RESUMO
OBJECTIVES: To measure postabsorptive fat oxidation (F(ox)) and to assess its association with body composition (lean body mass [LBM] and body fat mass [BFM]) and pubertal development. DESIGN: We studied 235 control (male/female ratio = 116/119; age [mean +/- SD]: 13.1 +/- 1.7 years; weight: 45.3 +/- 10.5 kg; LBM: 34.3 +/- 7.1 kg; BFM: 11.0 +/- 4.5 kg) and 159 obese (male/female ratio = 93/66; age: 12.9 +/- 2.1 years; weight: 76.2 +/- 19.1 kg; LBM: 47.4 +/- 10.9 kg; BFM: 28.8 +/- 9.2 kg) adolescents. Postabsorptive F(ox) was calculated from oxygen consumption, carbon dioxide production, and urinary nitrogen as measured by indirect calorimetry and Kjeldahl's method, respectively. Body composition was determined by anthropometry. RESULTS: Postabsorptive F(ox) (absolute value and percentage of resting metabolic rate) was significantly (p < 0.001) higher in the obese adolescents (76.7 +/- 26.3 gm/24 hours, 42.3% +/- 18.7%) than in the control subjects (40.0 +/- 26.3 gm/24 hours, 28.7% +/- 17.0%), even if adjusted for LBM. F(ox) corrected for BFM was similar in control and in obese children, but was significantly lower in girls compared with boys (control male subjects: 62.1 +/- 29.1 gm/24 hours, control female subjects: 51.6 +/- 28.4 gm/24 hours, obese male subjects: 57.3 +/- 29 gm/24 hour, obese female subjects: 45.0 +/- 28.4 gm/24 hours). BFM and LBM showed a significant positive correlation with F(ox). By stepwise regression analysis the most important determinant of F(ox) was BFM in obese and LBM in control children. There was a significant rise in F(ox) during puberty; however, it was mainly explained by changes in body composition. CONCLUSIONS: Obese adolescents have higher F(ox) rates than their normal-weight counterparts. Both LBM and fat mass are important determinants of F(ox).
Assuntos
Tecido Adiposo/metabolismo , Composição Corporal , Obesidade/metabolismo , Puberdade/metabolismo , Adolescente , Análise de Variância , Calorimetria Indireta , Dióxido de Carbono/metabolismo , Metabolismo Energético , Feminino , Humanos , Masculino , Nitrogênio/urina , Consumo de Oxigênio , Análise de RegressãoRESUMO
OBJECTIVE: To study the relationship between the energy expenditure for activity (EEAct), the level of activity and adiposity in a group of 9-year-old boys (n = 28) with different body composition (body weight, 38 +/- 10 kg [range, 23 to 66 kg]; fat mass, 23% +/- 10% [range, 8% to 42%]). METHODS: Total energy expenditure (TEE) was measured by means of the heart-rate monitoring method. EEAct was calculated as TEE-(REE+0.1 TEE), where REE is the postabsorptive resting energy expenditure and 0.1 TEE corresponds to the postprandial thermogenesis (approximately 10% of TEE). RESULTS: TEE, REE, and EEAct were 9388 +/- 1859, 5154 +/- 642, and 3295 +/- 1356 l J/day, respectively. Daily time devoted to sedentary and nonsedentary activities averaged 290 +/- 155 minutes (range, 69 to 621) and 534 +/- 150 minutes (range, 180 to 783), respectively. Time spent on sedentary activities was directly proportional to fat mass percentage (r = 0.46; p < 0.05). It was the only variable, among the free-living physical-activity [EEAct, TEE/(REE+0.1 TEE) ratio, time spent in nonsedentary and sedentary activities] variables, which remained significantly in the multiple step-down regression analysis final equation (r = 0.46; p < 0.05). CONCLUSIONS: The positive relationship between adiposity and time spent on sedentary activities in 9-year-old boys suggests the importance of the role played by muscular activity, at least in the maintenance of obesity in childhood. Prepubertal children should be encouraged to spend less time on sedentary activities to treat and prevent their obesity.
