Many serious medical problems can arise if you are obese. These include:

High blood pressure (hypertension) :

This is a condition where your blood pressure increases above the normal range. If you put on weight, you increase the amount of fatty tissue and this causes an increase in demand for oxygen and nutrients, leading to an increased circulation and hypertension. Weight gain also increases the level of insulin in your blood and causes sodium and water to be retained, thereby increasing the blood volume. Furthermore, excess weight causes an increase in your heart rate and a reduction in the capacity of blood vessels to transport blood and this contributes to the raised blood pressure.

Diabetes :

One of the leading causes of type 2 diabetes is obesity. Increased fat deposition makes your body resistant to insulin, and the increased insulin resistance makes you vulnerable to diabetes. Two main areas that contribute to this resistance include the liver and the muscles.

Abnormal blood fats :

Obesity is also associated with altered levels of body lipids. Levels of low-density lipoprotein (LDL), the bad form of cholesterol, are elevated; levels of high-density lipoprotein (HDL), the good form of cholesterol, are reduced, and triglycerides (TG) reach high levels. These abnormal blood fats can, over the time, contribute to atherosclerosis, which is a buildup of fatty deposits in arteries throughout your body. This puts you at risk for coronary artery disease and stroke.

Coronary artery disease :

This also results from the buildup of fatty deposits in the arteries that supply your heart. This causes them to become narrow and decreases blood flow to your heart. Diminished blood flow to your heart causes chest pain (angina) and complete blockage can lead to a heart attack.

Stroke :

Because obesity is associated with atherosclerosis, the arteries of the brain are also involved. If a blood clot forms in a narrowed artery in your brain, this can cause a stroke.

Osteoarthritis :

These joint disorders most often affect the knees, hips and lower back. The excess weight puts pressure on these joints and wears away the cartilage that protects them, resulting in joint pain and stiffness.

Sleep apnea:

This is one of the most common consequences of obesity. This is a serious condition that causes a person to stop breathing for short periods during their sleep, to snore heavily, and to wake up in the middle of the night gasping for air because the upper airway get blocked during sleep. Most people with sleep apnea are overweight, which contributes to a large neck and narrowed airways.

Cancer :

Many studies show an increased risk of some cancers in the overweight and obese: i.e., cancers of the colon, rectum, esophagus, kidney, breast and prostate. see also Obesity and Cancers

Fatty liver disease :

As a consequence of being over weight or obese, excess fat stores build up and have a tendency to deposit in the liver. These fatty accumulations lead to inflammation and scarring of the liver – a condition called cirrhosis of the liver.

Gallbladder disease :

Overweight people tend to produce more cholesterol as a result of their altered lipid content and they are therefore at increased risk of forming gall stones and having gall bladder disease.

Fertility and pregnancy problems :

Increased body mass has also been shown to be associated with fertility problems for both men and women. It may also lead to the development of gestational diabetes and other pregnancy related problems including an increase in the risk of birth defects.