Some studies, though not all, have found a connection between excess pounds and a higher rate of migraine. But they have mainly studied people at one point in time - leaving it unclear whether the pounds or the migraines came first.
In the new study, researchers looked at data from the Women's Health Study, a long-term clinical trial that began following thousands of U.S. women in the mid-1990s.
Overall, women who had migraines at the outset were no more likely than other women to become overweight or obese over the next 13 years. And the average weight gain in both groups was almost identical, at around 10 pounds.
"We do not see convincing data that migraine should be considered a risk factor for the development of obesity," Kurth said.
In theory, migraines could contribute to weight gain indirectly. Frequent or severe headaches could keep a person from regular exercise, for example.
But the new findings, reported in the journal Cephalalgia, do not support that theory.
The results are based on 19,162 female health professionals who were age 45 or older, and normal-weight, when they entered the study. Almost 3,500 reported a history of migraines.
Over the next 13 years, 41 percent of those women became overweight, while about 4 percent became obese. The odds of becoming obese were no greater among women with a history of migraine, and the risk of becoming overweight was only slightly higher - 11 percent.
Severe migraines did not seem to carry a risk of extra pounds, either, Kurth's team found. Women who had migraines weekly to daily were at no greater risk of becoming overweight or obese than those whose migraines came a few times a year.
The study did not look at the question in the other direction: Are overweight or obese women at increased risk of migraines, or more severe ones?
"This is still possible," Kurth said. "In fact, several studies have now shown that obesity is associated with increased migraine frequency."
There is also some evidence tying obesity to an elevated risk of developing migraines in the first place, Kurth said.
But, he added, the prevalence of migraine has remained stable in recent decades, while obesity rates have soared. So it would not seem "reasonable" to assume obesity is causing cases of migraine, Kurth said.
A limit of the study, the researchers say, is that all of the women were at least 45 years old at the start, and still normal-weight at that point. So it's not clear if the findings would be the same for young women.
SOURCE: http://bit.ly/Q7YCsw Cephalalgia, August 8, 2012.