Being fat is a risk factor and a complicating for an alarming number of considering ailments. There's a reason why fat people get hammered at the doctors office about losing weight.
HOWEVER, the obesity epidemic in the US and other Western countries is a result of a fucked-up food system and an urban planning system that encourages a sedentary lifestyle. Like, individuals can choose to be less fat on their own, yes, but we're not going to make progress on this issue as a society unless we agree to change the fundamentals causing the problem.