Do adaptive changes in metabolic rate favor weight regain in weight-reduced individuals? An examination of the set-point theory.
BACKGROUND
Obese persons generally regain lost weight, suggesting that adaptive metabolic changes favor return to a preset weight.


OBJECTIVE
Our objective was to determine whether adaptive changes in resting metabolic rate (RMR) and thyroid hormones occur in weight-reduced persons, predisposing them to long-term weight gain.


METHODS
Twenty-four overweight, postmenopausal women were studied at a clinical research center in four 10-d study phases: the overweight state (phase 1, energy balance; phase 2, 3350 kJ/d) and after reduction to a normal-weight state (phase 3, 3350 kJ/d; phase 4, energy balance). Weight-reduced women were matched with 24 never-overweight control subjects. After each study phase, assessments included RMR (by indirect calorimetry), body composition (by hydrostatic weighing), serum triiodothyronine (T(3)), and reverse T(3) (rT(3)). Body weight was measured 4 y later, without intervention.


RESULTS
Body composition-adjusted RMR and T(3):rT(3) fell during acute (phase 2) and chronic (phase 3) energy restriction (P: < 0.01), but returned to baseline in the normal-weight, energy-balanced state (phase 4; mean weight loss: 12.9 +/- 2.0 kg). RMR among weight-reduced women (4771 +/- 414 kJ/d) was not significantly different from that in control subjects (4955 +/- 414 kJ/d; P: = 0.14), and lower RMR did not predict greater 4-y weight regain (r = 0.27, NS).


CONCLUSIONS
Energy restriction produces a transient hypothyroid-hypometabolic state that normalizes on return to energy-balanced conditions. Failure to establish energy balance after weight loss gives the misleading impression that weight-reduced persons are energy conservative and predisposed to weight regain. Our findings do not provide evidence in support of adaptive metabolic changes as an explanation for the tendency of weight-reduced persons to regain weight.
Weinsier
R L
RL
Departments of Nutrition Sciences and Human Studies, the General Clinical Research Center, University of Alabama at Birmingham, and the Mayo Clinic, Rochester, MN, USA. weinsier@shrp.uab.edu
Nagy
T R
TR
Hunter
G R
GR
Darnell
B E
BE
Hensrud
D D
DD
Weiss
H L
HL
D000368:Aged; D001481:Basal Metabolism; D001823:Body Composition; D015992:Body Mass Index; D002153:Calorimetry, Indirect; D004038:Diet, Reducing; D002149:Energy Intake; D005260:Female; D006801:Humans; D007700:Kinetics; D008875:Middle Aged; D008954:Models, Biological; D009765:Obesity / Q000178:diet therapy / Q000235:genetics / Q000378:metabolism; D017698:Postmenopause; D014284:Triiodothyronine / Q000097:blood; D014285:Triiodothyronine, Reverse / Q000097:blood; D015430:Weight Gain; D015431:Weight Loss
D014284:Triiodothyronine; D014285:Triiodothyronine, Reverse