The Telegraph was the first major news outlet to break this story apparently. An "aviation blog" published a picture allegedly taken by an American Airlines flight attendant to highlight the difficulty of dealing with obese passengers. It's a growing problem, no doubt, and getting larger every day.
Now, either this photo is photoshopped (if so it's a very good one), or it was taken while this guy was out of his own seats (notice the two empty ones behind the row he's in) and talking to his buddy in the middle seat in mid-flight. He isn't sitting in the seat, he's sitting on the armrest (and very uncomfortably I can add - it's a good thing he carries his own padding with him.)
There is simply no way the airplane took off with him sitting like that - there's no way he can be strapped to anything like that, and blocking the aisle that badly would simply never be allowed to happen.