WEDNESDAY, June 15 (HealthDay News) -- Severely obese patients who suffer from migraines may see them fade or become less frequent after having weight-reducing gastric bypass surgery, University of Iowa researchers say.

In the three years following surgery, 70 percent of the patients reported being migraine-free and more than 18 percent saw their migraines reduced from five to two a month, the researchers found.

"The association between migraine and obesity is controversial," said lead researcher Dr. Isaac Samuel, director of the University of Iowa Obesity Surgery Program. "Some people say the risk for migraine is higher in obese people; others say the symptoms are worse," he said.

There could be a number of reasons why migraine is relieved by gastric bypass surgery, including hormonal changes that occur after the procedure or certain proteins produced by fat cells, Samuel said.

"Severely obese patients with migraine should be encouraged to have gastric bypass if they want relief of the symptoms," Samuel said. "In addition, people who are obese, but not severely obese, should be encouraged to lose weight if they have migraine."

The findings of the study were due to be presented Wednesday at the 28th Annual Meeting of the American Society for Metabolic & Bariatric Surgery in Orlando, Fla. Since the study is small and it has not appeared in a peer-reviewed journal, its findings should be considered preliminary.

Like all other operations, bariatric surgery carries some medical risks, including. serious infections, internal bleeding, blood clots, and death, according to the American Society for Metabolic & Bariatric Surgery (ASMBA). The organization reports that the overall risk of serious complications is about 4 percent and the risk of dying is one in 1,000.

Weight-loss surgery is also expensive, costing from $17,000 to $35,000 or more, depending on the type of procedure performed.

For the study, Samuel's team reviewed the medical records of 702 patients who underwent gastric bypass surgery between March 2000 and September 2009. In addition to being obese, the patients also suffered from migraines. Of these patients, 81 were selected for the current study.

The researchers found that gastric bypass surgery improved or completely alleviated migraines in most patients. The most pronounced effect was among those patients whose headaches started after they became obese, the researchers note.

Of those who had their first migraine before becoming obese, 46 percent became migraine-free and 29 percent experienced some improvement, Samuel's group says.

These findings were independent of problems associated with migraine such as depression, anxiety or sleep apnea, the researchers added.

Other causes of headache in obese people include pseudotumor cerebri, or idiopathic intracranial hypertension, which is an increase in pressure around the brain that can feel like a migraine and may be caused by obesity. This type of headache also responds well to gastric bypass surgery, the researchers noted.

Commenting on the study, Dr. Elizabeth Loder, chief of the Division of Headache and Pain at Brigham and Women's Hospital in Boston said that "this is an interesting observation but the data seem quite preliminary."

In the absence of a control group, it is not possible to say whether the surgery and ensuing weight loss really "caused" the improvement in migraine, she said.

"Migraine is a condition that naturally waxes and wanes," Loder said. "Some of the improvement might simply reflect this variable disease activity. It is also the case that people who undergo surgery of any kind often report temporary improvement in headaches," she said.

Without a similar group of patients who did not undergo surgery, it is not possible to distinguish among these possibilities, Loder explained.

"In addition, it is unclear what is meant by complete, partial and no resolution, Loder said. "It would be very, very unusual for any treatment to cause complete resolution of migraine," she said.

Another expert, Dr. Richard B. Lipton, vice chairman of neurology, and director of the Montefiore Headache Center at the Albert Einstein College of Medicine in New York City, felt that the findings underscored the need for further research.

"These data are compatible with the epidemiologic studies showing that obesity is a risk factor for migraine progression," he said. "In addition, there is another published observational study showing that migraine improves after bariatric surgery in proportion to the extent of weight loss. Randomized trials are badly needed."

More information

For more information on diabetes, visit the U.S. National Library of Medicine.