One reason that BMI is a poor gauge of obesity and overall health is that defects some people’s ability to store fat can lead to conditions such as diabetes, non-alcoholic fatty liver disease, and heart disease, even in people who are thin.

That’s the upshot of new research that is attempting to understand why some thin individuals still suffer from conditions primarily linked to obesity, while some overweight individuals are largely healthy, The New York Times reports.

The key may have little to do with body fat content itself, but rather with each person’s ability to store it. With that understanding, scientists are now working on drug treatments to protect people from excess fat and spare them from dire medical conditions.

One in three Americans and one in four adults worldwide have at least three conditions associated with obesity such as diabetes, high cholesterol, and high blood pressure — a combination that doubles their risk of heart attacks and strokes.