Should you lift weights while losing weight to keep your bones strong?

When you lose weight, you may also lose bone. And that can spell trouble, especially for older adults, whose bones become more fragile with age.

Solution: “Exercise can minimize weight-loss-induced bone loss,” says Dennis Villareal, a physician at the Michael E. DeBakey Veterans Affairs Medical Center in Houston.

Villareal and his colleagues randomly assigned 107 older adults with obesity to one of four groups:

  • a diet group that cut 500 to 750 calories a day,
  • an exercise group that did balance, flexibility, aerobic, and strength training three times a week,
  • a diet + exercise group that did both, or
  • a control group that didn’t change their diet or exercise. 

After a year, both groups of dieters had lost close to 10 percent of their starting weight. (The exercise-only and control groups didn’t lose any weight.)

Compared to the control group, hip bone density dropped only in the diet group. It increased in those who did exercise alone and decreased less in the diet-plus-exercise group.

Which type of exercise best preserves bone?

In a new study, Villareal randomly assigned 160 older adults with obesity to one of four groups.

The control group made no changes. The other three groups cut 500 to 750 calories a day and did one of the following three times a week for six months:

  • aerobic exercise like treadmill walking, stair climbing, or cycling,
  • strength training using weight-lifting machines, or
  • aerobic + strength training.

“All three of the groups who dieted and exercised lost about 9 percent of their starting weight,” says Villareal.

“But aerobic exercise didn’t prevent weight-loss-induced bone loss, whereas strength training alone or combined with aerobic exercise was equally effective at diminishing bone loss.” Ditto for lessening muscle loss.

The bottom line

“When you diet, do exercise, with an emphasis on strength training,” says Villareal.