Objective: Epidemiologic studies suggest that Native Americans, including the Mohawk people, have a high prevalence of obesity, diabetes, and cardiovascular risk. However, current information on alterations in related variables such as energy metabolism and body composition in Native Americans is almost exclusively limited to already obese Pima adults living in the Southwest. The aim of this study was to characterize energy metabolism and body composition in young Mohawk children (17 girls, 11 boys; aged 4 to 7 years) as compared to Caucasian children (36 girls, 34 boys; aged 4 to 7 years). Total energy expenditure was measured by doubly labeled water, postprandial resting energy expenditure by indirect calorimetry, and activity energy expenditure was derived from the difference between total and resting energy expenditure. Fat and fat free mass were estimated from bioelectrical resistance, and body fat distribution was estimated from skinfolds and circumferences.
Results: There were no significant effects of ethnic background or sex on body weight, height, or body mass index. Fat free mass was significantly higher in boys and fat mass was significantly higher in girls, with no effect of ethnic background. Chest skinfold thickness, the ratio of trunk skinfolds:extremity skinfolds, and the waist:hip ratio were significantly higher in Mohawk children by 2.5 mm, 0.09 units, and 0.03 units, respectively, independent of sex and fat mass. Total energy expenditure was significantly higher in Mohawk children compared to Caucasian (100 kcal/day in girls, 150 kcal/day in boys), independent of fat free mass and sex, due to a significantly higher physical activity-related energy expenditure.
Conclusion: These data suggest that: 1) body fat is more centrally distributed in Mohawk relative to Caucasian children, and this effect is independent of sex and body fat content; 2) Mohawk children have a greater total energy expenditure than Caucasian children, independent of fat free mass, due to greater physical activity-related energy expenditure.