The study is too extreme. You cannot put someone on a 600 calorie diet and expect them to maintian a low weight. It must be done gradually. It is terribly similar to training. You cannot take a new cyclist and put them on the same training schedule as a ProTour team.
If obesity is so genetic then tell me why the mean European is so much thinner than the mean American. Tell me why I, at 130lbs and 5'9" can sometimes wear a medium pro-cut jersey?

In my opinion, this 'study' was conducted so a scientist could tell fat people it is ok to be fat and there is nothing to be done about it.