Energy metabolism after 2 y of energy restriction: the biosphere 2 experiment

Am J Clin Nutr. 2000 Oct;72(4):946-53. doi: 10.1093/ajcn/72.4.946.


Background: An adaptive decrease in energy expenditure (EE) in response to 6 mo of severely restricted energy intake was shown in a classic semistarvation study-the Minnesota experiment.

Objective: Our objective was to examine whether such adaptation also occurs in response to less severe but sustained energy restriction.

Design: Body composition, 1-wk total EE (TEE), 24-h sedentary EE, and spontaneous physical activity were measured in 8 healthy subjects (4 men and 4 women) at the end of a 2-y confinement inside Biosphere 2. Unexpectedly, the food supply was markedly restricted during most of the confinement and all subjects experienced a marked, sustained weight loss (9.1 +/- 6.6 kg; P: < 0.001) from the low-energy (7000-11000 kJ/d), low-fat (9% of energy), but nutrient-dense, diet they consumed.

Results: The TEE inside Biosphere 2, assessed 3 wk before exit, averaged 10700 +/- 560 kJ/d (n = 8). Within 1 wk after exit, the adjusted 24-h EE and spontaneous physical activity were lower in the biospherians (n = 5) than in 152 control subjects (6% and 45%, respectively; both P: < 0.01). Six months after exit and return to an ad libitum diet, body weight had increased to preentry levels; however, adjusted 24-h EE and spontaneous physical activity were still significantly lower than in control subjects.

Conclusions: In lean humans, an adaptive decrease in EE appears to occur not only in states of life-threatening undernutrition, but also in response to less severe energy restriction sustained over several years.

MeSH terms

  • Adult
  • Aged
  • Basal Metabolism
  • Body Composition
  • Calorimetry, Indirect
  • Diet*
  • Ecological Systems, Closed
  • Energy Intake / physiology*
  • Energy Metabolism / physiology*
  • Exercise / physiology
  • Female
  • Humans
  • Linear Models
  • Male
  • Oxygen Consumption
  • Radioimmunoassay
  • Regression Analysis
  • Thyrotropin / blood
  • Thyroxine / blood
  • Triiodothyronine / blood
  • Weight Loss


  • Triiodothyronine
  • Thyrotropin
  • Thyroxine