Vigorous exercise is well known to be the best way to burn off excess calories, but its benefits may go deeper, changing how fat is stored in the first place, Swedish scientists have found.
Six months of regular exercise, such as cycling or aerobics, changed the action of genes involved in laying down fat and the development of obesity.
It also reduced the activity of genes involved in storing sugar from the blood in fat cells. The researchers hope their findings can help in developing drugs to treat obese patients.
Scientists asked 31 slightly overweight but otherwise healthy men to undergo three hours of exercise a week for six months.
None had engaged in regular physical activity before the study, and they were asked to attend one hour a week of spinning classes, on an exercise bike, and two hours of aerobics.
Many failed to attend all the classes and they managed an average of 1.8 hours of exercise a week, but the researchers still found changes to the action of their DNA. Although genes are inherited from a person's parents and do not change through a lifetime, only certain genes are active in any particular cell.
They are turned on or off by a process known as epigenetic imprinting, or methylation. The researchers found that exercise switched on or off more than 7,000 genes. They compared samples of fatty tissue from the volunteers before and after the exercise regime.
Dr Charlotte Ling, a diabetes expert at Lund University in Sweden, said: "Our study shows the positive effects of exercise, because the epigenetic pattern of genes that affect fat storage in the body changes." In further tests, they also found that methylation of two key genes reduced the amount of free fatty acids.
Excessive levels of free fatty acids in the blood are associated with type 2 diabetes and the findings may help to explain why exercise can reduce the risk of the disease in patients.
The researchers hope drugs can be developed to target the same genes. The study is published in the journal 'PLOS Genetics'. (© Daily Telegraph, London)