For some obese people, genetic factors play a part in their excess weight. A lot of research has been carried out into genetic factors that might be linked to obesity. In 1990, a Canadian scientist, Professor Claude Bouchard, published a study with very interesting results. Twelve pairs of identical twins were overfed by an amount of 1000 kilocalories per day for three weeks.

All of the participants gained weight during this period, but there were huge differences between the different pairs of twins. However, each individual reacted in exactly the same way as their identical twin.

A few years later, in 1994, researchers became very excited when the gene responsible for obesity in mice was discovered. This gene forms a protein called leptin which contributes to the feeling of fullness after eating. It was shown that mice with a mutated gene consumed huge amounts of food.

However, it soon became clear that the excitement was premature and that human beings do not react in that way. So far, there is no proof that obese people display an anomaly in this gene. So this cannot explain obesity. However, these studies have led to new insights into a variety of bodily mechanisms: we know that in obese people, fat-burning, metabolism, and feelings of hunger and of fullness no longer function normally.