal/kg per day, respectively. No differences existed in RMR (kcal/kg per day) from the 10 test infants between the weight (68.6 +/- 1.9) and height-weight based equations (68.4 +/- 6.1) or that measured by the EMTAC (67.6 +/- 10.2). Weight was the major predictor of 24-h EE, RMR, and SMR. The WHO, Schofield-weight and weight-height equations underestimated (P <.05) by 19%, whereas the new equations were within 4% of RMR obtained from the EMTAC. CONCLUSIONS: The new equations for assessing energy requirements in healthy infants are more accurate than those previously published that underestimated 24-h EE by 15 kcal/kg per day.