If you’ve always been a normal weight without having to try too hard, you may consider yourself lucky. But the mirror and the scale only tell part of the story: You can look great in a bikini or have a body-mass index (BMI) in the normal range, but if you don’t take care of yourself, you could be just as unhealthy as an obese person.
This phenomena—sometimes known as skinny-fat, or “normal-weight obesity”—may affect up to one-fourth of normal weight people, according to one 2008 study. “They look healthy, but when we check them out they have high levels of body fat and inflammation,” says Ishwarlal Jialal, MD, director of the Laboratory for Atherosclerosis and Metabolic Research at UC Davis Health System. “They’re at high risk for diabetes and cardiovascular problems, but you wouldn’t know it from their appearance.”