Body weight gain in free-living Pima Indians: effect of energy intake vs expenditure.

Pennington Biomedical Research Center, Baton Rouge, LA, USABACKGROUND: Obesity results from a chronic imbalance between energy intake and energy expenditure. However, experi-mental evidence of the relative contribution of interindividual differences in energy intake and expenditure (resting or due tophysical activity) to weight gain is limited.OBJECTIVE: To assess prospectively the association between baseline measurements of daily energy metabolism and weightchanges by studying free-living adult Pima Indians, one of the most obese populations in the world.DESIGN: A study of the pathogenesis of obesity in the Pima Indians living in Southwestern Arizona. The participants were 92nondiabetic Pima Indians (64M/28F, 35712y, 3579% body fat; mean7s.d.). At baseline, free-living daily energy metabolismwas assessed by doubly labeled water and resting metabolic rate (RMR) by indirect calorimetry. Data on changes in body weight(5.876.5kg) over a follow-up period of 473y were available in 74 (49M/25F) of the 92 subjects.RESULTS: The baseline calculated total energy intake (r¼0.25, P¼0.028) and RMR (r¼ 0.28, P¼0.016) were significantlyassociated with changes in body weight. The baseline energy expenditure due to physical activity was not associated withchanges in body weight.CONCLUSION: Using state-of-the-art methods to assess energy intake and expenditure in free-living conditions, we show forthe first time that the baseline calculated total energy intake is a determinant of changes in body weight in Pima Indians. Thesedata also confirm that a low RMR is a risk factor for weight gain in this population.International Journal of Obesity (2003) 27, 1578–1583. doi:10.1038/sj.ijo.0802469Published online 16 September 2003Keywords: risk factor; indirect calorimetry; doubly labelled water; energy expenditure; physical activity