There are rare circumstances when weight is influenced by a medical condition, but generally it’s people eating too much and not moving enough.
Do you have any idea how many medical conditions keep people from not moving enough (thereby causing people to eat more calories than they need)? It’s NOT rare. Hell, lower back pain is one of the most common reasons people go to the doctor, and guess what’s a lot harder to do when your back is screwed up? Exercise.
I am a bicyclist. I love riding. I ride any chance I get. I also currently have chronic problems in my upper, middle and lower back, including a herniated disc in my low back, and it’s aggravated by bicycling more than anything else. I’ve been seeing doctors for 20 years for my back problems, since I was a teenager. I had back problems when I was a size 2, and I have back problems as a size 12.
People will probably want to respond to my comment by saying that diet is a bigger factor in losing weight than exercise, or that people should adapt and find other ways to be active if they can. What I am saying is that weight, medical conditions, and eating more calories than a person can burn – they’re all connected and it’s a very common problem.