"It could be that estrogen levels are higher in the fat, but not circulating in the blood," she said. "Its the blood that gets to the brain and to the thermoregulatory centers that govern hot flashes."
A third analysis, published in the journal Fertility and Sterility, examined the influence of alcohol consumption on hot flashes in midlife women.
This study attempted to explain an earlier finding that moderate alcohol consumption (up to three drinks per month) actually reduced the severity of hot flashes by 25 percent. This effect vanished in women who consumed more than three drinks per month.
Because alcohol consumption is known to affect metabolism in some animals, the team thought that light drinking might alter sex steroid hormone levels in midlife women. But their analysis failed to turn up any significant hormonal differences between the alcohol users and the women who never used alcohol.
"We dont know why (moderate alcohol consumption) is reducing the risk of hot flashes, other than it doesnt seem to be doing so by changing hormone levels," Flaws said.
Together, these studies point to some risk factors for hot flashes that women can change and others that cannot be changed, Flaws said.
"Body mass index, alcohol use and smoking are three things that can change," she said. "So probably if women quit smoking, and they lose weight, it will reduce their risk. If they (engage in) light drinking, that might also reduce the risk of hot flashes. And then theres the genetic piece, which we cant change."