Exercise changes the way fat is stored We show a general global increase in adipose tissue DNA methylation in response to 6 months exercise. The scientists, whose study is published in the journal PLOS Genetics, asked 31 slightly overweight but otherwise healthy men to undergo three hours of exercise a week for six months. None of the men had enganged in regular physical activity before the study, and they were sked to attend one hour spinning classes and two hours of aerobics each week. However, many of the men failed to attend all classes and they managed an average of 1.8 hours a week, yet the researchers still found changes in the levels of epigenetic imprinting. The researchers took tissue samples from the body fat of the volunteers before and after the exercise regime and compared the level of epigenetic imprinting on both. After analysing 480,000 sites in each persons DNA, they found 17,975 locations were altered on 7,663 genes. The human genome contains around 20,000 genes. The scientists claim the findings show the complex interaction between genes on diseases like obesity. Scientists believe this extra layer of information that attaches itself to DNA helps to explain how our environment can interact with our genes. Our genes themselves are determined by those we inherit from our parents and do not change through our lives. "The absolute changes in DNA methylation observed in response to the exercise intervention are modest," said Dr Ling. But the large number of affected sites may in combination potentially contribute to a physiological response. In a further set of tests they also looked at how certain genes could affect the storage of fat and showed that methylation of two key genes reduced the amount of free fatty acids. Excessive levels of free fatty acids in the blood are known to be associated with type 2 diabetes and may help to explain why exercise can reduce the risk of the disease in patients. The researchers hope that by targetting genes that are affected by exercise it may produce new targets for drugs in the treatment of obese patients. Tina Rönn, another of the researchers on the study, said: "This suggests that altered DNA methylation as a result of physical activity could be one of the mechanisms of how these genes affect the risk of disease. We now have a map of the DNA methylome in fat.