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

• Published in: The American journal of clinical nutrition Vol. 72; no. 4; pp. 946 - 953
• Main Authors: WEYER, Christian, WALFORD, Roy L, HARPER, Inge T, MILNER, Mike, MACCALLUM, Taber, TATARANNI, P. Antonio, RAVUSSIN, Eric
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Society for Clinical Nutrition 01.10.2000; American Society for Clinical Nutrition, Inc
• Subjects: Adult; Aged; Basal Metabolism; Biological and medical sciences; Body Composition; Calorimetry, Indirect; Diet; Ecological Systems, Closed; Energy Intake - physiology; Energy Metabolism - physiology; Exercise - physiology; Feeding. Feeding behavior; Female; Fundamental and applied biological sciences. Psychology; Humans; Linear Models; Male; Metabolism; Nutrition; Oxygen Consumption; Radioimmunoassay; Regression Analysis; Space life sciences; Thyrotropin - blood; Thyroxine - blood; Triiodothyronine - blood; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Weight Loss; Physical exercise; Human; Energy metabolism; Senescence; Body weight; Environmental factor; Corporal biometry; Body composition; Feeding; Energetic cost; Biosphere; Adaptation; Low calorie diet
• ISSN: 0002-9165; 1938-3207
• DOI: 10.1093/ajcn/72.4.946

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