Article content continued

People in all three diet groups lost about 9% of their body weight during the study, compared with 1% in the control group.

Bone density measured at the hip decreased less for the people who did resistance exercise alone or in combination with aerobic workouts than it did for others.

“When undergoing weight loss therapy, patients should incorporate as much as possible some resistance exercise to protect against bone loss,” said senior author Dr. Dennis Villareal of Baylor College of Medicine and the Michael E DeBakey VA Medical Center in Houston, Texas.

“Resistance exercise should be at least moderate in intensity,” Dr. Villareal said by email. “We do not know if less-intense exercise would be effective in protecting against bone loss during weight loss.”

Despite the health risks associated with obesity, weight loss programs for older adults can be risky because people can lose muscle mass and bone density as they slim down, the study team notes.

In the study, resistance exercise was associated with a smaller decline in lean muscle mass as well as smaller decreases in bone density than aerobic workouts.

Participants were 70 years old, on average, and all had a BMI of 30 or greater at baseline.

In the exercise groups, participants were given customized diets designed to create a deficit of about 500 to 750 calories a day. They also did supervised one-hour workouts three times a week.

Aerobic exercises included walking on a treadmill, riding a stationary bicycle, and stair climbing. Resistance exercises included upper- and lower- body exercises using weight machines. All of the exercisers also did some activities designed to improve balance and flexibility.