Guide to Obesity: Understanding Its Causes and Risks

What is Obesity?

Obesity is an excess of body fat, which is typically defined as a body mass index (BMI) above 30.  Morbid obesity is generally defined as being 100 pounds or 100% above ideal body weight, or a BMI above 35.  According to the Centers for Disease Control and Prevention, 69.2% of American men and women over age 20 are overweight or obese, with 35.9% of adults meeting the criteria for morbid obesity. More than 18% of children and adolescents (aged 6 to 19) are obese. This problem is associated with the development of life-threatening complications such as high blood pressure, diabetes, and heart disease.

Causes of Obesity

The exact causes of morbid obesity are not understood, but there are likely many factors involved. In obese people, the set point of stored energy is too high. This altered set point may result from a low metabolism with low energy expenditure, excessive caloric intake or a combination of both. Some scientific data indicate that 80% of obesity may be inherited, strongly indicating a genetic cause. The most probable contributing factors to obesity are genetic, psychological, environmental, social and cultural influences.

Severe obesity is not caused by a lack of self control.

Health Risks of Obesity

A variety of medical problems are associated with being obese.


Noninsulin-dependent (Type 2) diabetes is highly associated with obesity. A weight gain of 11 to 18 pounds doubles a person's risk of developing type 2 diabetes compared to someone who has not gained weight. After weight loss, up to 80% of people find they no longer have symptoms or require diabetes medication. Obese patients who are not diabetic will significantly reduce their risk of developing diabetes with weight loss.

Heart Disease

With obesity, there is an increased risk for heart disease, such as heart attack, congestive heart failure, angina or chest pain, abnormal heart rhythms, and sudden death.


Obesity is a risk factor for hypertension (high blood pressure). Losing weight can often help lower blood pressure, even without the use of medications.

Infertility and complications of pregnancy

Many severely overweight women are infertile because their fatty tissue alters normal estrogen hormone levels. This causes the ovaries not to release eggs. Weight loss can significantly increase one's chances of becoming pregnant.

Obesity during pregnancy is associated with increased risk of death for both the baby and the mother. Women who are obese during pregnancy are more likely to have gestational diabetes and problems with labor and delivery.

Sleep Apnea

Sleep apnea (an interruption in breathing during sleep) is a very common and serious complication of obesity. If untreated, it can lead to heart and lung damage and, in some cases, sudden death.


Obesity is associated with an increased risk for certain types of cancer: uterine, colon, gallbladder, prostate, kidney and breast cancer.


For every 2-pound increase in weight, the risk of developing arthritis is increased by 9 to 13%.

Gastroesophageal reflux disease (GERD)

Gastroesophageal reflux disease, commonly referred to as severe heartburn or acid indigestion, is a common digestive disorder in which stomach contents regurgitate into the esophagus. It is associated with a burning sensation in the chest, and over time can cause inflammation and damage to the esophagus and occasionally to the lungs and vocal cords. Afflicting an estimated 25 million Americans, GERD has a variety of causes. Most people respond well to non-surgical measures including dietary modification, weight loss and antacid therapy; however, lasting control of symptoms is sometimes difficult to attain. In cases that do not respond to medications and lifestyle adjustments, a minimally invasive procedure known as fundoplication has impressive results.

Learn more about GERD and its treatments here.

Other important health risks

Other complications associated with obesity include 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.

The risks associated with medically severe obesity are greater than the risks associated with its surgical treatments.

Next Steps

Ready for a change? To get started with our program, call (212) 305-4000 or request an appointment online today.

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