It's a question that I've often pondered. How much is the obese person to blame for their size? Perhaps instead it could be the fault of their parents, their school or their genes? Clearly the chocolate munching, burger swallowing type is out there, but I also regularly see exasperated patients who, despite a healthy sounding diet, just keep putting on weight. Are they lying to me ("I eat nothing but chicken and salad doctor, I swear") or are they somehow different?
I, for example, despite absolutely loving my food, am not overweight. I do eat a largely healthy diet, but I'll admit to pretty big portions and fairly frequent helpings of some really bad (ie delicious) things in addition. Sticky toffee pudding and any sort of crumble with custard are my absolute favourites. I exercise a fair amount, but even if I don't (commuting for 3 hours a day for 2 years during my training gave me a chance to experiment with that), I stay pretty much exactly the same size. It seems rather unfair, although of course I'm not complaining.
There's also the issue of weight loss. Why do some people struggle so much to lose weight? I know at least one GP who believes that whatever the excuses given, failure to lose weight is purely the result of a failure in will power. Those who don't succeed just don't want it enough, or perhaps aren't trying hard enough. I suppose that when it comes down to it, he's probably often right, but it does seem clear that there are some for whom weight loss is harder than others.
So far, research has not made things any clearer. Whilst there is little doubt that genetics are at least partially implicated, we are still very much in the dark as to the mechanisms involved. Studies to date have suggested that the role played by our genes may simply be in determining our psychological and behavioural attitudes towards food. There has been little evidence to support the theories that different people metabolise calories differently, or have inherited a different basal metabolic rate.
My own belief is that the majority of our eating behaviours come directly from the families in which we have grown up. After all, our parents are the ones who fed us in those early days and it's from them that we learn our earliest eating habits. Since it's well known that an overweight child is much more likely to become an overweight adult, perhaps it's a person's upbringing that is the biggest player in determining their adult size?