Assuntos
Tecido Adiposo/anatomia & histologia , Índice de Massa Corporal , Atividade Motora , Composição Corporal , Estatura , Regulação da Temperatura Corporal , Peso Corporal , Dióxido de Carbono/metabolismo , Criança , Digestão , Ingestão de Alimentos , Metabolismo Energético/fisiologia , Frequência Cardíaca/fisiologia , Humanos , Masculino , Monitorização Ambulatorial , Músculo Esquelético/fisiologia , Obesidade/fisiopatologia , Obesidade/prevenção & controle , Obesidade/terapia , Consumo de Oxigênio , Esforço Físico/fisiologia , Puberdade , Troca Gasosa Pulmonar , Análise de Regressão , Descanso/fisiologia , Dobras Cutâneas , Fatores de TempoRESUMO
OBJECTIVES: The validity of equations for the calculation of resting metabolic rate (RMR) were studied and new predictive equations were developed. STUDY DESIGN: The RMR was measured in a sample of 371 10- to 16-year-old prepubertal and postpubertal children. The study group included 193 male (116 nonobese and 77 obese) and 178 female (119 nonobese and 59 obese) subjects; for each group the RMRs predicted from five equations recommended for this age group were compared. The RMR was assessed by indirect calorimetry with a ventilated hood system for 45 minutes after an overnight fast. Body composition was estimated from skin-fold measurements. RESULTS: The mean +/- SD RMR was found to be 5600 +/- 972 kJ/24 hr and 7223 +/- 1220 kJ/24 hr in nonobese and obese boys, and 5112 +/- 632 kJ/24 hr and 6665 +/- 1106 kJ/24 hr in nonobese and obese girls, respectively. All five equations applicable to 10- to 16-year-old children overestimated RMR by 7.5% to 18.1% (p < 0.001 for each equation). Stepwise regression analysis, with independent variables such as age, weight, height, and gender, allowed development of new predictive equations for the calculation of RMR in 10- to 16-year-old boys (RMR = 50.9 Weight (kg) + 25.3 Height (cm) -50.3 Age (yr) + 26.9; R2 = 0.884, p < 0.0001) and girls (RMR = 51.2 Weight (kg) + 24.5 Height (cm) - 207.5 Age (yr) + 1629.8; R2 = 0.824, p < 0.0001). These predictive equations were tested in a second, independent cohort of children (80 male and 61 female subject) and were found to give a reliable estimate of RMR in 10- to 16-year-old obese and nonobese adolescents. CONCLUSIONS: The currently used predictive equations overestimate RMR in 10- to 16-year-old children. The use of the newly developed equations is recommended.
Assuntos
Obesidade/metabolismo , Adolescente , Antropometria , Índice de Massa Corporal , Calorimetria , Criança , Estudos de Coortes , Metabolismo Energético , Feminino , Humanos , Masculino , Estudos Prospectivos , Análise de Regressão , Dobras CutâneasRESUMO
The purpose of this study was to measure postabsorptive fat oxidation at rest and to assess the association between fat mass and fat oxidation rate in prepubertal children, who were assigned to two groups: 35 obese children (weight, 44.5 +/- 9.7 kg; fat mass; 31.7 +/- 5.4%) and 37 nonobese children (weight, 30.8 +/- 6.8 kg; fat mass, 17.5 +/- 6.7%). Postabsorptive fat oxidation expressed in absolute value was significantly higher in obese than in nonobese children (31.4 +/- 9.7 mg/min vs 21.9 +/- 10.2 mg/min; p < 0.001) but not when adjusted for fat-free mass by analysis of covariance with fat-free mass as the covariate (28.2 +/- 10.6 mg/min vs 24.9 +/- 10.5 mg/min). In obese children and in the total group, fat mass and fat oxidation were significantly correlated (r = 0.65; p < 0.001). The slope of the relationship indicated that for each 10 kg additional fat mass, resting fat oxidation increased by 18 gm/day. We conclude that obese prepubertal children have a higher postabsorptive rate of fat oxidation than nonobese children. This metabolic process may favor the achievement of a new equilibrium in fat balance, opposing further adipose tissue gain.
Assuntos
Tecido Adiposo/metabolismo , Obesidade/metabolismo , Obesidade/prevenção & controle , Puberdade/metabolismo , Aumento de Peso , Índice de Massa Corporal , Peso Corporal , Criança , Feminino , Humanos , Masculino , Taxa de Depuração Metabólica , Oxirredução , Oxigênio/metabolismoRESUMO
The purpose of this study was to assess the validity of two common methods used to assess energy intake. A 3-day weighed dietary record and a dietary history were collected and compared with the total daily energy expenditure (TEE) assessed by the heart rate method in a group of 12 obese and 12 nonobese prepubertal children (mean age 9.3 +/- 1.1 years vs 9.3 +/- 0.4 years). The TEE value was higher in obese than in nonobese children (9.89 +/- 1.08 vs 8.13 +/- 1.39 MJ/day; p < 0.01). Energy intake assessed by the dietary record was significantly lower than TEE in the obese children (7.06 +/- 0.98 MJ/day; p < 0.001) but comparable to TEE in the nonobese children (8.03 +/- 0.99 MJ/day; p = not significant). Energy intake assessed by diet history was lower than TEE in the obese children (8.37 +/- 1.35 MJ/day, p < 0.05) but close to TEE in the nonobese children (8.64 +/- 1.54 MJ/day, p = not significant). These results suggest that obese children underreport food intake and that the dietary record and the diet history are not valid means of assessing energy intake in obese prepubertal children.
