Lower core body temperature and greater body fat are components of a human thrifty phenotype.
In small studies, a thrifty human phenotype, defined by a greater 24-hour energy expenditure (EE) decrease with fasting, is associated with less weight loss during caloric restriction. In rodents, models of diet-induced obesity often have a phenotype including a reduced EE and decreased core body temperature. We assessed whether a thrifty human phenotype associates with differences in core body temperature or body composition.



Data for this cross-sectional analysis were obtained from 77 individuals participating in one of two normal physiology studies while housed on our clinical research unit. Twenty-four-hour EE using a whole-room indirect calorimeter and 24-h core body temperature were measured during 24 h each of fasting and 200% overfeeding with a diet consisting of 50% carbohydrates, 20% protein and 30% fat. Body composition was measured by dual X-ray absorptiometry. To account for the effects of body size on EE, changes in EE were expressed as a percentage change from 24-hour EE (%EE) during energy balance.



A greater %EE decrease with fasting correlated with a smaller %EE increase with overfeeding (r=0.27, P=0.02). The %EE decrease with fasting was associated with both fat mass and abdominal fat mass, even after accounting for covariates (β=-0.16 (95% CI: -0.26, -0.06) %EE per kg fat mass, P=0.003; β=-0.0004 (-0.0007, -0.00004) %EE kg(-1) abdominal fat mass, P=0.03). In men, a greater %EE decrease in response to fasting was associated with a lower 24- h core body temperature, even after adjusting for covariates (β=1.43 (0.72, 2.15) %EE per 0.1 °C, P=0.0003).



Thrifty individuals, as defined by a larger EE decrease with fasting, were more likely to have greater overall and abdominal adiposity as well as lower core body temperature consistent with a more efficient metabolism.
Department of Health and Human Services, Obesity and Diabetes Clinical Research Section, Phoenix Epidemiology and Clinical Research Branch National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Phoenix, AZ, USA.|Department of Diagnostic and Interventional Radiology, University Leipzig, Leipzig, Germany.
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Reinhardt
Department of Health and Human Services, Obesity and Diabetes Clinical Research Section, Phoenix Epidemiology and Clinical Research Branch National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Phoenix, AZ, USA.|Department of Geriatrics and Aging Research, University Hospital Zurich, Zurich, Switzerland.
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Schlögl
Department of Health and Human Services, Obesity and Diabetes Clinical Research Section, Phoenix Epidemiology and Clinical Research Branch National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Phoenix, AZ, USA.
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Bonfiglio
Department of Health and Human Services, Obesity and Diabetes Clinical Research Section, Phoenix Epidemiology and Clinical Research Branch National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Phoenix, AZ, USA.
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Votruba
Department of Health and Human Services, Obesity and Diabetes Clinical Research Section, Phoenix Epidemiology and Clinical Research Branch National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Phoenix, AZ, USA.
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Krakoff
Department of Health and Human Services, Obesity and Diabetes Clinical Research Section, Phoenix Epidemiology and Clinical Research Branch National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Phoenix, AZ, USA.
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Thearle
D015502:Absorptiometry, Photon; D000273:Adipose Tissue; D050154:Adiposity / Q000502:physiology*; D000328:Adult; D001130:Arizona; D001823:Body Composition / Q000502:physiology*; D001831:Body Temperature / Q000502:physiology*; D031204:Caloric Restriction; D003430:Cross-Sectional Studies; D004734:Energy Metabolism / Q000502:physiology*; D005215:Fasting / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D010641:Phenotype; D015203:Reproducibility of Results; D022722:Thermogenesis