Frequently gaining and losing weight can increase risk of death by heart attack. Also dangerous: eating a yo-yo.

Losing and regaining those stubborn 10 pounds over and over again could be more dangerous than you think.

Healthy women who yo-yo dieted were 3.5 times more likely to die suddenly from a heart attack than women whose weight remained stable, according to research presented at the American Heart Association’s Scientific Sessions on Tuesday.

These deadly results were seen in women with “normal weight” who fluctuated 10 pounds or more in either direction. Weight cycling in normal-weight women was also associated with a 66% greater risk of dying from coronary heart disease.

Researchers at Brown University’s Memorial Hospital of Rhode Island studied the self-reported weight history from more than 158,000 postmenopausal women ages 50 to 79, which they divided into four categories: stable weight, steady gain, maintained weight loss and weight cycling. They followed up with them after just over 11 years.

Weight cycling had a deadly impact on normal-weight women, who weren’t just more likely to die of heart attack, but they also died fast — within an hour of cardiac arrest.

But overweight and obese women who weight-cycled didn’t see an increased risk in either type of death. There was also no higher mortality among women who put on pounds but didn’t lose them, or among those who lost weight and kept it off.

These findings support previous reports that suggest you might be better off just hanging onto the extra pounds than repeatedly winning and losing the battle of the bulge. Cognitive Neuroscience recently reported that “chronic dieters” are changing the structure of their brains to have less of the white matter associated with the noggin’s communication system and reward center. Yo-yo weight loss can also wreak havoc on muscle mass, hydration and electrolyte balance.

“Weight cycling is an emerging global health concern associated with attempts of weight loss, but there have been inconsistent results about the health hazards for those who experience weight cycling behavior,” said Dr. Somwail Rasla, the study’s lead author.

He suggested to the “Today” show that yo-yo dieting stresses the body as blood pressure and glucose rates keep rising and falling to adjust to weight loss and gain. “We did a trial on a mouse model and found that mice exposed to weight cycling behaviors ended up with damage to their DNA,” he said.

This study was only observational, however, meaning it doesn’t show a true cause-and-effect relationship. And it’s unclear whether the self-reported weights of these women were truthful, or if they had underlying medical conditions that could have caused their heart attacks.

“More research is needed before any recommendations can be made for clinical care regarding the risks of weight cycling, since these results apply only to postmenopausal women and not to younger-aged women or men,” Rasla said.