Dieting Without Exercise Harms Bone Health

plate with a measuring tape wrapped around it

Men and women who lose weight through caloric restriction, without exercise,
also lose bone at the hip and spine, increasing their risk for the bone-thinning
disease osteoporosis and fractures, a study shows. Adding regular exercise to a
calorie-restricted diet helps shield the bones from the harmful effects of

“Exercise protects
against bone loss during voluntary weight loss,” Dr. Dennis T. Villareal, who
led the study, told Reuters Health. “Therefore, it would be important to combine
calorie restriction and exercise to derive the benefits of weight loss and
preserve bone.”

Villareal, from
Washington University School of Medicine in St. Louis, and colleagues studied
the effects of weight loss on bone loss in 30 women and 18 men whose average age
was 57 years. The study subjects were overweight but not obese.

For one year, 19
subjects stuck to a calorie-restricted diet; 19 ate their usual number of
calories but engaged in regular exercise; and 10 in a comparison “control” group
received healthy lifestyle tips only. All but two participants completed the
yearlong study.

At the end of the 12
months, the dieters lost an average of 18.1 pounds, while the exercisers lost
14.8 pounds and those in the control group had no significant change in their

As reported in the
Archives of Internal Medicine, the dieters lost an average of 2.2 percent of
bone density in the lower spine and at the hip. In contrast, there were no
significant changes in bone mineral density in the exercise group or healthy
lifestyle groups.

The action of
muscles pulling on bones during exercise is thought to produce “healthy” strain
on the skeleton that stimulates the production of new bone, the investigators
note. The current study supports this line of thought.

“It’s important that
calorie restriction not be seen as a bad thing,” Villareal said, “because it
offers enormous benefits with respect to reducing disease risk and is effective
for weight loss. Also, there is a real possibility that calorie restriction
provides anti-aging benefits that cannot be achieved through exercise

However, to maintain healthy bones, “exercise should be an important
component of a weight loss program to offset adverse effects of calorie
restriction on bone,” the team concludes.