All of the overly fat people that I know love, I mean LOVE bread. They can sit at a table and consume half a loaf of bread before they even look at the rest of the meal. The three that expressed a desire to lose weight successfully did so by severely reducing their bread intake then reducing their quantity intake of high carb vegetables.
Nonetheless, some obesity and diabetes is not caused by overeating. Instead, some obesity is caused by diabetes despite not overeating.