Runners burn more calories – even at rest

• 26 October 2008
• NewScientist.com news service

THE benefits of exercise don't stop when the running shoes come off. A new peek inside the muscles of resting athletes shows that they burn fuel even when their bodies don't need the energy.

Endurance sports such as long-distance running are known to increase the number of mitochondria, the tiny engines inside cells that convert sugars and fats into ATP molecules, the cell's energy carriers. This boosts the capacity of muscles to consume oxygen and work at higher power during exercise.

Now Douglas Befroy and his colleagues at Yale University say that the

mitochondria in the muscles of men who run at least 4 hours a week consume 54 per cent more fuel at rest than those of men who don't run

(Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0808889105). Yet the amount of ATP produced by the two sets of men was the same, indicating that when at rest the extra fuel was being "wasted", and turned into heat.

Because mitochondrial fuel-burning helps to clear out the cellular fats thought to contribute to insulin resistance, this finding suggests a way that training can help to protect against type 2 diabetes even when exercise is over.

From issue 2679 of New Scientist magazine, 26 October 2008, page 15