Obesity

Content provided by the Faculty of the Harvard Medical School

Obesity

What Is It?

Obesity is an excess of body fat, and it's one of the most common health problems in the United States. About one-third of all American adults are considered to be obese. Obesity is measured using a scale called a body mass index, or BMI, which is calculated using your weight and height. A BMI higher than 30 is classified as obese.

Obesity affects both adults and children. Approximately 9 million (about 15%) of American children aged 6 to 17 are obese, a percentage that has doubled since the 1960s.

Obesity can shorten your life and put you at risk of developing a number of conditions, such as high blood pressure, diabetes, heart disease and some forms of cancer. Many other health risks are higher for people who are obese, and the risks may increase as the degree of obesity increases. People who carry extra weight around their waist, rather than in their legs and thighs, may be more likely to experience health problems caused by obesity.

People become obese for a number of reasons. Often, several of these factors are involved. Some of the most common reasons for obesity are:

• Genetic influences — Your genetic makeup plays a significant role in how likely it is that you will become obese. However, you still maintain most of the control when it comes to your weight, unless you have one of some rare genetic diseases that make it almost impossible to avoid obesity.

• Physiological influences — Some researchers believe that every person has a specific "set point" for body weight — a predetermined weight that the body resists moving away from. Also, people of the same age, sex and body size often have different metabolic rates, meaning their bodies burn food differently. Someone with a high metabolic rate may require more calories to maintain approximately the same body weight as someone whose metabolic rate is low.

• Food intake and eating disorders — If you eat a lot, especially foods that are high in fat and calories, you can become obese. Obesity also can result from eating disorders, such as night-eating syndrome or a tendency to binge.

• Lifestyle — If you lead a sedentary life, in which you sit most of the time and do not exercise, you are at a higher risk of becoming obese.

• Your weight history — If you were overweight as a child or as an adolescent, you are more likely to be obese as an adult.

• Pregnancy — Pregnancy can contribute to obesity. About 15% of women weigh 20 pounds more after each pregnancy.

• Drugs — Some drugs can cause obesity. The most common drugs associated with obesity are steroid hormones and drugs used to treat psychiatric conditions.

Symptoms

The primary sign of obesity is an above-average body weight. If you are obese, you may also experience:

• Trouble sleeping

• Sleep apnea (a condition in which breathing is irregular and periodically stops during sleep)

• Easily getting short of breath

• Varicose veins

• Skin problems caused by moisture that accumulates in the folds of your skin

• Gallstones

• Osteoarthritis in weight-bearing joints, especially the knees

Obesity has also been linked to high blood pressure, as well as to high levels of blood sugar (diabetes), cholesterol and triglycerides.

Diagnosis

Obesity is diagnosed by calculating your body mass index (BMI). BMI is calculated using your height and weight. A BMI of 30 or more defines obesity. In general, this means your body weight is 35% to 40% more than your ideal body weight. Body shape is also important. People who carry most of their weight around the waist (apple shaped) have a greater risk of heart disease and diabetes than people with big hips and thighs (pear shaped).

Your body fat also can be calculated by using skin calipers, an instrument that measures the thickness of your skin. Waist circumference is a good measure of the more dangerous abdominal obesity. Women with a waist more than 35 inches or men with a waist more than 40 inches are at increased risk.

Expected Duration

Obesity is often a lifelong problem. Once excess weight is gained, it is not easy to lose. And once you do lose weight, you will have to work at maintaining your healthier weight. The length of time it takes to reach your weight goal depends on how much you have to lose, your activity level and the type of treatment or weight-loss program you choose. Diseases and conditions caused by obesity often improve as you lose weight.

Prevention

To prevent obesity and maintain a healthy body weight throughout life, eat a well-balanced diet and exercise regularly. Preventing obesity is important because once fat cells form, they remain in your body forever. Although you can reduce the size of fat cells, you cannot get rid of them.

Treatment

Weight reduction is achieved by consuming fewer calories and increasing activity and exercise.

Structured approaches and therapies to reduce weight include:

• A modified diet — A reasonable weight loss is one to two pounds weekly, which can usually be achieved by eating 500 to 1,000 fewer calories daily. For adults who use alcohol, eliminating 12 ounces of beer or 5 ounces of wine can cut 100 to 150 calories per day. Whether you concentrate on eating less fat or fewer carbohydrates is a matter of personal choice. Fats have more than twice as many calories per ounce than carbohydrates or protein. If you cut out carbohydrates, you still need to limit fat and choose healthy fats, such as monosaturated and polyunsaturated oils.

• Regular exercise — U.S. health experts currently recommend at least 30 minutes of moderate physical exercise daily, such as walking. Add more activity during the day by taking the stairs and getting up often from your desk.

• Nonprescription diet pills — In general, over-the-counter diet pills contain ingredients that can increase heart rate and blood pressure. It is not clear how effective they are in producing weight loss that can be maintained over time. Common side effects include feeling jittery and nervous, and having heart palpitations. Over-the-counter diet pills containing phenylpropanolamine have been taken off the market because this ingredient was associated with an increased risk of stroke. Diet pills with other ingredients also may elevate blood pressure, and some experts believe they may be associated with an increased risk of stroke.

• Prescription diet pills — These include orlistat (Xenical), which decreases the absorption of dietary fat by 30%; amphetamine derivatives; and sibutramine (Meridia). To help you lose weight, your doctor may prescribe medications along with a calorie-restricted diet. However, almost all people regain the weight when they stop using the medication. The effects of long-term use of these drugs have not been determined.

• Surgery — If obesity is severe (a BMI greater than 40), doctors may recommend a surgical procedure to limit the amount of food the body can digest. One procedure is called gastroplasty, also known as stomach stapling. A surgeon creates a small pouch in the stomach that allows only limited amounts of food to be eaten at one time.

When To Call A Professional

Call your doctor if you need help losing weight, or if you have any of the symptoms or complications of obesity.

Prognosis

Some people are successful at losing weight and keeping it off. Others, however, find it difficult to maintain the weight loss for long. Most patients return to their pretreatment weight within five years.

Additional Info

American Dietetic Association 216 W. Jackson Blvd. Chicago, IL 60606-6995 Phone: (312) 899-0040 Toll-Free: (800) 877-1600 http://www.eatright.org/

National Heart, Lung and Blood Institute (NHLBI) 6701 Rockledge Dr. P.O. Box 30105 Bethesda, MD 20824-0105 Phone: (301) 592-8573 http://www.nhlbi.nih.gov/

Centers for Disease Control and Prevention (CDC) 1600 Clifton Rd., NE Atlanta, GA 30333 Phone: (404) 639-3534 Toll-Free: (800) 311-3435 http://www.cdc.gov/

Center for Food Safety and Applied Nutrition U.S. Food and Drug Administration (FDA) 5100 Paint Branch Parkway College Park, MD 20740-3835 http://vm.cfsan.fda.gov/

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Last updated:	August 22, 2007