Menopause and Midlife Weight Gain

Hormonal changes linked to appetite increase

Nov. 12, 2003 (NEW ORLEANS) -- It's well documented that as women go through menopause they tend to gain unwanted pounds but is there a link? The question remains controversial, but a new study offers compelling evidence that the hormonal changes associated with menopause may play a direct role in midlife weight gain.

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Researchers from the Oregon National Primate Research Center report that monkeys who had their ovaries removed, resulting in a more rapid drop in female hormone levels as oppose to the gradual drops changes seen during the menopausal transition, had an almost immediate and dramatic increase in appetite that led to weight gain.

"This has been well documented in studies in smaller animals, but this is the first study to show that it is true in primates," researcher Judy L. Cameron, PhD, tells WebMD. "Studies in humans have been confounded by the fact that eating and exercise habits often change around the time of menopause."

It is clear that as we age there are age-related changes that slow our metabolisms. This, along with a decrease in physical activity can cause weight gain during menopause.

"We know that most women change from pear shaped to apple shaped as they age," says North American Menopause Society spokeswoman Pam Boggs. The 'pear' shape to 'apple' shape refers to a change in the distribution of where we carry our weigh -- whether it's predominately in the hips or around the belly. "But the evidence does not suggest that menopause on its own is associated with weight gain," she notes.

The study reported by Cameron, graduate student Elinor Sullivan, and colleagues included 47 adult female monkeys, 19 of whom have had their ovaries surgically removed. The surgery resulted in a drop in estrogen and progesterone levels, allowing the researchers to try to mimic the hormonal effects of menopause in these animals.

Within four weeks of having their ovaries removed, the monkeys had a 67% increase in food intake and a 5% increase in weight. The surgically altered monkeys also had higher levels of the hormone leptin than the monkeys who still had their ovaries. Leptin is produced by fat cells, and increases in body fat means more leptin is produced. This hormone has been shown to play a role in food intake and metabolism but how it does this remains largely unknown.

Researchers reported results at the annual meeting of the Society for Neuroscience in New Orleans. Findings from the same group of monkeys also show evidence against the popular belief that nighttime eating is associated with weight gain. The researchers found that monkeys who ingested most of their calories at night were no more likely to gain weight than those who ate more during the day.

Cameron says the idea that eating at night leads to packing on the pounds is an "urban myth" she has seen in countless fitness and women's magazines.

"This does not appear to be based on solid science, but it is a very popular notion," she says.

Menopause expert Nanette Santoro, MD, says studying primates instead of people allowed the researchers to better control conditions that could influence weight gain. The main disadvantage is that it is not clear if young monkeys with surgically removed ovaries are an appropriate model for human menopause. Santoro directs the division of reproductive endocrinology at New York's Albert Einstein College of Medicine, Montefiore Medical Center.

"There are all kinds of hormonal changes happening in women at the time of menopause that may also have something to do with weight changes," she says. "Insulin resistance changes with age, for example, but in this experimental model the only variable was estrogen."

The researchers are now studying the same group of monkeys to determine whether giving hormone replacement therapy lowers appetite. Studies assessing the impact of menopausal hormone therapy on weight among menopausal women have been mixed, with some showing a protective benefit for hormone therapy and others showing none.

No matter what the studies show, menopausal hormone therapy expert Barbara Sherwin, PhD, says it is clear that taking hormones will not allow middle-aged women to eat like they could in their 20s.

"The only way to maintain weight as we grow older is to eat less and exercise more," she tells WebMD. "If you eat the same number of calories at 55 that you ate at 25 you are guaranteed to gain weight because your body is not burning calories in the same way."

Reviewed by Brunilda Nazario, MD.

SOURCES: Society of Neuroscience meeting, New Orleans, Nov. 8-12, 2003. Judy L. Cameron, PhD, senior scientist, Oregon National Primate Center, Oregon Health and Science University, Portland. Barbara Sherwin, PhD, professor, psychology and obstetrics and gynecology, McGill University, Montreal. Pam Boggs, spokeswoman, North American Menopause Society. Nanette Santoro, MD, professor; director, division of reproductive endocrinology, Albert Einstein College of Medicine, Montefiore Medical Center, New York City.

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