Women who add more fat to their frames as they approach menopause will have a harder time with hot flashes, a new study in the American Journal of Epidemiology shows.
People used to think that fat helped protect against hot flashes because it contains hormones that can be converted into estrogen, Dr. Rebecca C. Thurston of the University of Pittsburgh School of Medicine and her colleagues note in their report. But recent research has shown that women with higher body mass indexes and more body fat may actually suffer more hot flashes, they add.
"Gains in body fat are common over the course of midlife and the menopausal transition, which is probably no news to anybody," Thurston noted in an interview.
To investigate whether these gains might be related to menopausal symptoms, she and her colleagues followed 1,659 women 47 to 59 years old for four years. Every year, they checked women's hormone levels, percentage of body fat, and frequency of hot flashes and night sweats.
During follow-up, 53 percent of the women showed an increase in body fat — on average, about a half percent. In 24 percent of the women, body fat percentage shrank, while it remained stable for the remaining 23 percent.
The women who gained fat were 1.23 times as likely to report having hot flashes, the researchers found. The relationship remained after they accounted for the women's hormone levels, but was not significant for night sweats. This may be because, Thurston told Reuters Health, it's simply harder to keep track of night sweats, largely because they happen while one is sleeping.
As people age, body fat percentage typically increases, in part due to weight gain, and in part due to loss of muscle mass, Thurston noted. Avoiding such gains by maintaining a healthy diet and being active could help women head off hot flashes as menopause approaches, she added, and can also help prevent heart disease, which is more of a threat to women after menopause.
Researchers believe, she added, that fat might worsen hot flashes because it acts as an insulator and makes it harder for the body to get rid of heat. Hot flashes and night sweats may happen, she explained, because it's tougher for a woman's "internal thermostat" to maintain a steady core body temperature during menopausal hormone shifts.