SEATTLE -- Shedding pounds with diet alone reduces muscle mass but does not increase disability for postmenopausal women, researchers found.
SEATTLE, May 7 -- Shedding pounds with diet alone reduces muscle mass but does not increase disability for postmenopausal women, researchers said here.
Even when women regained the weight with slightly less muscle than before, there was no trend toward decrease in strength heralding disability.
So reported Jamehl L. Demons, M.D., and Mary F. Lyles, M.D., both of Wake Forest in Winston-Salem, N.C., and colleagues, in two analyses of a small but rigorously conducted study.
Although weight loss through diet and exercise together was already known to preserve physical function, unintentional weight loss in older adults often leads to frailty and disability.
So to see what effect caloric restriction alone would have, the researchers analyzed one arm of the larger Diet, Exercise and Metabolism in Older Women (DEMO) study.
Postmenopausal women randomized to the diet-only arm received meals and snacks prepared by the "metabolic kitchen" at Wake Forest tailored to maintain a daily 400-calorie deficit for five months.
The diet was similar to the now-discarded American Heart Association Step I diet, Dr. Demons said. Half the calories were from carbohydrates, 30% were from fat, and 20% were from protein.
The women exercised less than twice a week. Physical activity was monitored with pedometer-style activity monitors and periodic activity logs to ensure exact calorie intake and expenditure balance.
All participants had abdominal obesity, defined by a waist circumference greater than 88 cm, and were overweight or obese (body mass index of 25 to 40 kg/m2).
Dr. Demons and colleagues evaluated short-term outcomes for 23 of these women (ages 50 to 70).
On average, the women lost a clinically significant 11.6 kg (25.6 lbs), which was 12.7% of their total body weight. Of the weight lost, 35.6% was in lean mass (4.1 kg).
Their physical function performance measures at five months compared with baseline were:
Overall, Dr. Demons and colleagues concluded that no functional decline would be expected.
"That was actually a surprising finding because we did know that they lost muscle size," Dr. Demons said.
After the five-month diet, the women returned to preparing their own food without contact with the researchers.
At six and 12 months, Dr. Lyles and colleagues examined 41 women in the DEMO study to see how the body reallocated weight regained, which has rarely been investigated in other diet studies.
Body composition was measured by dual energy x-ray absorptiometry.
They found a large variability in the amount of weight regained, but on average 78% of the lost weight was regained.
Among the findings, Dr. Lyles and colleagues reported:
Some of the weight regain may have been due to "natural progression," Dr. Lyles noted.
Also, the findings cannot be generalized to premenopausal women, she said.
"At menopause, that's when body composition begins to change," she said, with fat predominantly deposited in the abdomen.
Because abdominal fat has been most strongly associated with adverse outcomes in other studies, healthy lifestyle changes become increasingly important at that point.
"We think those changes that happen at middle life predict disability in late life better than the changes that happen in late life," Dr. Lyles said.
Therefore, the findings should be reassuring for overweight or obese women who feel they cannot exercise and for physicians who fear disability from muscle loss, Dr. Demons said.
"In this situation, losing weight by caloric restriction alone did not decrease any of their physical function," she said. "So I think caloric restriction alone is effective."
The prospect of regaining some of the excess weight should not discourage overweight and obese women from making healthy lifestyle changes, the researchers said.
"At both six months and 12 months in spite of weight regain, women had improvement in the traditional cardiovascular risk factors," Dr. Lyles said.
"It's still worth it to lose the weight even knowing that maybe three-quarters of the women will regain some of that weight," she added. "Health-wise they are still better off."
There is some evidence that higher protein intake after a calorie-restricted diet may help preserve lean mass loss, Dr. Lyles said.
The researchers said they learned other practical tips during the study to help women successfully lose weight with calorie restriction.
"One of the hardest things [patients] said was waking up in the middle of the night with hunger pains and a grumbling stomach," Dr. Lyles said. But, the women said that if they waited, the pain went away and then after a night or two the urge for a midnight snack disappeared, she added.
The study is ongoing with additional women -- who have flooded the waiting list on word-of-mouth referrals by prior participants -- Dr. Lyles said.