Fasting and other mild stresses with hormetic effects in Drosophila melanogaster can additively increase resistance to cold.

Mild stresses can have various positive effects in animal models and human beings. Previous studies have shown that fasting, i.e. a short starvation period with water ad lib, increases resistance to a severe cold stress in flies (percentage of survivors 3 days after being kept at 0 °C). Only a few studies have combined two mild stresses with hormetic effects in an attempt to obtain additive effects. Fasting was combined in the same flies with either a hypergravity, cold or heat stress and resistance to cold was observed. When each mild stress had positive effects on this trait (fasting, cold, and hypergravity in males only), their combination had additive effects. However, when one of the mild stresses had no positive effect or even a negative effect (heat), combining it with fasting did not increase the positive effect of fasting or even decreased it.