The one tonne man was having to eat 15,000 calories a day simply to maintain his weight. If he ate anything less than that he would lose weight. This is the equivalent of 15 pizzas a day.
And still he wouldn't admit to over eating and maintained that he only ate the same as everyone else.
While genetics may make you want to over eat, they can't make the weight go on unless you actually put the food in your mouth (and i speak as someone over weight myself....I know what to do about it, and really only have myself to blame)