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- Metabolism FAQs
- Patient Comments: Obesity - Effective Treatments
- Patient Comments: Obesity - Are You Obese?
- Find a local Internist in your town
- Obesity facts
- 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? (Is it worse to be an "apple" or a "pear"?)
- 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 over-the-counter (OTC) products?
- What is the role of surgery in the treatment of obesity?
- How can patients choose a safe and successful weight-loss program?
Quick GuideSurprising Reasons for Weight Gain
What is obesity?
The definition of obesity varies depending on what one reads. In general, overweight and obesity indicate a weight greater than what is considered healthy. Obesity is a chronic condition defined by an excess amount of body fat. A certain amount of body fat is necessary for storing energy, heat insulation, shock absorption, and other functions.
Obesity is best defined by using the body mass index. The body mass index is calculated using a person's height and weight. The body mass index (BMI) equals a person's weight in kilograms (kg) divided by their height in meters (m) squared. Since BMI describes body weight relative to height, it is strongly correlated with total body fat content in adults. An adult who has a BMI of 25-29.9 is considered overweight, and an adult who has a BMI over 30 is considered obese. A BMI of 18.5-24.9 is considered normal weight.
How common is obesity?
Obesity has reached epidemic proportions in the United States. Over two-thirds of adults are overweight or obese, and one in three Americans is obese. The prevalence of obesity in children has increased markedly. Obesity has also been increasing rapidly throughout the world, and the incidence of obesity nearly doubled from 1991 to 1998.
What are the health risks associated with obesity?
Obesity is not just a cosmetic consideration; it is harmful to one's health. In the United States, roughly 112,000 deaths per year are directly related to obesity, and most of these deaths are in patients with a BMI over 30. For patients with a BMI over 40, life expectancy is reduced significantly. Obesity also increases the risk of developing a number of chronic diseases, including the following:
- 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 insulin resistance is obesity. The pancreas initially responds to insulin resistance by producing more insulin. As long as the pancreas can produce enough insulin to overcome this resistance, blood glucose levels remain normal. This insulin resistance state (characterized by normal blood glucose levels and high insulin levels) can last for 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 insulin resistance is a pre-diabetes condition.
- 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.
- High cholesterol (hypercholesterolemia)
- Stroke (cerebrovascular accident or CVA)
- Heart attack. A prospective study found that the risk of developing coronary artery disease increased three to four times in women who had a BMI greater than 29. A Finnish study showed that for every 1 kilogram (2.2 pounds) increase in body weight, the risk of death from coronary artery disease increased by 1%. 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. Obesity has been linked 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.
- Gout and gouty arthritis
- Osteoarthritis (degenerative arthritis) of the knees, hips, and the lower back
- Sleep apnea