Some folks have genetic pre-depositions for obesity, as well as diabetes, cancers, cardiovascular disease, and on and on. I know you disagree.
Ill add this, however:
You can take your food stamp card, go to a convenience store, and walk out with a dozen donuts, a 32 oz. soda, candy bars, a big bag of chips, etc. But you cannot use it for personal hygiene products like toothpaste or toilet paper.
Government policy.