July 11, 2012 -- Losing excess weight by eating a low-fat diet filled with vegetables, fruits, and whole grains appears to help reduce or eliminate menopausal symptoms, according to new research.
"Women who lost weight on a low-fat diet reduced hot flashes and night sweats," says researcher Bette J. Caan, DrPH, senior research scientist at the Kaiser Permanente Northern California Division of Research.
Even some women who followed the diet and didn't lose weight reported fewer menopausal symptoms, Caan tells WebMD, although she says that could be a chance finding.
"The biggest reduction in symptoms was in women who lost weight and were on the diet," she says.
The study is published in the journal Menopause.
Weight Loss & Hot Flash Relief
About 80% of women report hot flashes and night sweats as they progress through menopause, according to Caan. Up to half of them have moderate or severe symptoms. The others have mild symptoms.
The flashes and sweats are thought to result from dilation of the blood vessels close to the skin.
In other research, experts have found that women with a larger body size, including either a higher body mass index (BMI) or a higher percent of body fat, have more frequent or more severe menopausal symptoms.
For the new study, Caan and her team evaluated women who had taken part in the Women's Health Initiative Dietary Modification Trial. That study included nearly 49,000 women, with 40% following a low-fat diet and the others serving as a comparison group.
In all, Caan and her team focused on more than 17,000 women who had participated in the trial. At the start of the study, they were ages 50 to 79. None were on hormone therapy.
Those in the low-fat-diet group ate just 20% of their calories from fat, had five servings of fruits and vegetables, and had six servings of whole grains daily.
All the women reported on their menopausal symptoms, including how often they occurred and how severe they were.
The researchers classified the symptoms as:
- Mild, not affecting usual activities
- Moderate, affecting usual activities somewhat
- Severe, affecting activities so that they could not be done
Low-Fat Diet, Hot Flash Relief Findings
In all, 26% of the women had hot flashes at the beginning of the study, with most reporting mild ones. Twenty-seven percent had night sweats, most of them mild.
After a year, those who followed a low-fat diet were three times more likely to lose weight -- defined as 5 pounds or more -- than those who did not lose weight.
The comparison group was more than two times as likely to gain weight as those following the low-fat diet.
Those who followed the low-fat diet were more likely to be rid of their menopausal symptoms after a year, Caan found.
If they had moderate or severe symptoms and lost 22 pounds or more, they were likely to eliminate their symptoms, she says. If they had mild symptoms and lost 10 or more pounds, they could also eliminate their symptoms, Caan says.
Then came a surprise finding. Women on the low-fat diet who actually gained more than 10 pounds also reported fewer symptoms.
"These findings suggest that weight loss and healthy dietary change could each help to reduce or eliminate [menopausal symptoms]," she says.
Weight Loss & Hot Flash Relief: Why
Caan suspects fat loss itself helps the bothersome symptoms decline. "Fat provides insulation," she says. "You lose it, and you don't need to dissipate as much heat. A hot flash is a way to dissipate heat."
She can't explain for sure why the women on the low-fat diet who didn't lose weight also reported a reduction in symptoms. Other research has found that a higher fiber intake was helpful in reducing hot flashes, Caan says. So the high fiber from the fruits and vegetables and whole grains might have helped.
"It could also be placebo effect," she says. "Women who get a lot of attention [from the study] may be feeling better. They may feel empowered."
Even so, Caan says, the focus should be on the finding that losing weight on a low-fat diet reduced the hot flash risk.
"The biggest reduction in symptoms was in women who lost weight and were on the diet," Caan tells WebMD.
Weight Loss & Hot Flash Relief: Perspective
The new study takes what is known about weight and hot flashes, expands our knowledge, and explains the link better, says Jill Rabin, MD, chief of ambulatory care, obstetrics and gynecology, and head of urogynecology at Long Island Jewish Medical Center. She reviewed the findings.
Doctors have long suspected that women who are overweight or obese tend to have more hot flashes during menopause than those who are leaner, she tells WebMD. "It may be because of the estrogen that is stored in the fat tissues," she says.
The new findings suggest that ''the fat cell itself may be functioning in a way we didn't realize to regulate temperature and produce substances that alter perception of body temperature," she says.
The women on the low-fat diet who didn't lose weight but had fewer hot flashes may have reduced their body fat, Rabin says.
The women in the low-fat diet group also received information about how to overcome obstacles to behavioral change and control cravings, says Alison Huang, MD, assistant professor of medicine at the University of California, San Francisco. She also reviewed the findings.
"These [mental] and behavioral aspects of the program may have made it easier for women to cope with their symptoms or changed their subjective perceptions of their symptoms, so that they no longer perceived their symptoms as being so severe or disruptive," she tells WebMD.
Until more research is in, Rabin says one take-home message is clear from the new research. "Not only will weight loss cut your risk of [heart disease and stroke] and lengthen your life, it may make you feel more comfortable as you go through the menopausal transition and beyond," she says.