I say that as an ex-obese who can now say he's 'fit'. I wouldn't pose on magazine or on Venice beach, but I'll be quite happy to go shirtless this summer for the first time in more than a decade. I'm constantly hungry, and will be all my life. I fucked up my hormones by eating too much. I don't have any food I can just eat at home. I have to prepare it before. I eat out a lot, and always place myself away from food at gatherings. Each decision I make to avoid eating, I transformed into rituals, so they aren't decisions anymore.
If I had to also stop smoking/drinking/gambling, I wouldn't have succeeded. If I had half my salary, I wouldn't have succeeded.
Obesity in men is quite hard to see/feel at first, especially since I bummed my ankles before putting on weight, so most physical diminutions I put on my accident and not my weight. When my fat showed on my chin, I was already at 34 BMI (I'm at 24 now, I've been around 26-28 for 4 years).
I also was fit as a teen, my upbringing gave me a very good support system and 'community', so my willpower is easy to refill: a good demonstration, a 1st of may, a short night/weekend in a 'ZAD' (https://en.m.wikipedia.org/wiki/Zone_to_Defend) and I'm good to go do any soul-crushing task for hours.
The introduction of fast food caused America to get fat. The introduction of Ozempic is helping America reverse that.
Neither of these changes are because the average American gained or lost willpower.
These changes are because of biological cause and effect. Fast food and Ozempic are products that hack ancient biological circuits that drive behavior. It's empirically falsifiable causality, not vague woo.
People in America are fat and depressed because of a culture of looking to blame biology for poor self control rather than take responsibility for their own behaviour. Advertising is just as much of a thing in East Asia but it doesn't have the obesity problem that the west has, because there it's regarded as a personal failing. Advertisement was just as much a thing in America 50 years ago as it is now, but people weren't fat and depressed then, because people were told to take responsibility for their diet and their state of mind.
Willpower is like a muscle, it's been proven to strengthen with use. Letting people get away with blaming advertisement, biology or whatever for their failures prevents them ever needing to develop their willpower.