A variety of medical problems are associated with being obese. The risks associated with medically severe obesity are greater than the risks associated with its surgical treatments.

Diabetes:
Non-insulin-dependent diabetes is highly associated with obesity. A weight gain of 11 to 18 pounds increases a person's risk of developing type 2 diabetes to twice that of individuals who have not gained weight. Obese patients who are not diabetic will significantly reduce their risk of developing diabetes with weight loss.
 
Heart Disease:
There is an increased risk for heart disease, such as heart attack, congestive heart failure, angina or chest pain, sudden death and abnormal heart rhythms.
 
High blood pressure/Hypertension:
Hypertension is also a risk factor of obesity. Losing weight is one of the primary recommendations for individuals with high blood pressure.
 
High cholesterol:
High levels of "bad-cholesterol" and low levels of "good cholesterol" is very common in individuals with severe obesity. These cholesterol abnormalities increase the risks of heart disease , strokes and paralysis. Weight loss and regular exercise is critical for prevention of these life threatening complications.
 
Menstrual Irregularities:
Many overweight adolescents and young women have irregular periods or do not get their periods for months. This may be associated with excess body hair because of a condition called Polycystic Ovarian Syndrome (PCOS). PCOS is strongly associated with excess weight gain and is reversible with weight loss.
 
Sleep Apnea:
Sleep apnea (gaps in breathing during sleep) is a very common and serious complication of obesity. It can become so serious that heart and lung damage or sudden death can result.
 
Cancer:
Obesity is associated with an increased risk for certain types of cancer: uterine, colon, gall bladder, prostate, kidney and breast cancer.
 
Arthritis:
For every 2-pound increase in weight, the risk of developing arthritis is increased by 9 to 13%.

Other important health risks

Gastroesophageal reflux or severe heartburn, urinary incontinence, venous problems of the legs, lower back pain, and disability from degenerative arthritis and disk disease have also been linked to being severely overweight. Other problems, including joint pain and hypoventilation, or shortness of breath, are significantly improved or reversed by weight loss.