UnderstandingAdult ObesityWIN Weight-control Information NetworkToday, more than 65 percent of adults in the United States are “Obesity” specifically refersoverweight or obese. Obesity puts people at increased risk forchronic diseases such as heart disease, type 2 diabetes, high blood to an excessive amount ofpressure, stroke, and some forms of cancer. body fat. “Overweight”The large number of people with obesity and the serious health risks refers to an excessivethat come with it make understanding its causes and treatmentcrucial. This fact sheet provides basic information about obesity: amount of body weightWhat is it? How is it measured? What causes it? What are the health that includes muscle, bone,risks? What can you do about it? fat, and water. As a rule,What is obesity? women have more body“Obesity” specifically refers to an excessive amount of body fat. fat than men. Most health“Overweight” refers to an excessive amount of body weight that care professionals agreeincludes muscle, bone, fat, and water. As a rule, women have morebody fat than men. Most health care professionals agree that men that men with more thanwith more than 25 percent body fat and women with more than 30percent body fat are obese. These numbers should not be confused 25 percent body fat andwith the body mass index (BMI), however, which is more commonly women with more thanused by health care professionals to determine the effect of bodyweight on the risk for some diseases. 30 percent body fat are obese. These numbersHow is obesity measured? should not be confusedMeasuring the exact amount of a person’s body fat is not easy. The mostaccurate measures are to weigh a person underwater or in a chamber that with the body mass index,uses air displacement to measure body volume, or to use an X-ray test however, which is morecalled Dual Energy X-ray Absorptiometry, also known as DEXA. Thesemethods are not practical for the average person, and are done only in commonly used by healthresearch centers with special equipment. care professionals toThere are simpler methods to estimate body fat. One is to measure the determine the effect ofthickness of the layer of fat just under the skin in several parts of thebody. Another involves sending a harmless amount of electricity through body weight on the riska person’s body. Results from these methods, however, can be inaccurate for some diseases.if done by an inexperienced person or on someone with extreme obesity.
BMI (Body Mass Index) SOURCES • George Bray, M.D., Pennington Biomedical Research Center. • National Heart, Lung, and Blood Institute’s Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults: The Evidence Report. Weight in Pounds**Because measuring a person’s body fat is difficult, Two people can have the same BMI but differenthealth care professionals often rely on other means body fat percentages. A bodybuilder with a largeto diagnose obesity. Weight-for-height tables, used muscle mass and low percentage of body fat may have the same BMI as a person who has more bodyfor decades, have a range of acceptable weights for a fat. However, a BMI of 30 or higher usuallyperson of a given height. One problem with these indicates excess body fat.tables is that there are many versions, all with The BMI table above provides a useful guideline todifferent weight ranges. Another problem is that check your BMI. First, find your weight on thethey do not distinguish between excess fat and bottom of the graph. Go straight up from thatmuscle. According to the tables, a very muscular point until you come to the line that matches yourperson may be classified obese when he or she is height. A BMI of 25 to 29.9 indicates a person isnot. The BMI is less likely to misidentify a person’s overweight. A person with a BMI of 30 or higherappropriate weight-for-height range. is considered obese. Please review your findings with your health care provider if your BMI is outside of the normal range.Body Mass IndexThe BMI is a tool used to assess overweight and Body Fat Distributionobesity and monitor changes in body weight. Like Health care professionals are concerned not onlythe weight-for-height tables, BMI has its limitations with how much fat a person has, but also wherebecause it does not measure body fat or muscle directly. the fat is located on the body. Women typicallyIt is calculated by dividing a person’s weight in pounds collect fat in their hips and buttocks, givingby height in inches squared and multiplied by 703. them a “pear” shape. Men usually build up fat 2
around their bellies, giving them more of an Environment includes lifestyle behaviors such as“apple” shape. Of course, some men are pear- what a person eats and his or her level of physicalshaped and some women become apple-shaped, activity. Too often Americans eat out, consumeespecially after menopause. large meals and high-fat foods, and put taste andExcess abdominal fat is an important, convenience ahead of nutrition. Also, mostindependent risk factor for disease. Research has people in the United States do not get enoughshown that waist circumference is directly physical activity.associated with abdominal fat and can be usedin the assessment of the risks associated with Environment also includes the world around us—obesity or overweight. If you carry fat mainly our access to places to walk and healthy foods, foraround your waist, you are more likely to example. Today, more people drive long distances todevelop obesity-related health problems. work instead of walking, live in neighborhoodsWomen with a waist measurement of more without sidewalks, tend to eat out or get “take out”than 35 inches and men with a waist instead of cooking, or have vending machines withmeasurement of more than 40 inches may high-calorie, high-fat snacks at their workplace. Ourhave more health risks than people with environment often does not support healthy habits.lower waist measurements because of theirbody fat distribution. In addition, social factors including poverty and a lower level of education have been linked to