Losing Weight? Don't Also Lose Bone
If you're on a weight-loss diet, do more weight-bearing exercise to counter the potential adverse effects that this might have on your bones. That's a take-home message of a recent study in the Journal of Bone and Mineral Research, which used data from 1,361 people in the Framingham Offspring Cohort, begun in 1971.
Those who lost at least 5 percent of their body weight over the past four to six years or over the long term (40 years) were found to have lower bone density and greater deterioration in bone microarchitecture than those whose weights were stable. This was after age, smoking, physical activity, medical history (including diabetes, cardiovascular disease, cancer, and prior fractures), and other potential confounding factors were controlled for. The association was stronger at weight-bearing parts of the skeleton. Using their results together with other study findings, the researchers estimated that weight loss of 5 percent or more over 40 years may nearly triple the risk of fracture.
The study did not look at the actual incidence of fractures. But weight loss, both intentional and unintentional, has previously been found to be associated with bone loss and fractures in older people, possibly due to decreasing mechanical load on bones as body mass decreases, hormonal changes, or decreased nutrients, such as protein, when fewer calories are consumed. And though the study did not test the effects of weight-bearing exercise, such activities can improve bone density by putting stress on bones, with greater force resulting in greater results. The best exercises include running, jumping rope, stair climbing, and weight lifting, but walking and low-impact aerobics, for example, are also good. (Swimming, cycling, and other nonimpact exercises are least beneficial for bones.)
To protect your bones, be sure also to eat a healthy diet that includes adequate calcium, vitamin D, and other bone-essential nutrients, and take calcium and vitamin D supplements if your diet falls short in these nutrients.