“Not stuffing your face “ works and its free. Or a variant, don’t stuff your face with high sugar, high carb, calorie dense items.
Combine it with “moving around a bit” and its even more effective. And that is free too.
Because eating reasonably well, and moderate exercise would be like you know, ridiculous.
Don’t forget the other benefits of your advice. Less money spent on food, eating healthier foods, less fat, (obesity has been associated with cardiac disease, certain cancers, less trips to the wrapper, can wear your older clothes(when we were skinnier)....less medicines....win all around..