Determinants of total daily energy expenditure: variability in physical activity

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Abstract
Excessive energy intake and/or reduced total daily energy expenditure (TEE) causes obesity. To determine the relationship between obesity and TEE in an obesity-prone population, we measured TEE, 24-h sedentary energy expenditure (SEDEE), and basal metabolic rate (BMR) in 30 Pima Indian men (83.6 ± 20.0 kg and 31 ± 9% fat) by the doubly labeled water method and a respiratory chamber. The energy expenditure for physical activity (EEACT) was calculated as TEE - (BMR + 0.1 TEE), where 10% of TEE is an estimate of the thermic effect of food. Fat-free mass was the best single determinant (P < 0.01) of TEE, explaining 48% of its variance. TEE, SEDEE, BMR, and EEACT were 12 010 ± 2292, 9945 ± 1559, 7677 ± 1901, and 3297 ± 1732 kJ/d, respectively. Because EEACT is dependent on body weight, EEACT/kg body wt (41.7 ± 23.2 kJ · d−1 · kg−1) and TEE/(BMR + 0.1 TEE) (1.39 ± 0.22) were used as indexes of the level of physical activity. Both indexes correlated negatively with percent body fat (r = −0.56, P < 0.01 and r = −0.42, P < 0.03, respectively). These results suggest that obesity is associated with lower levels of physical activity.