Long–term effects of caloric restriction on total and resting energy expenditure in healthy adults

Abstract

The effects of long‐term caloric restriction (CR) on resting metabolic rate (RMR) and total energy expenditure (TEE) in humans is uncertain. Objective To examine the effects of a 30% CR regimen on TEE and RMR. Methods One year randomized controlled trial of 30% CR in 29 healthy overweight adults (mean±SD, age 35±5y; BMI 27.5±1.5 kg/m2). All food was provided for 6 mo, and self‐administered for the next 6 mo. Outcomes included TEE, RMR, and body fat and fat free mass (FFM). Results Absolute values for RMR decreased during the intervention compared to baseline but measured RMR during CR was not significantly different from RMR predicted from body composition, and RMR changes over time assessed at 3, 6 and 12 mo were not statistically significant after accounting for decreases in body fat and FFM. TEE also decreased significantly with CR but at 12 mo there was a greater reduction in TEE than that anticipated due to the loss of FFM and fat mass (P=0.018). Conclusions This study found no evidence for long‐term metabolic adaptation to weight loss in assessments of RMR, but an adaptive reduction in TEE was observed, which may serve to protect the body against weight loss and contribute to weight regain.Support: NIH grants: NGA‐3U01‐AG20480& #H150001; USDA No. 58‐1950‐4‐401.