Physical exercise has the ability to instantly change DNA molecules within muscles to make them fight fat more effectively, according to a study by Karolinska Institutet (KI) in Stockholm, Sweden.

A study in cell metabolism conducted by the university showed that DNA within skeletal muscle taken from people after a burst of exercise had fewer methyl groups than it did before exercise.

The changes in methyl levels took place in stretches of DNA that serve as landing sites for different kinds of enzymes, called transcription factors, which in turn are involved in 'turning on' genes already known to be important in muscles' adaptation to exercise.

If methyl groups are firmly in place, transcription factor 'keys' are prevented from entering the DNA 'locks' that aid muscle capacity. But when the methyl groups are removed, it allows the keys to turn the locks and boosts the capacity of muscle for work.

The study was lead by Juleen Zierath, professor of clinical integrative physiology at KI. She called the discovery significant as it confirms that exercise helps the body become more healthy within minutes.

She said: "Exercise is already known to induce changes in muscle, including increased metabolism of sugar and fat.

"Our discovery is that the methylation change comes first."

"We often say 'You are what you eat.' Well, muscle adapts to what you do. If you don't use it, you lose it and this is one of the mechanisms that allow that to happen."

To read KI's press release on the findings, click here.