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.