The ecology and evolution of fatness: Evidence from birds and people


Daniel Nettle

Newcastle University
Central European University


In human public health, fatness is seen as a negative outcome and possibly pathological. By contrast, evolutionary ecologists see adipose tissue as an adaptation, and fat storage as a fitness-enhancing strategy under some conditions. We will argue that increased fatness is a plastic adaptation to potential energetic shortfall. This hypothesis is supported by data from experiments on captive European starlings (Sturnus vulgaris) exposed to intermittent food access. A common assumption has been that animals increase fat storage by increasing food consumption. We show that this is not necessarily the case: starlings can gain fat even whilst reducing energy intake. They do this by turning off other functions, such as self-maintenance and repair. Thus, they reduce their risk of starvation, but at the cost of other components of fitness. I will also present data from humans on the phenomenon of 'food insecurity' (intermittent access to food). This also increases fatness, at least amongst women, and also appears to do so without increasing energy intake. I conclude that our knowledge of the evolutionary ecology of animal fatness also helps us understand public health issues in humans.