Obesity

Medical Author: Ruchi Mathur, MD
Medical Editor: Dennis Lee, MD

• What is obesity?
• How common is obesity?
• What are the health risks associated with obesity?
• What causes obesity?
• What are other factors associated with obesity?
• How is body fat measured?
• What about weight-for-height tables?
• What is the body mass index (BMI)?
• Does it matter where body fat is located?
• What can be done about obesity?
• What is the role of physical activity and exercise in obesity?
• What is the role of diet in the treatment of obesity?
• What is the role of medication in the treatment of obesity?
• What about herbal fen/phen?
• What about meal substitutes, artificial sweeteners, and OTC products?
  • Meal substitutes
  • Artificial sweeteners
  • Over-the-Counter (OTC) weight loss products
  • Phenylpropanolamine
• What is the role of surgery in the treatment of obesity?
• What is new in obesity research?
• Choosing a safe and successful Weight-Loss Program
• Review of popular weight-loss diets
  • The Atkins Diet
  • The Carbohydrate's Addict's Diet
  • The Pritikin Principle
  • Protein Power Lifeplan
  • Sugar Busters
  • Suzanne Somers' Get Skinny on Fabulous Food
  • The Zone Diet
• Obesity At A Glance
• Related BMI calculator articles:
  BMI calculator - on WebMD
• Related obesity articles:
  Obesity - on WebMD

What is obesity?

The definition of obesity varies depending on what one reads, but in general, it is a chronic condition defined by an excess amount body fat. A certain amount of body fat is necessary for storing energy, heat insulation, shock absorption, and other functions. The normal amount of body fat (expressed as percentage of body fat) is between 25-30% in women and 18-23% in men. Women with over 30% body fat and men with over 25% body fat are considered obese.

How common is obesity?

Obesity has reached epidemic proportions in the United States. One in three Americans is obese. Obesity is also increasing rapidly throughout the world, and the incidence of obesity has nearly doubled form 1991 to 1998.

What are the health risks associated with obesity?

Obesity is not just a cosmetic consideration; it is a dire health dilemma directly harmful to one's health. In the United States, roughly 300,000 deaths per year are directly related to obesity, and more than 80% of these deaths are in patients with a BMI (body mass index, which will be discussed later in this article) over 30. Obesity also increases the risk of developing a number of chronic diseases including:

• Insulin Resistance. Insulin is necessary for the transport of blood glucose (sugar) into the cells of muscle and fat (which is then used for energy). By transporting glucose into cells, insulin keeps the blood glucose levels in the normal range. Insulin resistance (IR) is the condition whereby the effectiveness of insulin in transporting glucose (sugar) into cells is diminished. Fat cells are more insulin resistant than muscle cells; therefore, one important cause of IR is obesity. The pancreas initially responds to IR by producing more insulin. As long as the pancreas can produce enough insulin to overcome this resistance, blood glucose levels remain normal. This IR state (characterized by normal blood glucose levels and high insulin levels) can last years. Once the pancreas can no longer keep up with producing high levels of insulin, blood glucose levels begin to rise, resulting in type 2 diabetes, thus IR is a pre-diabetes condition. In fact scientists now believe that the atherosclerosis (hardening of the arteries) associated with diabetes likely develops during this IR period.

• Type 2 (adult-onset) diabetes. The risk of type 2 diabetes increases with the degree and duration of obesity. Type 2 diabetes is associated with central obesity; a person with central obesity has excess fat around his/her waist, so that the body is shaped like an apple.

• High blood pressure (hypertension). Hypertension is common among obese adults. A Norwegian study showed that weight gain tended to increase blood pressure in women more significantly than in men. The risk of developing high blood pressure is also higher in obese people who are apple shaped (central obesity) than in people who are pear shaped (fat distribution mainly in hips and thighs).

• High cholesterol (hypercholesterolemia)

• Stroke (cerebrovascular accident or CVA)

• Heart attack. The Nurses Health Study found that the risk of developing coronary artery disease increased 3 to 4 times in women who had a BMI greater than 29. A Finnish study showed that for every one kilogram (2.2 pounds) increase in body weight, the risk of death from coronary artery disease increased by one percent. In patients who have already had a heart attack, obesity is associated with an increased likelihood of a second heart attack.

• Congestive heart failure

• Cancer. While not conclusively proven, some observational studies have linked obesity to cancer of the colon in men and women, cancer of the rectum and prostate in men, and cancer of the gallbladder and uterus in women. Obesity may also be associated with breast cancer, particularly in postmenopausal women. Fat tissue is important in the production of estrogen, and prolonged exposure to high levels of estrogen increases the risk of breast cancer.

• Gallstones

• Gout and gouty arthritis

• Osteoarthritis (degenerative arthritis) of the knees, hips, and the lower back

• Sleep apnea

• Pickwickian syndrome (obesity, red face, underventilation, and drowsiness)

Next: What causes obesity? »

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Last Editorial Review: 7/22/2003