Eating well is certainly essential for healthy survival but if you want to live longer, then all you need to do is reduce your diet rather than skipping off to the gym.
Derek Huffman, from the University of Alabama in Birmingham, found that eating less prolongs life in rodents and said that now he knows one of the key molecules involved.
It's probably down to depressed insulin levels, which regulate blood glucose, he said.
For the study, Huffman kept mice on a variety of diets and exercise regimes.
He found that insulin was lowest in animals eating the least, even if they didn't exercise.
However, Huffman warned that it is still unknown if the effect translates to humans, so keep exercising.
"The benefits of exercise in humans are overwhelming," New Scientist quoted Huffman, as saying.