Article updated and reviewed by Hubert Chen, MD, Associate Director of Medical Sciences, Amgen Inc. and Assistant Professor of Clinical Medicine University of California, San Francisco on July 8, 2005.
Obesity refers to an increase in total body fat. The easiest and most widely accepted method of determining whether you are obese is by measuring your Body Mass Index, or BMI. To calculate your BMI, follow these steps:
1. Multiply your weight in pounds by 705; divide by your height in inches; divide this number by your height in inches a second time.
2. You may also use an online BMI calculator at the National Heart, Lung, and Blood Institute. Go to http://www.nhlbisupport.com/bmi/.
A normal BMI = 18.5-24.9; overweight = 25.0-29.9; obese = 30 or greater; and morbidly obese = 40 or greater.
Why Should I Care About Obesity?
Obesity has become an epidemic in the U.S. and other developed countries. As many as one-third of all Americans are obese based on the BMI criteria. In addition to body image issues, obesity causes significant health issues. It is the second leading cause of preventable death (after smoking), and is associated with type 2 diabetes, hyperlipidemia, coronary artery disease, arthritis, gallstones, and certain types of cancer.
Often referred to as a disease, obesity is actually a sign of what may well be a spectrum of different kinds of disorders – genetic or environmental. In fact, there is no single definition of obesity. It may be simply an extreme degree of overweight - but a person can be overweight without being obese. A 250-pound, 6' linebacker, for example, may be overweight according to ordinary standards, but may actually have a below-average amount of body fat. In contrast, a person in a normal weight range but with very sedentary habits, could have a small muscle mass, be storing excess fat, and thus be classifiable as obese.
About one-half of all Americans are above their ideal weight, as determined by standard tables, and for the majority of them, the excess weight is in the form of body fat, not muscle mass. Of this group, half exceed their ideal weight by 20 percent or more. Hence, they are classified as obese.
Obesity has become epidemic in the U.S. and other developed countries. More than 58 million Americans are overweight, and that includes at least 1 in 5 children.
Two principal risk factors that lead to obesity, poor nutrition and lack of physical activity combined, are the second leading cause of preventable death (tobacco is first). Obesity is associated with significant increases in risk for type II diabetes mellitus, hyperlipidemia, high cholesterol, coronary artery disease, degenerative joint disease and psychosocial disability. Certain cancers - colon, rectum and prostate in men; uterus, biliary tract, breast and ovary in women - are more prevalent in the obese.
Until recently, obesity was considered the result of a sedentary lifestyle and the chronic ingestion of excess calories. This may be the principal factor for many individuals, but there is evidence of strong genetic, metabolic, and environmental influences in the development of obesity. Certain illnesses, such as Cushing’s syndrome or hypothyroidism, and medications, such as glucocorticoids, can also cause obesity. However, less than one percent of all obese patients have an identifiable secondary cause of obesity.
A physical examination, including a measurement of weight and height, is usually sufficient to diagnose obesity. A complete medical history, including age of onset, family history, eating and exercise behavior, smoking, alcohol use, and previous weight loss experience are all important.
Your physician may order blood tests, including fasting levels of glucose, cholesterol and triglycerides, to determine whether any obesity-related conditions are present.
Successful programs for weight loss reduction and maintenance should be started and followed under the care of a physician and/or a nutritionist. A weight-loss program may include:
- Exercise (the Surgeon General has called for 30 minutes of physical activity on most days of the week)
- A low-fat, high-complex carbohydrate, high fiber diet
- Behavior modification to change eating behavior
- Social support
Although several diets (such as Atkins or South Beach) have become quite popular as effective ways of losing weight, none of them has been proven to be vastly superior in rigorously conducted, large-scale clinical trials. The key (and only) reason for the success of any dietary plan is that it make you consume fewer calories than what you are expending.
It is very important to discuss all medications you are taking with your physician.
Current guidelines recommend drug treatment for individuals, especially those with other obesity-related health conditions, who have failed to respond adequately to dietary and behavioral modifications. A limited number of medications are available for the treatment of obesity. Concerns about side effects have diminished enthusiasm for appetite-suppressant drugs, particularly fenfluramine, which carry serious risks and have been withdrawn from the market. Individuals who have taken either should be evaluated by a physician.
Phentermine remains available, but is approved only for short-term use. Sibutramine (Meridia) is approved for longer-term use, but may cause an increase in blood pressure and should be used with caution and only with regular medical monitoring.
Orlistat (Xenical) is a medication that blocks the absorption of dietary fat and is also approved for longer-term use. However, it causes unpleasant side effects (greasy stool), and you also need to supplement your diet with fat-soluble vitamins.
Although surgery (such as gastric bypass) is the last resort for the treatment of obesity, it can be extremely effective. However, it should be performed at an experienced surgical center, because such operations can carry significant risks, especially in the post-operative period. Consensus recommendations are to limit surgical therapies to patients with morbid obesity (BMI > 40).
I've always been overweight. Why should I worry about it now?
Should I consider taking a medication for my weight condition?
What effect will continuing to be overweight have on my newly acquired diabetes (if applicable)?
What types of physical activity would you recommend?
How can I find the time, social support and motivation to become more physically active?
Do you recommend a specific diet?
If so, what kind?
I've lost weight before and regained it. How do I lose weight and keep it off now?
Should I consider surgery?
Editorial review provided by VeriMed Healthcare Network.