I personally see thin people buying the same stuff obese people buy all the time. I see thin people at fast food places and sit-down restaurants (which are usually not substantially healthier). I've seen families that live off the same food supply and one person is obese while others are thin. You can argue "the thin people must only buy those foods or go to those places sparingly", but we all know that's not really generally true either.

There is so much variation that it's hard to generalize this, but the sentiment you've expressed is a big part of the reason we can't get anywhere. People's bodies react to food differently. Obesity is not always caused by a lack of inhibition. We need to stop detesting obese people before there can be a serious solution that curbs the growing obesity trend. If "diet and exercise" were tenable solutions, we'd be seeing steadily declining obesity rates; instead, the rates continue to skyrocket worldwide (in conjunction with modernization of country's food supply, suggesting that modern processing "contaminates" food with substances that promote obesity). We need a better answer.