Although everyone can benefit from exercise, the mechanistic links between physical fitness and overall health are not fully understood, nor are the reasons why the same exercise can have different effects in different people. Now a study published in Nature Metabolism led by investigators at Beth Israel Deaconess Medical Center (BIDMC) provides insights related to these unanswered questions. The results could be helpful for determining the specific types of exercise most likely to benefit a particular individual and for identifying new therapeutic targets for diseases related to metabolism.