A group of Canadian researchers kept tabs on more than 6,000 middle-aged, obese individuals, and compared their heart disease risk factors to a normal-weight group.

After 14 years, more than a third of the obese study participants showed no increased risk for heart disease—no elevated blood pressure, no hypertension, nothing. In fact, their risk for heart disease was 20 percent lower than the trimmer group, the study found.

On the other hand, the rest of the obese study participants were at roughly double the risk for heart disease than their slimmer counterparts.

The reason: The obese people with healthy hearts ate the recommended amount of fruits and vegetables, and were more physically fit, the study says. They also avoided the type of “yo-yo dieting” that leads to huge weight swings: the healthy group of obese men and women reported less total lifetime weight loss and less frequent dieting than those obese individuals with risk factors for heart disease, the study explains.

What’s wrong with yo-yo dieting? Frequent weight changes lead to fluctuations in your blood pressure, heart rate, blood glucose and lipid levels, and other factors that put pressure on your body’s cardiovascular system, according to a research review published in the International Journal of Obesity.

The obese group with healthy hearts also reported higher average weights at age 21, which indicates those who are naturally bigger—and didn’t start packing on the pounds late in life due to poor diet choices or lack of exercise—may not have reason to fear their fat, the study says.

“This study shows us you cannot use body weight alone to judge health,” explains Jennifer Kuk, Ph.D., a York University professor and one of the study’s co-authors. Kuk says excess weight is still an indicator of poor health for some. But proper diet and exercise are more important factors when assessing heart disease risk.

And take note, skinny people: A recent study shows that even if you’re slim on the outside, you may have stockpiles of internal fat that could lead to heart disease or organ failure.

To keep your heart healthy, regardless of your weight, make sure to eat plenty of fruits and vegetables, the study explains. And aim for at least 15 minutes of exercise every day. A new study from Taiwanese researchers found that 15 minutes of daily physical activity reduces your risk of death by 14 percent and tacks on 3 years to your life.