Obesity and diseases
Obesity can cause the following diseases:

Diabetes
The obese patients have lots of fat tissues, this can cause an increased secretion of insulin, the result of high amount of secretion would increase the resistance of insulin and then pancreatic insufficiency, this will further induce hyperglycemia.

Hyperlipidemia, hyperuricemia and gout
They are all related to obesity.

Hypertension
It is related to the increase in the cardiac output and blood vessel pressure.

Coronary artery diseases
Hypertension, high cholesterol and diabetes caused by obesity are the main factors of causing coronary artery disease.

Cerebrovascular diseases and vascular embolism
Hypertension, high cholesterol and diabetes can all cause atherosclerosis and increase the risk of stroke. The obese patients are also easily suffered from vein embolism of the lower extremities and cause embolism of pulmonary and cerebral blood vessels.

Respiratory diseases
Hypoventilation syndrome, Obstructive Sleep Apnea Syndrome

Diseases of the digestive system
The obese patients do not only have high risk of gallstone, but also acute cholecystitis. The nonalcoholic fatty liver disease (NAFLD) can cause hepatomegaly, abnormality of the liver function, hepatitis and even cirrhosis. The obese patients are also complicated with Gastro-esophageal regurgitation disease and cause damage and deformation to esophagus.

Joints diseases
Overweight makes the joints to support more weight, and it can cause degeneration of the joints producing arthritis, especially the knee joints. The obese patients are often suffered from low back pain.

Reproductive diseases
The risk of infertility of the obese women is 30% higher than the normal weight women. They also suffer Polycystic Ovarian Syndrome more easily. Obesity can also influence the sexual function, the excess of the fat can influence the secretion of sexual hormone, causing the reduction of sexual desires and functional disorders, so the obese men have higher chance of impotence.

Dermatologic diseases
The obese patients often suffer friction dermatitis at skin folding area including neck, axilla, genitals and buttocks, causing red and itching eczema. The obstruction of the venous return of the lower extremities can also cause varicose veins and dermatitis.

Psychological diseases
The obese patients easily have Feeling of inferiority and lack of self-esteem, and even depression.

Cancer
The obese patients have higher risk of suffering colon and rectal cancer, prostate cancer, endometrial carcinoma, gallbladder cancer, ovarian cancer and breast cancer.

Body Mass Index (BMI) can also influence the mortality rate. People with higher or lower BMI have more risk of suffering diseases than those whose BMI is between 22-25, and the mortality rate is also higher. Therefore, it is very important to maintain an ideal weight.