Hmm I think that for a lot of people, it wasn’t a choice to get fat. I know a lot of kids who are already obese and they aren’t even in their teens.
However, I do think it’s a choice once you’ve realized it and have the ability to actually do something about it.
Kinda related but unrelated: it irks me when someone comments how easy it is for me to be skinny, bc it isn’t. As a previously underweight person, I think gaining and losing weight are just as hard. I had to control my diet, work out, and have a lot of self control to not lose the habits I was building. I folded and stagnated a lot, and yeah it was demotivating but I still had to make a choice to keep going.