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 Weight loss efforts among obese adults are linked to an increased
risk of thinning, brittle bones that are prone to fractures, the
study team writes in the Journal of Bone and Mineral Research. While
exercise can strengthen bones and reduce the risk of falls and
fractures, doctors don't yet know the optimal workout routine for
obese people who are dieting.
For the current study, researchers randomly assigned 141 obese
adults to one of four groups: dieters who did only aerobic exercise,
dieters who only did resistance exercise, dieters who did both types
of exercise, or a control group that didn't exercise or diet.
Dieters met with dieticians and did supervised workouts over 26
weeks, while the control group attended some education sessions on
healthy eating.
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.
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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.
One limitation of the study is that researchers only followed people
for about six months, too brief a time to determine whether one type
of exercise might be better than another for fall or fracture
prevention, the authors note.
"Based on this study, one would conclude that (for) an older adult
who is obese and trying to lose weight, the combination of aerobic
and resistance exercise will help the most to maintain their bone
mineral density and their general physical fitness," said Dr.
Cynthia Brown of the Integrative Center for Aging Research at the
University of Alabama at Birmingham.
"Older adults who are able should do muscle-strengthening exercises
(resistance exercise) at least twice a week," Dr. Brown, who wasn't
involved in the study, said by email. "It is recommended that older
adults with multiple chronic conditions make sure they understand
how these conditions affect their ability to exercise and all older
adults should be as physically active as their abilities and
conditions allow."
SOURCE: https://bit.ly/2PHYv9L Journal of Bone Mineral Research,
online December 4, 2019.
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