Again, even those with extensive and expensive outside support see depressingly poor outcomes on average, though of course that does improve things somewhat. Those are still a ton worse than GLP-1 agonists, as far as efficacy. And that's the very best effort we've got for "diet and exercise" interventions, short of live-in dietitians and chefs and personal trainers or putting people in total institutions.
Meanwhile, people move from a skinnier country to a fatter one and usually get fatter. Willpower wasn't what was keeping them skinnier. It makes no sense to expect willpower to be what'll make the fatter country skinnier when that doesn't seem to be why skinnier countries are skinnier.
When talking about human society, environment is a culmination of collective choice.
People who say willpower is futile are still faced with choice of if they feed their kids soda and McDonalds for breakfast.
To change my lifestyle meant somehow incorporating all the good behaviors I wanted to do but within the limitations of being me. It took a lot of work. I carefully measured my caloric intake (gram scale all the things) and expenditure (fitness watch with optical HR, fancy schmancy scale that does body fat estimation) plus doing things like: always taking the stairs, combine my morning run/cycle with my commute (shower at the office), taking the longer way, etc. Dropped 40kg. Went from couch to running half-marathons and cycling centuries. I had to completely change my relationship with food and study all of the nutrition stuff that was never taught to me. I had to unlearn habits instilled by my parents (emotional eating, boredom eating) which meant finding different ways to deal with stress and relieve boredom. ADHD is a bitch. And weed is awesome. Learning how to accommodate munchies without putting on weight also requires forethought.
No. It really isn't all that realistic for everyone to do what I did much less have the same privileges and opportunities. I had to treat my body like a biologist studying a critter. I was incredibly lucky to be at the right spot in my life where I hit a glass ceiling at work and had so much fuck you energy pent up from feeling out of control of my life. I chose to exert maximum control over my body in order to cope and prove something.
It was a monumental amount of effort over a two year period. It is extremely unrealistic to ask people to use a gram scale for their food consistently. Or to log/track their food intake for every bite. Or to always monitor their heart rate to estimate/track your caloric output. Hyper monitoring your body is a weird hobby.
I really do think instead we should be legislating and regulating food more strictly. Labeling isn't really enough. Food science is being weaponized, much like psychology has been with advertising. We shouldn't allow that kind of manipulation for profit.