Meal-induced thermogenesis in lean and obese prepubertal children.

The resting metabolic rate (RMR) and the thermic effect of a meal (TEM) were measured in a group of 16 prepubertal (8.8 +/- 0.3 y) obese children (43.6 +/- 9.2 kg) and compared with a group of 10 age-matched (8.6 +/- 0.4 y), normal-weight children (31.0 +/- 6.0 kg). The RMR was higher in the obese than in the control children (4971 +/- 485 vs 4519 +/- 326 kJ/d, P < 0.05); after the RMR was adjusted for the effect of fat-free mass (FFM) the values were not significantly different (4887 +/- 389 vs 4686 +/- 389 kJ/d). The thermic response to a liquid mixed meal, expressed as a percentage of the energy content of the meal, was significantly lower in obese than in control children (4.4 +/- 1.2% vs 5.9 +/- 1.7%, P < 0.05). The blunted TEM shown by the obese children could favor weight gain and suggests that the defect in thermogenesis reported in certain obese adults may have already originated early in life.

[Energy metabolism at rest and the respiratory quotient in obese and normal-weight prepubertal children]. / Metabolismo energetico a riposo e quoziente respiratorio in bambini prepuberi obesi e normopeso.

The resting metabolic rate (RMR) was measured in obese (n. 14) and normo-weight (n. 14) pre-pubertal children using indirect calorimetry: correlations between RMR and anthropometric and metabolic parameters were also assessed in order to identify the existence of a causal relationship between the reduction of the RMR and the onset of obesity in children. RMR was expressed as an absolute value and appeared to be higher in obese subjects in comparison to controls (5138 +/- 498 kJ/d vs 4443 +/- 481, p less than 0.0001). If corrected for Kg of fat free mass (FFM), the anthropometric variable which accounts for the major (75%) variations of RMR, resting metabolism in obese subjects was lower than that in normal weight controls (173.2 +/- 20.1 kJ/kg FFM/d vs 189.9 +/- 17.6, p less than 0.05). The lower percentage of metabolic active organs which make up the lean body mass in FFM (brain, heart, liver and kidneys) and the absence of a defect in resting thermogenesis in the obese child could nevertheless explain the reduction of RMR/kg FFM observed in the study.

Periventricular heterotopia in fragile X syndrome.

The authors describe two unrelated individuals with fragile X syndrome (FXS) due to marked expansion and instability of the CGG trinucleotide repeats within the fragile X mental retardation 1 gene (FMR1) and periventricular heterotopia (PH). This observation suggests that the FMR1 gene is involved in neuronal migration and that abnormal neuronal migration, even beyond the resolution of MRI, contributes to the neurologic phenotype of FXS.

Meal-induced thermogenesis in obese children with or without familial history of obesity.

Resting metabolic rate (RMR) and the thermic effect of a meal (TEM) were measured in a group of 26 prepubertal children divided into three groups: (1) children with both parents obese (n = 8, group OB2); (2) children with no obese parents and without familial history of obesity (n = 8, OB0); and (3) normal body weight children (n = 10, C). Average RMR was similar in OB2 and OB0 children (4785 +/- 274 kJ/day vs 5091 +/- 543 kJ/day), but higher (P < 0.05) than in controls (4519 +/- 322 kJ/day). Adjusted for fat-free mass (FFM) mean RMRs were comparable in the three groups of children (4891 +/- 451 kJ/day vs 5031 +/- 451 kJ/day vs 4686 +/- 451 kJ/day in OB2, OB0, and C, respectively). The thermic response to the mixed meal was similar in OB2, OB0 and C groups. The TEM calculated as the percentage of RMR was lower (P < 0.05) in obese than in control children: 10.2% +/- 3.1% vs 10.9% +/- 4.3% vs 14.0% +/- 4.3% in OB2, OB0, and C, respectively. The similar RMR as absolute value as well as adjusted for FFM, and the comparable thermic effect of food in the obese children with or without familial history of obesity, failed to support the view that family history of obesity can greatly influence the RMR and the TEM of the obese child with obese parents.

Maximal aerobic power during running and cycling in obese and non-obese children.

The maximal aerobic capacity while running and cycling was measured in 22 prepubertal children (mean age +/- SD 9.5 +/- 0.8 years): 14 obese (47.3 +/- 10 kg) and 8 non-obese (31.1 +/- 6.1 kg). Oxygen consumption (VO2) and carbon dioxide production were measured by an open circuit method. Steady state VO2 was determined at different levels of exercise up to the maximal power on the cycloergometer (92 W in obese and 77 W in non-obese subjects) and up to the maximal running speed on the treadmill at a 2% slope (8.3 km/h in obese and 9.0 km/h in lean children). Expressed in absolute values, the VO2max in obese children was significantly higher than in controls (1.55 +/- 0.29 l/min versus 1.23 +/- 0.22 l/min, p < 0.05) for the treadmill test and comparable in the two groups (1.4 +/- 0.2 l/min versus 1.16 +/- 0.2 l/min, ns) for the cycloergometer test. When VO2max was expressed per kg fat free mass, the difference between the two groups disappeared for both tests. These data suggest that obese children had no limitation of maximal aerobic power. Therefore, the magnitude of the workload prescribed when a physical activity program is intended for the therapy of childhood obesity, it should be designed to increase caloric output rather than to improve cardiorespiratory fitness.

Basal energy expenditure in obese and normal weight schoolchildren.

The present study was performed using indirect calorimetry to test the hypothesis of a reduction of the basal energy expenditure in obese prepubertal children. The obese and control children studied were comparable regarding age, height and fat-free mass (FFM). Total weight and body fat percentage were significantly greater in the obese children. Plasma insulin and glucagon concentrations were significantly higher in obese than in control children. In the two groups of children the basal metabolic rates (BMRs) were comparable in both absolute values and values adjusted for FFM, age and gender utilizing the multiple regression analysis. The most important variable to predict BMR was FFM, followed by age. BMR was significantly correlated with FFM, both for obese and control children, and also when the two groups were combined. In conclusion, our data do not support the idea that a child's obesity is maintained by increased metabolic efficiency at least in basal conditions.

Resting metabolic rate in six- to ten-year-old obese and nonobese children.

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.