Body size and human energy requirements: Reduced mass-specific total energy expenditure in tall adults

Mammalian resting energy expenditure (REE) increases as approximately weight(0.75) while mass-specific REE scales as approximately weight(-0.25). Energy needs for replacing resting losses are thus less relative to weight (W) in large compared with small mammals, a classic observation with biological implications. Human weight scales as approximately height(2) and tall adults thus have a greater weight than their short counterparts. However, it remains unknown if mass-specific energy requirements are less in tall adults; allometric models linking total energy expenditure (TEE) and weight with height (H) are lacking. We tested the hypothesis that mass-specific energy requirements scale inversely to height in adults by evaluating TEE (doubly labeled water) data collected by the National Academy of Sciences. Activity energy expenditure (AEE) was calculated from TEE, REE (indirect calorimetry), and estimated diet-induced energy expenditure. Main analyses focused on nonmorbidly obese subjects < or =50 yrs of age with non-negative AEE values (n = 404), although results were directionally similar for all samples. Allometric models, including age as a covariate, revealed significantly (P < 0.05) greater REE, AEE, and TEE as a function of height (range H(1.5-1.7)) in both men and women. TEE/W scaled negatively to height ( approximately H(-0.7), P < 0.01) with predicted mass-specific TEE (kcal/kg/d) at +/-2 SD for US height lower in tall compared with short men (40.3 vs. 46.5) and women (37.7 vs. 42.7). REE/W also scaled negatively to height in men (P < 0.001) and women (P < 0.01). Results were generally robust across several different analytic strategies. These observations reveal previously unforeseen associations between human stature and energy requirements that have implications for modeling efforts and provide new links to mammalian biology as a whole.