Not eating healthy or not watching what you eat can lead to obesity.
Not exercising daily can also lead to having fat but another reason could be not being strong.
Obesity is not a disease itself but it causes many other diseases like high blood pressure. Heart trouble, kidney trouble, diabetes, gout and joint pains, stroke, skin diseases and some of which may increase the rate of your death. The more a person’s weight, the greater is the risk of his early death.

Vital Organ

Obesity is not a disease but a disorder, which affects the vital organs of the human body.

Heart and Lungs

The heart is a wonderful and important organ of our body with out which there can be no life, even during our sleep, it works tirelessly. It supplies blood to your whole body. The heart is helped by the lungs to purify the blood. Lungs go on purifying the blood to be sent back to the heart.

Excess Fat

Fat is needed in our body but in limited quantities. The excess of fat leads to various disorders and diseases.
Heart muscles contract in order to pump blood, when the fat hits an overload, the heat muscles can do nothing but over work in the process of supplying blood to the tissues, causing the heart to work more.
Blood gets the nutrition from the intestines through the food we take. When the proportion of fat content exceeds the limit, the blood gets thickened and the heart muscles have to overwork in pumping the blood.

Cholesterol

Cholesterol is a normal element of the blood. It is used by the adrenal and the sex glands to form your hormones. It is found in the cell membranes and the layers of the skin. Excess cholesterol is made by saturated fats from the foods we eat. Fatty deposits holding large quantities of cholesterol lead to the thinning and hardening of the arteries. We know that the excess fat gets placed in the surface of the heart. Excess fat is also a living tissue and so it requires blood supply just as any other tissue in our body. An increase in body fat increases the number of small blood vessels for the blood supply. Overweight also interrupts the lung function, resulting in respiratory problems.

Liver and Obesity

Liver's purpose in our body is very important for its role in the metabolism of fats. Fat is needed for heat and energy in our body, the liver not only breaks the fat with the help of the digestive pancreatic juice from the pancreas, but also converts the excess carbohydrates into fat for storage. When an individual takes in more calories than are required they are stored as fat, even if obtained from carbohydrates or proteins. When fat is required for energy it is moved from this storage and carried to the liver, to be split into substances and be used as energy.

Kidney and Obesity

Kidneys are organs of removal of waste products from the body. There are two kidneys and are located on either side of the lower spine. Kidneys have a lot of supply of blood vessels. It has fine filters and performs the job of filtering twice the amount of blood in the body every hour. It does not allow the large particles of essential proteins and red cells to pass through the filter.
More fat tissues the body contains, the greater the task of removal. For a person with excess fat, kidney diseases tend to develop easily.

Muscles and Joints Pain

Excess weight interferes with the skeletomuscular. All the weight “lifting” joints are over worked due to the excess weight. Rheumatism, gout and arthritis are common in those who are obese.