When a person consumes more calories than he burns then the excess calories get stored in the form of fat causing obesity.

Genetic factors–Obesity tends to run in families. If parents are fat then the offspring also show a tendency to accumulate fat. Even the diet and lifestyle habits which are practiced in family also contribute to obesity.

Environment. – A person’s eating habits and the level of physical activities a person has also contribute for excess deposition of fat. When a person eats food containing more calories and has a sedentary work then the calories consumed are more than calories burnt. The excess amount calories are stored as fat.

Psychological disturbances.- There is a tendency to over eat in response to negative emotions like boredom, sadness or anger. This leads to obesity.

Binge eating disorder.

Diseases and conditions like Hypothyroidism, Cushing's syndrome, Depression, and certain neurological problems lead to overeating which in turn leads to accumulation of fat