title: Changes in energy metabolism in response to 48 h of overfeeding and fasting in Caucasians and Pima Indians.
abstract: OBJECTIVE
  Differences in the metabolic response to overfeeding and starvation may confer susceptibility or resistance to obesity in humans. To further examine this hypothesis, we assessed the changes in 24 h energy metabolism in response to short-term overfeeding and fasting in Caucasians (C) and Pima Indians (I), a population with a very high propensity for obesity.
  
  
  METHODS
  We measured the changes in 24 h energy expenditure (24 -EE) and 24 h respiratory quotient (24-RQ) in response to 48 h of mixed diet overfeeding (100% above energy requirements) and fasting in a whole body respiratory chamber in 14 male subjects (7 C/7 I, age 30+/-6 y, mean+/-s.d.). Results were compared to a 24 h measurement under eucaloric conditions.
  
  
  RESULTS
  Mean 24-EE increased in response to overfeeding and decreased in response to fasting (all changes P<0.01), with no differences between C (+9.1% and -9.1%) and I (+8.6% and -9.6%). Similarly, mean 24-RQ increased/decreased in response to overfeeding/fasting, respectively (all changes P<0.01), again with no differences between C (+0.06 and -0.05) and I (+0.05 and -0.05). The changes in 24-EE in response to overfeeding and fasting were positively correlated (r=0.70, P<0.01), whereas those in 24-RQ were not (r=0.40, NS).
  
  
  CONCLUSIONS
  Pima Indians do not appear to have an impaired metabolic response to short-term overfeeding and fasting that could explain their propensity for obesity. Individuals with a large increase in energy expenditure in response to overfeeding appear to have a small decrease in energy expenditure in response to starvation (spendthrift phenotype) and vice versa (thrifty phenotype).
authors.affiliation: Clinical Diabetes and Nutrition Section, NIDDK, National Institutes of Health, Phoenix, Arizona 85016, USA. cweyer@phx.niddk.nih.gov
authors.forename: C
authors.initials: C
authors.lastname: Weyer
authors.forename: B
authors.initials: B
authors.lastname: Vozarova
authors.forename: E
authors.initials: E
authors.lastname: Ravussin
authors.forename: P A
authors.initials: PA
authors.lastname: Tataranni
mesh_terms: D000328:Adult; D001130:Arizona; D044466:Asian People / Q000235:genetics*; D001481:Basal Metabolism / Q000235:genetics; D004435:Eating / Q000502:physiology*; D004734:Energy Metabolism / Q000235:genetics*; D005215:Fasting / Q000502:physiology; D006801:Humans; D007198:Indians, North American / Q000235:genetics*; D008297:Male; D009765:Obesity / Q000209:etiology* / Q000235:genetics; D010101:Oxygen Consumption / Q000235:genetics; D013997:Time Factors; D044465:White People / Q000235:genetics*