Weight-bearing exercise does not prevent increased bone turnover during weight loss, according to a new study.

Bones are remodelled – breaking down old bone and forming new bone – during weight loss at an accelerated rate. As a result, bone density is reduced, causing increased fragility.

According to the Department of Nutrition and Exercise Physiology at the University of Missouri’s College of Human Environmental Sciences, weight-bearing exercise such as fast walking or jogging, did not prevent the increased bone turnover.

However, Pam Hinton, associate professor in the department, said: “Accelerated bone turnover is not favourable, but the potential negative consequences of increased bone turnover do not outweigh the numerous other health benefits of weight loss.

“Adequate intake of calcium and vitamin D may minimise the reduction in bone density during weight loss.”

The researchers examined the bone turnover markers in the blood of overweight, premenopausal women. These bone markers, which are released by the bone cells that are involved in bone breakdown and formation, are used as indirect indicators of bone remodelling.

After six weeks, women who lost 5 per cent of their body weight by calorie-restriction or participating weight-bearing exercise experienced an increase in bone turnover markers, as did those who lost weight by calorie-restriction only or by participating in non-weight-bearing exercise.

“These findings should not affect the prescription of aerobic exercise during weight loss,” said Hinton. “The rationale for recommending aerobic exercise during weight reduction is to increase energy expenditure and maintain lean body mass.”