Discussion: I'm overweight. The GP told me that lean people are healthier. I'm not convinced he's right?

Let's get some order in what your doctor probably tried to explain. The conclusion is that it is difficult to draw unequivocal conclusions regarding most populations!

Healthy people usually maintain the optimal weight for their body structure. (They are not necessarily thin) Obese people are often unhealthy as being overweight due to an unhealthy lifestyle and poor nutrition. Medium overweight regarding their age (who are a large part of the population), are not necessarily healthy but are also not necessarily sicker than others. Thin people are also not necessarily healthier than overweight people. Good health is a dynamic result of nutrition, lifestyle, environment, and genetics.