Researchers know diet can help boost the effects of exercise to prevent muscle loss in old age, but are not sure exactly what works and what doesn't.

Between 30 and 50 percent of muscle mass is often lost after the age of 40, resulting in a reduced ability to carry out everyday tasks; this degenerations is known of as sarcopenia, the University of Southampton reported.

 "Sarcopenia is now recognised as a major clinical problem for older people. Gaining insights into the effects of lifestyle on losses of muscle mass and strength will be essential for the development of future public health strategies to promote better health in later life," said Avan Aihie Sayer, Professor of Geriatric Medicine at the MRC.

A team of researchers looked at combined diet and exercise training trials in men and women over the age of 65 and a number of scientific articles on the subject.

"Poor diets and being physically inactive are common in older age. Understanding the benefits of maintaining sufficient levels of physical activity and diet quality to prevent sarcopenia is therefore a priority," said Sian Robinson, who led the review. "Although some studies have found enhanced effects of exercise training when combined with diet supplementation, our review shows that current evidence is incomplete and inconsistent. Further research to determine the benefits of supplementation and exercise training for older people is therefore needed."

The study was funded by the Medical Research Council and published in a recent edition of the journal Clinical Interventions in Aging.