Increasing energy flux to decrease the biological drive toward weight regain after weight loss – A proof-of-concept pilot study

Summary Objective Weight loss induces compensatory biological adjustments that increase hunger and decrease resting metabolic rate (RMR), which increase propensity for weight regain. In non-obese adults high levels of physical activity coupled with high energy intake (high energy flux) are associated with higher RMR and reduced hunger. We tested the possibility that a high flux state attenuates the increase in hunger and the decrease in RMR characteristic of diet-induced weight loss. Methods Six obese adults [age (mean ± SE) = 42 ± 12 y; body mass index (BMI) = 35.7 ± 3.7 kg/m2 ] underwent measures of RMR, the thermic effect of a meal (TEM), and fasting and postprandial measures of hunger and fullness as well as plasma glucose and insulin. Following weight loss, subjects completed two 5-day conditions of energy balance in random order—Low Flux (LF): sedentary with energy intake (EI) = RMR (kcal/d) × 1.35; and High Flux (HF): net exercise energy cost of ∼500 kcal/d and EI = RMR (kcal/d) × 1.7. RMR was measured daily for each flux condition. The morning following each of the respective experimentally controlled HF and LF conditions (flux day 5), they underwent the same pre-weight loss tests and also reported their perceptions of hunger and fullness during the previous four days of HF and LF, respectively. Results Average daily RMR was higher during HF (1926 ± 138 kcal/day) compared to LF (1847 ± 126 kcal/day; P