Do you have one of those irritating friends who pushes food around her plate and says she's full after a few mouthfuls? While you're wondering whether it would be polite to ask for seconds, it must seem like she has a willpower of solid steel.
But some scientists believe willpower hasn't necessarily got much to do with it. If you can't stop eating, they say, the culprit could be your brain.
According to Australian obesity experts, in some people the part of the brain that senses you're full and tells you to stop eating can become cut off, or 'insulated' from the body.
So it may have nothing to do with willpower - rather that your brain simply isn't responding to signals from your stomach. So even though you may be full, you don't realise it.
And there's more. The researchers also suggest an 'insulated' brain cannot recognise the body's need to burn off calories - which makes it even harder for you to control your weight.
The circuits in the brain that regulate your appetite and energy expenditure begin to form when you're born. So even before you eat your first meal you could already have a tendency to put on weight.
A high fat diet doesn't help either, say the researchers, as it increases the 'insulation' that causes the problem in the first place.
Could this be another key to solving the obesity puzzle? Or is it just one more excuse for people who don't want to take responsibility for being overweight? What do you think?