The main reason that whole families tend to be overweight is that they share the same eating habits. On the whole, differences are caused by environmental factors such as diet and the amount of physical activity taken. However, many researchers are trying to discover any genes that might predispose people to weight gain. For example, there is a lot of interest in leptin, a protein that travels from fat deposits to the brain, giving it information about how much fat the body has on deposit. Leptin then probably triggers chemical reactions that increase or suppress our intake of fat and influence how much more fat is deposited by the body.
Obese people have high levels of leptin in their blood.
This suggests that there may be faulty receptors in their brains so that the messages can't get through to help prevent the pounds piling on. People affected might not feel full in the same way that normal-weight people do when they have eaten. However, there is no need for them to despair - they do not have to be 'victims' of their genes. The good news is that eating habits are largely learned and can be adjusted, and more physical activity can also help. Many overweight people think they must be different to other people or think they burn fewer calories or burn their calories more slowly.