It has long been assumed that obesity is inherently a result of laziness and greed, and that the sufferers themselves are always to blame for the condition. However, a wealth of research into the subject has uncovered other factors which may potentially be the causes of many people's weight problems.

Research by academics at the Imperial College London suggests that a gene known as 'GAD2' may have an important role in influencing the appetite and weight gain in human beings.

The form of GAD2 most often found in thinner people is a 'protective' form, which is known to reduce the likelihood of suffering obesity. The other form of the gene appears to increase the appetite and is most often found in overweight or obese people. In cases of the latter, GAD2 appears to increase the production of gamma-amino butyric acid; a hormone which combines with other molecules and generates a feeling of hunger. This, of course, does not force the person to eat – but does make them more inclined to do so.

There are also various illnesses and forms of medication which can stimulate the appetite and/or weight gain. Cushing's disease and hypothyroidism are known to increase the chances of excessive weight gain; and many depressives have high fat and high sugar diets, which can lead to weight gain. There are forms of medication, such as steroids and antidepressants, which are known to encourage weight gain or make weight loss more difficult.

The most common causes of weight problems, including obesity, are the most well known: high fat diets, large food portions and lack of exercise.