The evolution of body fatness: trading off disease and predation risk

John R. Speakman
  • Journal of Experimental Biology, March 2018, The Company of Biologists
  • DOI: 10.1242/jeb.167254

Why do animals store fat and what regulates the level of fat they store

What is it about?

Body fat serves to store energy. The level at which individuals are presumed to regulate their stores of fat has been suggested to be dominated by two contrasting forces. First, the risk of a catastrophic failure of food supply pushes the level of stored fat upwards. However, storing fat makes individuals more vulnerable to the risks of predation. So the regulated level of fatness is regarded as the outcome of this trade-off. In this paper i suggest that it is more likely that the factor forcing up fatness levels is the risk of contracting disease. That is when animals contract disease they experience suppression of the drive to eat presumably to minimise the risk they will fall prey to predators in their debilitated state and must rely instead on stored fat. Using a mathematical model I show that these contrasting forces will more likely lead to a system for fat regulation that has dual intervention points rather than a single set point.

Why is it important?

understanding the evolutionary background of fat storage is important for understanding why we have a modern obesity epidemic.


Professor John Speakman

For a long time I have felt that the idea that we store fat to survive periods of catastrophic failure in food supply is flawed. Yet we clearly store fat for some reason. This paper is my attempt to provide such an alternative reason.

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The following have contributed to this page: Professor John Speakman