I put on weight in the US no matter what I eat if I eat until I'm full. I naturally drift up by about a pound a year, and faster if I recently dieted. The only way to lose weight is to be constantly hungry. I will sometimes do that for a few months to get my weight under control. It then wanders back up. I've tried all sorts of diets, including plant-based, and it doesn't help. I need to be hungry all the time.
I find it easy to lose weight in less developed countries, even eating what would be considered much less healthy food in the US (fried fatty food, lots of meat, etc.). The food also tastes more, for lack of a better word, real.
I'm not sure we have any clear sense of what, in out hyper-efficient industrial food economy does this. Come to think of it, we don't even know it's the food -- could be something else environmental.
But that's how my own body behaves.