Lower energy expenditure predicts long-term increases in weight and fat mass

Abstract

Context: The relevance of the contribution of energy expenditure (EE) and substrate oxidation to weight change has not been fully confirmed.

Objective: The objective of the study was to determine whether metabolic parameters measured in a whole room indirect calorimeter are predictive of long-term body weight change.

Setting: The study was conducted at a clinical research unit in Phoenix, Arizona, from 1985 to 2005.

Participants: A total of 612 healthy subjects (384 males and 228 females; aged 29.5 ± 8.1 years; body mass index 33.0 ± 8.7 kg/m(2); percent body fat 30.9 ± 9.6%), including 422 Native Americans and 190 whites. Follow-up data were available for 292 Native Americans with a median follow-up time of 6.7 years (interquartile range 3.9-10.5).

Main outcome measures: Twenty-four-hour EE, sleeping metabolic rate, daily (fed) and sleeping (fasting) respiratory quotient, and carbohydrate and fat oxidation rates were measured during a 24-hour respiratory chamber. Body composition was assessed by underwater weighing or dual-energy x-ray absorptiometry.

Results: After accounting for demographic and body composition measures, the remaining variance of 24-hour EE was inversely related to the rate of weight change (ρ = -0.158, P = .007) and fat mass change (ρ = -0.179, P = .012), such that 100 kcal below the expected 24-hour EE corresponded to 0.2 kg/y weight gain, of which 0.1 kg/y was fat mass. Deviations from the predicted values of the sleeping metabolic rate (ρ = -0.121, P = .039) and fed respiratory quotient (ρ = 0.119, P = .042) were also associated with future weight change, whereas the fat oxidation rate was inversely associated with weight change in men (ρ = -0.174, P = .024) but not in women (ρ = 0.018, P = .853).

Conclusions: Measures of energy expenditure and substrate oxidation are predictors of long-term weight change, indicating a small but significant role for reduced metabolic rate in weight gain.

Figure 1.

Lower-than-expected 24-hour EE predicts rates of future body weight gain and FM gain. Inverse relationships between 24-hour EE (adjusted for age, gender, ethnicity, FFM, and FM; ρ = −.158, P = .007) vs the rate of percent weight change in 292 subjects after a median follow-up time of 6.7 years (IQR 3.9–10.5, left panel) and vs rate of percent fat mass change (ρ = −.179, P = .012) in 215 subjects after a median follow-up time of 7.2 years (IQR 4.4–11.1, right panel). Both the RoWC and FM change on the y-axis are reported in a safe-logarithmic scale, eg, sign(RoWC)·log₁₀[1 + abs(RoWC)], which can handle negative and zero values.