Assuntos
Registros de Dieta , Ingestão de Energia , Metabolismo Energético , Obesidade/metabolismo , Estudos de Casos e Controles , Criança , Feminino , Humanos , Masculino , Avaliação NutricionalRESUMO
We measured body composition and energy expenditure during walking and running on a treadmill in 40 prepubertal children: 23 obese children (9.3 +/- 1.1 years of age; 46 +/- 10 kg (mean +/- SD)) and 17 nonobese matched control children (9.2 +/- 0.6 years of age; 30 +/- 5 kg). Energy expenditure was assessed by indirect calorimetry with a standard open-circuit method. At the same speed of exercise, the energy expenditure was significantly (p < 0.01) greater in obese than in control children, in both boys and girls. Expressed per kilogram of body weight or per kilogram of fat-free mass, the energy expenditure was comparable in the two groups. Obese children had a significantly (p < 0.01) larger pulmonary ventilatory response to exercise than did control children. Heart rate was comparable in boys and girls combined but significantly higher (p < 0.05) in obese subjects, if boys and girls were analyzed separately. These data indicate that walking and running are energetically more expensive for obese children than for children of normal body weight. The knowledge of these energy costs could be useful in devising a physical activity program to be used in the treatment of obese children.
Assuntos
Metabolismo Energético , Obesidade/fisiopatologia , Corrida/fisiologia , Caminhada/fisiologia , Peso Corporal , Calorimetria , Criança , Teste de Esforço , Feminino , Frequência Cardíaca , Humanos , Masculino , Obesidade/metabolismo , Esforço Físico , Puberdade , Respiração , DescansoRESUMO
The resting metabolic rate (RMR) and body composition of 130 obese and nonobese prepubertal children, aged 6 to 10 years, were assessed by indirect calorimetry and skin-fold thickness, respectively. The mean (+/- SD) RMR was 4619 +/- 449 kJ.day-1 (164 +/- 31 kJ.kg body weight-1 x day-1) in the 62 boys and 4449 +/- 520 kJ.day-1 (147 +/- 32 kJ.kg body weight-1 x day-1) in the 68 girls. Fat-free mass was the best single predictor of RMR (R2 = 0.64; p < 0.001). Step-down multiple regression analysis, with independent variables such as age, gender, weight, and height, allowed several RMR predictive equations to be developed. An equation for boys is as follows: RMR (kJ.day-1) = 1287 + 28.6 x Weight(kg) + 23.6 x Height(cm) - 69.1 x Age(yr) (R2 = 0.58; p < 0.001). An equation for girls is as follows: RMR (kJ.day-1 = 1552 + 35.8 x Weight (kg) + 15.6 x Height (cm) - 36.3 x Age (yr) (R2 = 0.69; p < 0.001). Comparison between the measured RMR and that predicted by currently used formulas showed that most of these equations tended to overestimate the RMR of both genders, especially in overweight children.
Assuntos
Metabolismo Basal , Composição Corporal , Obesidade/metabolismo , Análise de Variância , Peso Corporal , Calorimetria Indireta , Criança , Feminino , Humanos , Masculino , Valores de Referência , Análise de Regressão , Caracteres Sexuais , Dobras CutâneasRESUMO
The increase in resting energy expenditure (REE) reported in patients with cystic fibrosis (CF) does not necessarily imply an increase in total energy expenditure (TEE). In this study REE was assessed with open-circuit indirect calorimetry, and free-living 24-hour TEE with the heart rate method. Thirteen patients with CF, aged 8 to 24 years, with adequate nutritional status and moderately decreased pulmonary function, were studied. They were compared with 13 healthy control subjects matched for gender, age, height, and nutritional status. Resting energy expenditure was higher in patients with CF (1512 +/- 88 kcal/day) than in control subjects (1339 +/- 76 kcal/day; p less than 0.01), whereas free-living 24-hour TEE (2345 +/- 127 kcal/day and 2358 +/- 256 kcal/day, respectively) and net mechanical work efficiency of walking on a treadmill (20.4 +/- 0.7% and 19.8 +/- 0.6%, respectively) were similar. Respiratory quotient was higher in patients with CF than in control subjects at rest (0.834 +/- 0.009 vs 0.797 +/- 0.008; p less than 0.05), and tended to remain so during physical exercise, indicating a higher contribution of carbohydrate oxidation to energy expenditure. We conclude that in free living conditions, patients with CF can compensate for their increase in REE by a reduction in spontaneous physical activities or other yet undefined mechanisms.
