Weight Loss May Benefit Bone Density

Contrary to common thought, overweight and obesity do not have a beneficial effect on bone mass, according to research recently published in the Journal of Clinical Endocrinology and Metabolism. Epidemiological studies have suggested that high body weight or body mass index (BMI) is linked to high bone mass, and that reducing weight may cause bone loss.

A study based on a sampling of people in the U.S. and the People's Republic of China suggests that the opposite is true. Researchers contend that previous studies were confounded by bias or flawed reasoning. Calculations involving weight or BMI fail to take the mechanical loading effect of body weight into account, they argue. The important variable, according to the group, is the percentage of body fat.

Investigators took detailed measurements of 1,988 unrelated Chinese participants and 4,489 Caucasians from the American Midwest. The measurements include whole body fat mass, lean mass, percentage body mass, BMI, and bone mass.

When researchers adjusted bone mass results to remove the mechanical loading effects of body weight, they found an inverse relationship between fat mass and bone density. The researchers linked an increasing percentage of fat mass with diminishing bone density. Losing weight is likely to tilt the equation in the other direction, contributing to greater bone density, the researchers conclude.