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 São Paulo, Brazil. Twenty-eight were stunted (height-for-age z score < Ϫ1.5) and 30 had similar weight-for-height but normal height (height-for-age z score > Ϫ1.5). 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 atrisk populations. This finding may help explain recent increases in body fatness and the prevalence of obesity among stunted adults and adolescents in developing countries.Am J Clin Nutr 2000;72:702-7.

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Previous studies by our group and others have suggested that nutritional stunting may increase the risk of obesity. To investigate mechanisms that could explain a link between stunting and obesity, a 22-mo follow-up study was conducted in two groups of shantytowns school girls (7-11 y old) in São Paulo, Brazil. One group (n = 15) had mild stunting (defined using a cutoff of -1.4 Z-scores of height-for-age) but normal weight-for-height; the control group (n = 15) had normal weight and height. Similar energy intake, dietary macronutrient composition and energy expenditure were observed in the two groups. Both groups showed comparable levels of IGF-1 that were below the normal range. A significant and positive association between baseline IGF-1 and the change in height-for-age during follow-up was found in all subjects combined (P = 0.044). A significant association was found between the baseline percentage of dietary energy supplied by fat and the gain in weight-for-height during follow-up in girls with mild stunting (P = 0.048), but not in the nonstunted control girls (P = 0.245); however, the slopes of these relationships were not significantly different. This study raises the question of whether a diet high in fat may increase the susceptibility to excess body fat gain in children who are mildly stunted. Further studies are need to explore this issue and to examine the possible etiological role of low levels of IGF-1.