We can debate obesity until the cows come home but consider this: Nobody has ever gotten healthier by trying to gain 100 lbs. A whole lot of people have gotten healthier by trying to lose 100 lbs.
Sure I could name several people who are thin but live with chronic illness.
My SIL probably weighs 125 lbs, but she's been a type 2 diabetic for about 10 years and is now facing insulin resistence requiring insulin injections. My brother might weigh 140(and he's 6'2"

) but he's drinking himself into oblivion. But for every thin person I can name i bet I can think of 5 heavy people who are strugging with chronic illnesses and their excess weight is not making things better.
Off my soapbox too. Gonna go get some broccoli.