Changes in energy expenditure resulting from altered body weight.
Level 3 - non-randomized controlled study
non-randomized experimental cohort study with within-subject repeated measures across weight states
PubMed 7632212 · doi:10.1056/NEJM199503093321001
What was done
Researchers measured 24-hour total energy expenditure, resting energy expenditure, nonresting energy expenditure, and the thermic effect of feeding in 18 obese subjects and 23 subjects who had never been obese. Measurements were obtained at usual baseline body weight and compared with measurements after losing 10% to 20% of body weight by underfeeding or gaining 10% of body weight by overfeeding.
What was found
Maintenance of weight at 10% or more below baseline was associated with a mean (± SD) reduction in total energy expenditure of 6 ± 3 kcal/kg of fat-free mass/day in never-obese subjects (P < 0.001) and 8 ± 5 kcal/kg of fat-free mass/day in obese subjects (P < 0.001). Resting and nonresting energy expenditure each decreased by 3 to 4 kcal/kg fat-free mass/day in both groups. Conversely, maintaining a 10% weight gain increased total energy expenditure by 9 ± 7 kcal/kg fat-free mass/day in never-obese subjects (P < 0.001) and 8 ± 4 kcal/kg fat-free mass/day in obese subjects (P < 0.001), with nonresting energy expenditure increasing by approximately 8 to 9 kcal/kg fat-free mass/day and thermic effect of feeding increasing by 1 to 2 kcal/kg fat-free mass/day. These changes were not related to baseline adiposity or sex.
Why it matters
This study demonstrated that metabolic energy expenditure adjusts to oppose sustained weight loss or gain, offering a physiological mechanism for why long-term weight-loss maintenance is difficult.
Limits
The sample size was small (41 total participants). The abstract does not specify whether participants underwent both overfeeding and underfeeding, the sequence of interventions, the exact duration of weight-maintenance periods, or long-term outcomes beyond the experimental maintenance phases.
Cited by
- supports Losing 10% of body weight causes an average 15% decline in basal metabolic rate beyond what is expected from lost mass.
- partial Losing 10% of body weight can induce a 400 to 500 calorie decrease in non-exercise activity thermogenesis (NEAT) per day.