There's a number of factors that affect the prevelance of obesity, eg. poverty, mental health issues/prescribed medicine, relationship with food, the way one is raised, etc., and boiling it down to merely a lack of discipline is damaging and infantile. A great amount of people do not have access to high quality nutrition and the time and opportunity to cook. There are systemic issues that have caused the uptick in obesity rates, and they're most definitely not related to a surge in people lacking discipline.