obesity. One reason for this may be that high-What causes obesity? calorie processed foods cost less and are easier toObesity occurs when a person consumes more find and prepare than healthier foods, such as freshcalories from food than he or she burns. Our vegetables and fruits. Other reasons may includebodies need calories to sustain life and be inadequate access to safe recreation places or thephysically active, but to maintain weight we cost of gym memberships, limiting opportunitiesneed to balance the energy we eat with the for physical activity. However, the link betweenenergy we use. When a person eats more low socio-economic status and obesity has notcalories than he or she burns, the energy been conclusively established, and recent researchbalance is tipped toward weight gain and shows that obesity is also increasing among high-obesity. This imbalance between calories-in and income groups.calories-out may differ from one person toanother. Genetic, environmental, and other Although you cannot change your geneticfactors may all play a part. makeup, you can work on changing your eating habits, levels of physical activity, and other environmental factors. Try these ideas:Genetic Factors ■ Learn to choose sensible portions of nutritiousObesity tends to run in families, suggesting a meals that are lower in fat.genetic cause. However, families also share diet and ■ Learn to recognize and control environmentallifestyle habits that may contribute to obesity. cues (like inviting smells or a package of cookiesSeparating genetic from other influences on obesity on the counter) that make you want to eat whenis often difficult. Even so, science does show a link you are not hungry.between obesity and heredity. ■ Engage in at least 30 minutes of moderate- intensity physical activity (like brisk walking) onEnvironmental and Social Factors most, preferably all, days of the week.Environment strongly influences obesity. Consider ■ Take a walk instead of watching television.that most people in the United States alive today ■ Eat meals and snacks at a table, not in front ofwere also alive in 1980, when obesity rates were the TV.lower. Since this time, our genetic make-up has not ■ Keep records of your food intake and physicalchanged, but our environment has. activity. 3
Other Causes of Obesity What are the consequences of obesity?Some illnesses may lead to or are associated Health Riskswith weight gain or obesity. These include: Obesity is more than a cosmetic problem. Many■ Hypothyroidism, a condition in which the serious medical conditions have been linked to thyroid gland fails to produce enough thyroid obesity, including type 2 diabetes, heart disease, hormone. It often results in lowered high blood pressure, and stroke. Obesity is also metabolic rate and loss of vigor. linked to higher rates of certain types of cancer.■ Cushing’s syndrome, a hormonal disorder Men who are obese are more likely than nonobese caused by prolonged exposure of the body’s men to develop cancer of the colon, rectum, or tissues to high levels of the hormone cortisol. prostate. Women who are obese are more likely Symptoms vary, but most people have upper than nonobese women to develop cancer of the body obesity, rounded face, increased fat gallbladder, uterus, cervix, or ovaries. Esophageal around the neck, and thinning arms and legs. cancer has also been associated with obesity.■ Polycystic ovary syndrome, a condition Other diseases and health problems linked to characterized by high levels of androgens obesity include: (male hormone), irregular or missed ■ Gallbladder disease and gallstones. menstrual cycles, and in some cases, multiple small cysts in the ovaries. Cysts are fluid- ■ Fatty liver disease (also called nonalcoholic filled sacs. steatohepatitis or NASH). ■ Gastroesophageal reflux, or what is sometimes called GERD. This problem occurs when theA doctor can tell whether there are underlying lower esophageal sphincter does not closemedical conditions that are causing weight gain properly and stomach contents leak back—oror making weight loss difficult. reflux—into the esophagus. ■ Osteoarthritis, a disease in which the jointsLack of sleep may also contribute to obesity.Recent studies suggest that people with sleep deteriorate. This is possibly the result of excessproblems may gain weight over time. On the weight on the joints.other hand, obesity may contribute to sleep ■ Gout, another disease affecting the joints.problems due to medical conditions such as sleep ■ Pulmonary (breathing) problems, includingapnea, where a person briefly stops breathing at sleep apnea, which causes a person to stopmultiple times during the night. (Visit breathing for a short time during sleep.www.win.niddk.nih.gov/publications/health_risks.htm ■ Reproductive problems in women, including#sleep for more information on the relationship menstrual irregularities and infertility.between sleep apnea and obesity.) You may wish totalk with your health care provider if you have Health care professionals generally agree that thedifficulty sleeping. more obese a person is, the more likely he or she is to develop health problems.Certain drugs such as steroids, someantidepressants, and some medications for Psychological and Social Effectspsychiatric conditions or seizure disorders may Emotional suffering may be one of the most painfulcause weight gain. These drugs may slow the rate parts of obesity. American society emphasizesat which the body burns calories, stimulate physical appearance and often equates attractivenessappetite, or cause the body to hold on to extra with slimness, especially for women. Such messageswater. Be sure your doctor knows all the may make overweight people feel unattractive.medications you are taking (including over-the-counter medications and dietary supplements). Many people think that individuals with obesity areHe or she may recommend a different medication gluttonous, lazy, or both. This is not true. As athat has less effect on weight gain. result, people who are obese often face prejudice or 4
