Some people don't lose weight as easily as others, due to genetics, medical treatment, disability... And even some others have the freedom to not invest as much effort on losing weight.

Point being: there are overweight Japanese, despite the existence of the measures Japan takes to avoid it. These are the people I mean that it doesn't work for. And for those people, they don't have to deal only with the consequences of being overweight, they also have to deal with being treated very poorly. You can say it's for their own good, and the it incentives them to better themselves. Regardless, it still sucks for them.

Shaming people into losing weight may work, on aggregate. I'm not entirely convinced it's a good way to go about it, at the individual level.

Let's be generous and say that a person's body runs on 1600kcal/day, which is pretty low and the other 1800kcal/day which is kinda average. The difference in weight loss between these two over six months eating and exercising is negligible. The maths just doesn't math.

But to be fair It may be psychological. Eating is a very common coping mechanism and not taking care of your body is a common symptom of stress and depression.