Obesity and the limits of BMI

Obesity is a chronic disease in which the body ends up storing more fat than it should. Energy that comes in and doesn't get used can be put away as fat, a bit like a pantry that keeps filling up with food that never made it to the table. In adults it's estimated with body mass index, a number that comes from combining weight and height; it's worth knowing what that is and what it isn't, because it doesn't measure fat, it infers it from the outside, indirectly.

Obesity doesn't come in through a single door either. Biological factors, behavior, the environment a person lives in, their social situation and medical factors all push at the same time, which is why no single reason explains it. When you look at whole populations rather than one individual, type 2 diabetes, diseases of the heart and blood vessels, and other chronic diseases show up more often among people living with obesity.