This post is somewhat off point, but it has to do with why it is that some people don't ever seem to put on weight and others are in a constant battle to stay slim.
A NYT times article based on a new book by Gina Kolata suggests that we all have internal mechanisms that try to keep our body weight within a narrow range, and that this range is not the same across people. The way these mechanisms work is to slow down or speed up our metabolic rate depending on how much we eat. People who are naturally thin will rapidly lose weight if they put on pounds and vice a versa. Studies have shown that an individual's natural weight zone is genetically determined.
This doesn't really lead to an argument for abdicating responsibility for one's obesity --- but it does say that it's really much harder for some people to do anything about it. If we truly understood this it would affect the way we judge a person who seems more than a little bit on the heavier side. More importantly it would change the way many people judge themselves.
It is always a bit uncomfortable to talk about the fact that we all arrive with natural advantages and disadvantages but these days I see much more of it the popular science press. (The findings I just talked about are actually not recent but are only now finding their way into the NYT.)
For example, consider the more-or-less established view that men of south asian origin are much more likely than average to get heart attacks regardless of diet and where they live. Stories like this one abound. It suggests that any South Asian male who has waist bigger than 35 inches is almost certainly doomed.