Overweight adults can be healthier than thin adults.

That’s the surprising conclusion from a new study by the University of Michigan. It shows that your weight doesn’t predict the state of your health nearly as well as the size of your…

… oh, we’ll get to that in a minute.

But first, here’s what the researchers concluded about weight and health.

According to the study, approximately 51% of overweight adults in the U.S. have normal cholesterol, triglycerides, blood pressure, and blood sugar readings. Close to 33% of obese adults in the U.S. are healthy, too.

But around 25% of thin adults have unhealthy readings in 2 or more of the same categories — cholesterol, triglycerides, blood pressure, and blood sugar. That’s 16 million thin adults who have the kind of health risks that are usually linked to obesity.

How Can This Be?

To start with, the experts are beginning to rethink how they define “overweight.” Traditionally, they used BMI, or body mass index, a ratio of weight to height that doesn’t take into account whether your body is fat or lean.

Using BMI, many professional athletes would be considered to be overweight.

But no matter what your weight or BMI, heart health risks are more prevalent in smokers, older people, and people who rarely or never exercise.

For obese people between the ages of 50 and 64, only 2 out of 10 are deemed to be healthy. For younger obese adults, the healthy ratio is 5 out of 10.

But the researchers aren’t ready to say that excess weight doesn’t carry health risks. At a minimum, this study reinforces the importance of regular exercise for maintaining good health.

One Result Did Jump Out

And the experts took notice.

Whether you’re overweight or thin, a thick waist is linked to a higher risk of heart disease. That’s because a thick waist can mean that your abdominal organs are surrounded by internal fat deposits.

That increases your risk of high blood pressure, high cholesterol, high triglycerides and high blood sugar.

So now you know — whether you’re overweight or thin — it’s the size of your waist that may matter most to the state of your health.