This is a very similar thing as saying people choose to be poor. Do you agree with that?
I have been physically fit my whole life. The comments people make to me in casual conversation might raise your eyebrows. They don't say, "I wish I weren't overweight, and I feel powerless to do anything about my problem." Instead, they say things like, "HAW HAW HAW I don't run unless chased HAW HAW HAW!" They say, "I hate vegetables, I can't stand them. How can you eat steamed brussels sprouts? How do you go without sweets?"
They can't figure me out. They just don't understand how it's possible to work out twice a day, take two 15-minute walks, and restrict my daily calories to 2000. They can't figure out why I don't eat bacon all the time, like they do. They can't figure out why I don't eat patty melts and biscuits-and-gravy.
These folks are not fat for medical reasons.
Doesn't it stand to reason that people are born with certain levels of willpower about food (or in general)?
Also, you can predict someone's future weight and bmi pretty well from the time they are children or teenagers. There is a ton of research on this. One of them: https://www.ncbi.nlm.nih.gov/m/pubmed/20927643/
And, as I noted above, the people who talk to me don't generally discuss a lack of willpower. They discuss their willingness to eat things they know are bad and their unwillingness to be active. It's possible that this is all part of the hocus-pocus of cognitive science and that they're merely verbalizing a chemical predisposition, but I'm not quite so cynical about human consciousness to believe that.