This comment is Dunning-Kruger. Some overweight people are very unhealthy. Some thin people are very unhealthy. Some overweight people have genetics that prefer to store fat subcutaneously where its not very harmful. Some thin people have genetics which preferentially store fat in and around organs or muscles which is incredibly damaging, leads to chronic inflammation and eventually T2D and atherosclerosis, among others. Lets just say you can't judge a book by its cover and biology is complex. Unless you know a person, keep your mouth shut and your mind open!
There are sedentary thin people who live on doritos and active heavy people who eat salads. There are ALL KINDS!
Over 3 gigabases is a lot of room for genetic diversity, don't you think?