Assuntos
Metabolismo Basal/fisiologia , Fibrose Cística/metabolismo , Metabolismo Energético/fisiologia , Adolescente , Adulto , Criança , Fibrose Cística/sangue , Feminino , Frequência Cardíaca/fisiologia , Humanos , Masculino , Consumo de Oxigênio , Esforço Físico/fisiologiaRESUMO
Total energy expenditures and intakes were simultaneously assessed in 18 free-ranging lactating women (10 months postpartum) and compared to six similarly-sized, nonlactating, nonpregnant but multiparous women living in the same rural villages in the Guatemalan highlands. Energy intakes were estimated by the 24-hr recall method for each of 4 consecutive days. Energy expenditures were determined for 2 days by monitoring heart rate throughout the day and relating heart rate to oxygen consumption by individually-determined regression lines. The mean energy intake for the 4 consecutive days was estimated to be 1929 +/- 360 kcal/day (39.2 kcal/kg per day) for the lactating group; and 1876 +/- 404 kcal/day (38.3 kcal/kg per day) for the nonlactating group. The 2-day mean energy expenditures were estimated to be 2007 +/- 292 kcal/day for the lactating women (41.8 kcal/kg per day) and 1966 +/- 382 kcal/day for the lactating women (40.1 kcal/kg per day). The way of life of both groups was judged "moderately active" by 1973 FAO/WHO classifications. Most of the lactating women had been losing weight progressively during the past 6 months. Over the 10-week period prior to our measurnth) (P less than 0.01) than in the nonlactating group (-35 g/month) (ns). The high correlation (r = 0.87) between weight loss and the reduction in the sum of the three skinfolds suggested adipose tissue loss. There were no significant differences between the two groups in terms of daily energy intake, daily energy expenditure, the energy cost of specific activities throughout the day. The slope of the heart rate/oxygen consumption regressions suggest adequate cardiorespiratory fitness. This study suggests that the energy cost of lactation was met to a greater extent by fat loss than by either increased energy intake, reduced energy expenditure, or both.
PIP: Total energy expenditures and intakes were simultaneously assessed in 18 lactating women (10 months postpartum) and compared to 6 similarly-sized nonlactating, nonpregnant but multiparious women living in the same rural villag in the Guatemalan highlands. Energy intakes were estimated by the 24-hour recal method for each of 4 consecutive days. Energy expenditures were determined for 2 days by monitoring heart rate throughout the day and relating heart rate to oxygen consumption by individually-determined regression lines. The mean energy intake for the 4 consecutive days was estimated to be 1929 + or 360 kcal/day (39.2 kcal/kg/day) for the lactating group and 1876 + or - 404 kcal/day (38.3 kcal/kg/day) for the nonlactating group. The 2-day mean energy expenditures were estimated to be 2007 + or - 292 kcal/day for the lactating women (41.8 kcal/kg/day) and 1966 + or - 382 kcal/day for the nonlactating women (40.1 kcal/kg/day). The way of life of both groups was judged as moderately active by 1973 FAO/WHO classifications. Most of the lactating women had been losing weight progressively during the past 6 months. Over the 10-week period prior to our measurements, the mean weight loss was more than 10 times greater in the lactating group (-369 g/month) (P 0.01) than in the nonlactating group (-35 g/month) (ns). The high correlation (r=0.87) between weight loss and the reduction in the sum of 3 skinfolds suggested adipose tissue loss. There were n significant differences between the 2 groups in terms of daily energy intake; daily energy expenditure; energy cost of specific activities; or in the pattern of activites during the day. The slope of the heart rate/oxygen consumption regressions suggest adequate cardiorespiratory fitness. This study indicates that the energy cost of lactation was met to a greater extent by fat loss than by either increased energy intake, reduced expenditure, or both.