How much food are obese people actually eating a day?

Far more than they claim to be eating or think they are consuming. It only takes an extra 200 calories a day (a small handful of nuts or so) to be up 100 pounds after a few years. And most obese people eat far more above their caloric needs than that.

No matter what people claim, in the end losing or gaining weight is just energy in, energy out. Everything else is just details.