Causes of obesity

                              Obesity is generally caused by eating too much and moving too little.

Many factors influence body weight—genes, though the effect is small, and heredity is not destiny; prenatal and early life influences; poor diets; too much television watching; too little physical activity and sleep; and our food and physical activity environment.

Inactivity.

 If you're not very active, you don't burn as many calories. With a sedentary lifestyle, you can easily take in more calories every day than you use through exercise and normal daily activities. Lack of physical activity is another important factor related to obesity. Many people have jobs that involve sitting at a desk for most of the day. They also rely on their cars, rather than walking or cycling.When people relax, they tend to watch TV, browse the internet or play computer games, and rarely take regular exercise.If you are not active enough, you do not use the energy provided by the food you eat, and the extra energy you consume is stored by the body as fat.The Department of Health recommends adults do at least 150 minutes of moderate-intensity aerobic activity, such as cycling or fast walking, every week. This doesn’t need to be done in one go, but can be broken into smaller periods. For example, you could exercise for 30 minutes a day for five days.

Unhealthy diet and eating habits.

 Having a diet that's high in calories, lacking in fruits and vegetables, full of fast food, missing breakfast, and laden with high-calorie beverages and over sized portions all contribute to weight gain.
eating large amounts of processed or fast food that is high in fat and sugar
drinking too much alcohol – alcohol contains a lot of calories, and people who drink heavily are often overweight
eating out a lot – you may be tempted to also have a starter or dessert in a restaurant, and the food can be higher in fat and sugar
eating larger portions than you need – you may be encouraged to eat too much if your friends or relatives are also eating large portions
drinking too many sugary drinks – including soft drinks and fruit juice
comfort eating – if you feel depressed or have low self-esteem, you may eat to make yourself feel better

Pregnancy.

 During pregnancy, a woman's weight necessarily increases. Some women find this weight difficult to lose after the baby is born. This weight gain may contribute to the development of obesity in women.

Lack of sleep.

 Too little sleep can cause changes in hormones that increase your appetite. You may also crave foods high in calories and carbohydrates, which can contribute to weight gain.

Certain medications.

 Some medications can lead to weight gain if you don't compensate through diet or activity. These medications include some  anti-seizure medications, diabetes medications,antidepressants, antipsychotic medications, corticosteroids and beta blockers. 

Medical problems

. Obesity can sometimes be traced to a medical cause, such as  Cushing's syndrome,Prader-Willi syndrome and other diseases and conditions. Some medical problems, such all kind of arthritis, can lead to decreased activity, which may result in weight gain. A low metabolism is unlikely to cause obesity, as is having low thyroid function.