This can't possibly be true. A caloric surplus of 500cal/day adds a pound of weight per week. That'd mean in a decade of life the _average_ American would add an additional 260 pounds. In 4 decades Americans would add half a ton to their waistline, on average.
That'd mean at then end of their life the average American would die weighing over 2 tons
Additionally the fatter you are the more calories you use at rest. So there's a point where if you consistently eat too much you'll stop gaining weight.
The biggest source of error here will be the calories in the garbage bin though. I wouldn't be surprised if a lot of this is stored in the waste disposal, not the waist disposal.
Once you're 140kg, a sedentary lifestyle requires you to take something like 800 more calories as the same person with the same lifestyle at 70kg, to each maintain your weight.
So excess eating of 500 calories over what a normal bodyweight (say 70kg) needs to maintain, leads to fat people (say 110kg) who at some point stop gaining weight and stay at that fat level (of say 110kg).