[cecilpl2]

While you are not wrong about self-discipline being an important factor, there are also genetic components to things like ghrelin and leptin levels and responsiveness.

Not to mention also that the willpower to override your habits is a limited resource and not everyone has the ability to apply it to this aspect of their lives.

[ac29]

The genetics of the human population have not shifted nearly as fast as weights have increased. Genetics may play some role in weight, but other factors are far more determinant.