Which studies? I find it hard to imagine that it has been proven that for most people having a low-carb unprocessed meal once a day, no alcohol, and 5-mile daily hikes as the original poster does would would not eliminate sever weight issues.

There are clearly minority of people who can only achieve weight loss using drugs but for most people they can achieve the same effect by a lifestyle change, has this been proven incorrect?

I think the best empirical result for this is to compare US with any other western country (say Japan or France) or even US states with each other, clearly lifestyle plays a huge role in obesity.

> There are clearly minority of people who can only achieve weight loss using drugs but

Are you suggesting there are people who can burn more energy than they ingest for a prolonged period of time and not lose weight?

That… would fundamentally rewrite everything we know about how mammals consume energy.

Of course not. Nobody needs drugs to lose weight, they need to consume less energy than they use.

No for example they might have severe food addiction that it makes it hard for them to reduce food consumption otherwise.