Fatness and fitness: exposing the logic of evolutionary explanations for obesity

Andrew D Higginson, John M McNamara, Alasdair I Houston

Research output: Contribution to journalArticle (Academic Journal)peer-review

30 Citations (Scopus)
299 Downloads (Pure)


To explore the logic of evolutionary explanations of obesity we modelled food consumption in an animal that minimizes mortality (starvation plus predation) by switching between activities that differ in energy gain and predation. We show that if switching does not incur extra predation risk, the animal should have a single threshold level of reserves above which it performs the safe activity and below which it performs the dangerous activity. The value of the threshold is determined by the environmental conditions, implying that animals should have variable 'set points'. Selection pressure to prevent energy stores exceeding the optimal level is usually weak, suggesting that immediate rewards might easily overcome the controls against becoming overweight. The risk of starvation can have a strong influence on the strategy even when starvation is extremely uncommon, so the incidence of mortality during famine in human history may be unimportant for explanations for obesity. If there is an extra risk of switching between activities, the animal should have two distinct thresholds: one to initiate weight gain and one to initiate weight loss. Contrary to the dual intervention point model, these thresholds will be inter-dependent, such that altering the predation risk alters the location of both thresholds; a result that undermines the evolutionary basis of the drifty genes hypothesis. Our work implies that understanding the causes of obesity can benefit from a better understanding of how evolution shapes the mechanisms that control body weight.

Original languageEnglish
Article number20152443
Number of pages9
JournalProceedings of the Royal Society B: Biological Sciences
Issue number1822
Early online date6 Jan 2016
Publication statusPublished - 13 Jan 2016


  • obesity
  • thrifty genotype
  • thrifty phenotype
  • intake regulation
  • energy balance


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