Evolution and obesity: resistance of obese-prone rats to a challenge of food restriction and wheel running.
The adaptive hypothesis that an obese-prone genotype confers a fitness advantage when challenged with food restriction and food-related locomotion was tested using a rat model. Juvenile (35-40 days) and adolescent (45-50 days) JCR:LA-cp rats, obese prone (cp/cp) and lean prone (+/?), were exposed to 1.5 h daily meals and 22.5 h of voluntary wheel running, a procedure that normally leads to self-starvation. Genotype had a dramatic effect on survival of rats when exposed to the challenge of food restriction and wheel running. Although similar in initial body weight, obese-prone juveniles survived twice as long, and ran three times as far, as their lean-prone counterparts. Biochemical measures indicated that young obese-prone animals maintained blood glucose and fat mass, whereas lean-prone rats depleted these energy reserves. Corticosterone concentration indicated that obese-prone juveniles exhibited a lower stress response to the survival challenge than lean-prone rats, possibly due to lower energy demands and greater energy reserves. Collectively, the findings support the hypothesis that an obese-prone genotype provides a fitness advantage when food supply is inadequate, but is deleterious during periods of food surfeit, such as the energy-rich food environment of prosperous and developing societies worldwide.
Pierce
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WD
Department of Sociology, University of Alberta, Edmonton, Alberta, Canada. dpierce@ualberta.ca
Diane
A
A
Heth
C D
CD
Russell
J C
JC
Proctor
S D
SD
D000222:Adaptation, Physiological; D000818:Animals; D003345:Corticosterone / Q000097:blood; D004435:Eating / Q000235:genetics / Q000502:physiology*; D004734:Energy Metabolism / Q000235:genetics / Q000502:physiology*; D005508:Food Deprivation / Q000502:physiology*; D005838:Genotype; D009765:Obesity / Q000235:genetics / Q000401:mortality / Q000503:physiopathology*; D010805:Physical Conditioning, Animal / Q000502:physiology*; D051381:Rats; D013851:Thinness / Q000235:genetics / Q000503:physiopathology
D003345:Corticosterone