I think the causality you were trying to invoke goes "If you eat more than you need, you could become overweight." As such, it describes ways people can become overweight, not the cause for obesity or food cravings.

People are overweight for reasons other than "eating too much," just as drug addicts relapse for reasons other than "trying meth once." I'm actually comfortable thinking about greed as a symptom of a disconnected world view as well. Just one that none of the afflicted are inclined to treat.