Comment by paulpauper

I don't think it's a s simple as inactivity. IF this were true, then being active would reverse the weight gains, but it does not, at least not for me and others. I was still as active in my 30s as I was in my late teens and 20s but still gained weight. Likewise, gyms are full of people in their 30s and 40s who are not losing weight despite regular attendance. Despite the popularity of fitness apps, people keep getting fatter. It is only GLP-1 drugs that has put some dent in obesity rates. I think metabolism or some other biological, non-environmental variable plays some role. Or some reduction of NEAT that cannot be explained by careers.