Specific Metabolic Rate Predicts Future Weight Change: Racial/Ethnic Differences in Mass-independent Energy Expenditure

Objective: We evaluated interindividual differences in adjusted energy expenditure (EE) during 24 h of carefully controlled energy balance conditions in an ethnically diverse cohort and tested whether the relationship between adjusted EE and free-living weight change at 1 year differed by race/ethnicity. Methods: Healthy individuals (n=120: 20 Blacks, 37 Whites, 46 Indigenous Americans, 17 Hispanics) had 24-h EE measured in a whole-room indirect calorimeter during eucaloric conditions and adjusted for body composition by DXA. Results: On average, adjusted 24-h EE (adj24hEE) was ~335 kJ/day lower in Blacks, reflecting a 20% lower metabolic rate per kg of fat free mass compared to other ethnic groups. Blacks self-reported lower mean perceived hunger, dietary disinhibition, and perceived stress. Among fifty-six individuals whose free-living weight change was assessed at 1 year, a 1 MJ/day higher adj24hEE at baseline predicted a mean weight gain of 3.6 kg only in races/ethnicities other than Blacks, whereas adj24hEE tended to be inversely associated with 1-year weight change in Blacks (race/ethnicity interaction p=0.02). Conclusions: Relative metabolic rate differs between races/ethnicities and differentially predicts future weight change. For individuals who do not self-identify as Black, relatively higher metabolic demands during sedentary conditions may drive energy sensing-mediated overeating and ultimately weight gain.