We all know — or at least have been repeatedly told — that to lose weight you need to eat less and exercise more. But while the combination of cutting calories and working out will almost certainly make you slimmer, new research shows that there could be an unexpected and alarming side-effect.

A study in the Journal of Bone and Mineral Research this month reported how the combination of dieting and exercise can have a dramatic impact on the health of the skeleton, making bones weaker and raising the risk of osteoporosis, the bone-thinning condition that affects half of all women and one in five men over 50, and is responsible for 300,000 fractures a year in the UK.

Maya Styner, associate professor of medicine