Daily energy expenditure in Mexican and USA Pima Indians: low physical activity as a possible cause of obesity

BACKGROUND: Obesity is caused by an imbalance between energy intake and ene rgy expenditure. However, it is unknown whether increased physical activity protects susceptible populations against the development of obesity and ty pe 2 diabetes. OBJECTIVE: To investigate the potential protective role of environment and physical activity against obesity by measuring total energy expenditure in Mexican and USA Pima Indians. METHODS: We compared the physical activity level of 40 (17 female and 23 ma le; 37 +/- 11 y, 66 +/- 13 kg) Mexican Pima Indians from a remote, mountain ous area of Northwest Mexico, with 40 age-and-sex matched (17 female and 23 male; 37 +/- 12 y, 93 +/- 22 kg) Pima Indians from the Gila River Indian C ommunity in Arizona, USA. We measured total energy expenditure (TEE) by dou bly labeled water and calculated physical activity by different methods: ph ysical activity level (PAL) as the ratio of TEE on resting metabolic rate ( RMR), TEE adjusted for RMR by linear regression, activity energy expenditur e adjusted for body weight (AEE), and activity questionnaire. RESULTS: Physical activity was higher in Mexican Pima Indians when compared with USA Pima Indians as assessed by PAL (1.97 +/- 0.34 vs 1.57 +/- 0.16, P < 0.0001), TEE adjusted for RMR (3289 +/- 454 vs 2671 +/- 454 kcal/day, P < 0.0001) and AEE adjusted for body weight (1243 +/- 415 vs 711 +/- 415 kc al/day, P < 0.0001). Questionnaires revealed more time spent on occupationa l activities among Mexican Pima compared with USA Pima (23.9 +/- 13.3 vs 12 .6 +/- 13.9h/week, P < 0.001). CONCLUSION: These data support a significant role for physical activity in the prevention of obesity in genetically susceptible populations.