title: Is propensity to obesity associated with the diurnal pattern of core body temperature?
abstract: BACKGROUND
  Obesity affects more than half a billion people worldwide, but the underlying causes remain unresolved. It has been proposed that propensity to obesity may be associated with differences between individuals in metabolic efficiency and in the energy used for homeothermy. It has also been suggested that obese-prone individuals differ in their responsiveness to circadian rhythms. We investigated both these hypotheses by measuring the core body temperature at regular and frequent intervals over a diurnal cycle, using indigestible temperature loggers in two breeds of canines known to differ in propensity to obesity, but prior to divergence in fatness.
  
  
  METHODS
  Greyhounds (obesity-resistant) and Labradors (obesity-prone) were fed indigestible temperature loggers. Gastrointestinal temperature was recorded at 10-min intervals for the period of transit of the logger. Diet, body condition score, activity level and environment were similar for both groups. Energy digestibility was also measured.
  
  
  RESULTS
  The mean core body temperature in obesity-resistant dogs (38.27 °C) was slightly higher (P<0.001) than in obesity-prone dogs (38.18 °C) and the former had a greater variation (P<0.001) in 24h circadian core temperature. There were no differences in diet digestibility.
  
  
  CONCLUSIONS
  Canines differing in propensity to obesity, but prior to its onset, differed little in mean core temperature, supporting similar findings in already-obese and lean humans. Obese-prone dogs were less variable in daily core temperature fluctuations, suggestive of a degree of circadian decoupling.
authors.affiliation: School of Animal and Veterinary Sciences, The University of Adelaide, Roseworthy, South Australia, Australia.
authors.forename: P I
authors.initials: PI
authors.lastname: Hynd
authors.affiliation: School of Animal and Veterinary Sciences, The University of Adelaide, Roseworthy, South Australia, Australia.
authors.forename: V H
authors.initials: VH
authors.lastname: Czerwinski
authors.affiliation: School of Animal and Veterinary Sciences, The University of Adelaide, Roseworthy, South Australia, Australia.
authors.forename: T J
authors.initials: TJ
authors.lastname: McWhorter
mesh_terms: D000818:Animals; D001481:Basal Metabolism / Q000235:genetics; D001831:Body Temperature / Q000235:genetics; D001833:Body Temperature Regulation; D002940:Circadian Rhythm; D004032:Diet; D004195:Disease Models, Animal; D004198:Disease Susceptibility; D004285:Dogs; D004734:Energy Metabolism; D024821:Metabolic Syndrome / Q000235:genetics / Q000378:metabolism*; D009765:Obesity / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology*