Prehistoric humans often had to cope with food shortage. Agriculture brought food security and a longer life. But food abundance comes with a cost: research shows that being overweight can make us age faster and increase the risk of diseases such as cancer. The reason may be that a set of core genes control our metabolism, cellular maintenance and, perhaps, the ticking of our biological clock: understanding how our food intake can act on these genes is a key goal for public health. But, because of the diversity of their food habits, humans are challenging to study. Here, I will focus on an exotic but well-known model of human fasting: the King penguin. These birds can go for weeks without eating, and can switch between obesity and underweight several times a year without negative effects: yet in the zoo, they have food in plenty, medical care, and don't exercise much. I hope studying penguins will teach us how the transition to a modern lifestyle can impact health and ageing in humans.

2023

2027