Previous studies have shown reducing DAF-2 function during development affects only fertility, but in adulthood reducing function affects only lifespan. The researchers concluded that the two effects influenced different parts of the IIS pathway and their affects could be isolated.

Efforts focussed on a key target in the IIS pathway in the fruit fly, dFOXO. Known as a transcription factor, it helps activate and regulate genes.

They found that increasing levels of the transcription factor dFOXO in the fat cells of female fruit flies from the onset of adulthood increased lifespan by between 20 and 50 per cent and reduced fertility by 50 per cent. But no effect was observed in male flies.

The functions of fruit fly fat include many of the metabolic activities of mammalian liver and fat storage. In mice deletion of insulin receptors in white fat cells results in a lean long living adult. Together this suggests that fat tissue is crucial in extending lifespan by altering the IIS pathway, said Dr Giannakou.

Further work needs to be done to determine why there is a different affect in both sexes, added Professor Partridge.

It could be because females are more influenced by food and its consequences. They make things “ eggs, babies, and need a lot of nutrients for this. Males tend to move around a lot - to find females and persuade them to mate, and need less nutrients to make things. But this is just speculation.

The study was funded by the Wellcome Trust and the Biotechnology and Biological Science Research Council.

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