discrimination in the job market, at school, and in How is obesity treated?social situations. Feelings of rejection, shame, ordepression may occur. The method of treatment depends on your level of obesity, overall health condition, and readiness to lose weight. Treatment may include a combination ofWho should lose weight? diet, exercise, behavior modification, and sometimes weight-loss drugs. In some cases of extreme obesity,Health care professionals generally agree that people bariatric surgery may be recommended. (Visitwho have a BMI of 30 or greater can improve their www.win.niddk.nih.gov/publications/gastric.htm forhealth through weight loss. This is especially true for more information on bariatric surgery.)people with a BMI of 40 or greater, who are Remember, weight control is a life-long effort, andconsidered extremely obese. having realistic expectations about weight loss is anPreventing additional weight gain is recommended if important consideration. Eating a healthful diet andyou have a BMI between 25 and 29.9, unless you getting at least 30 minutes of moderate-intensityhave other risk factors for obesity-related diseases. physical activity on most, preferably all, days of theObesity experts recommend you try to lose weight if week have important health benefits. Sixty minutesyou have two or more of the following: of physical activity a day may be required to prevent gradual weight gain in adulthood. Previously■ Family history of certain chronic diseases. If overweight and obese individuals are encouraged to you have close relatives who have had heart disease get 60 to 90 minutes of exercise a day to sustain or diabetes, you are more likely to develop these weight loss. problems if you are obese.■ Preexisting medical conditions. High blood pressure, high LDL cholesterol levels, low HDL Although most adults do not need to see their cholesterol levels, high triglycerides, and high healthcare professional before starting a moderate- blood glucose are all warning signs of some intensity physical activity program, men older than obesity-associated diseases. 40 years and women older than 50 years who plan a vigorous program or who have either chronic■ Large waist circumference. Men who have waist disease or risk factors for chronic illnesses should circumferences greater than 40 inches, and women speak with their health care provider before who have waist circumferences greater than 35 starting a physical activity program. inches, are at higher risk of diabetes, dyslipidemia (abnormal amounts of fat in the blood), high For more information on health risks, treatment blood pressure, and heart disease. options, and binge eating, refer to these Weight- control Information Network (WIN) publications:Fortunately, a weight loss of 5 to 10 percent of yourinitial body weight can do much to improve health Active at Any Size. Available from WIN and onlineby lowering blood pressure and other risk factors for at www.win.niddk.nih.gov/publications/active.htm.obesity-related diseases. In addition, research shows National Institutes of Health (NIH) Publicationthat a 5- to 7-percent weight loss brought about bymoderate diet and exercise can delay or possibly No. 04-4352. April 2004.prevent type 2 diabetes in people at high risk for thedisease. In a recent study, participants who were Do You Know the Health Risks of Being Overweight?overweight and had pre-diabetes—a condition in Available from WIN and online atwhich a person’s blood glucose level is higher than www.win.niddk.nih.gov/publications/health_risks.htm.normal, but not high enough to be classified as NIH Publication No. 04-4098. November 2004.diabetes—were able to delay or prevent the onset oftype 2 diabetes by adopting a low-fat, low-calorie Healthy Eating and Physical Activity Across Yourdiet and exercising for 30 minutes a day, 5 days a Lifespan: Better Health and You (Tips for Adults).week. For more information about pre-diabetes Available in English and Spanish. Available fromand diabetes, visit www.diabetes.niddk.nih.gov. WIN and online at 5
www.win.niddk.nih.gov/publications/better_health.htm. NIH PublicationNo. 04-4992. June 2004. Weight-controlJust Enough for You: About Food Portions. Available from WIN and Informationonline at www.win.niddk.nih.gov/publications/just_enough.htm. NIH NetworkPublication No. 03-5287. January 2003.Weight Loss for Life. Available from WIN and online at 1 WIN WAYwww.win.niddk.nih.gov/publications/for_life.htm. NIH Publication No. Bethesda, MD 20892-366504-3700. May 2004. Phone: (202) 828-1025For more information on NASH, visit Toll-free number:www.digestive.niddk.nih.gov/ddiseases/pubs/nash/index.htm. 1-877-946-4627 FAX: (202) 828-1028Additional Reading Email: WIN@info.niddk.nih.govNational Institute of Diabetes and Digestive and Kidney Diseases. Internet:Strategic Plan for NIH Obesity Research. U.S. Department of Health and www.win.niddk.nih.govHuman Services (DHHS); NIH. NIH Publication No. 04-5493. 2004. The Weight-control Information NetworkNational Heart, Lung, and Blood Institute. Clinical Guidelines on the (WIN) is a national service of the NationalIdentification, Evaluation, and Treatment of Overweight and Obesity in Institute of Diabetes and Digestive andAdults. DHHS; NIH. NIH Publication No. 98-4083. 1998. Kidney Diseases (NIDDK) of the National Institutes of Health, which is the FederalNational Task Force on Prevention and Treatment of Obesity. Government’s lead agency responsible forOverweight, obesity, and health risk. Archives of Internal Medicine. biomedical research on nutrition and obesity. Authorized by Congress (Public160(7):898-904. 2000. Law 103-43), WIN provides the general public, health professionals, the media, andPartnership for Healthy Weight Management. Weight Loss: Finding a Congress with up-to-date, science-basedWeight Loss Program that Works for You. health information on weight control,Website: www.consumer.gov/weightloss/brochures.htm. 2000. obesity, physical activity, and related nutritional issues.U.S. Department of Agriculture and DHHS. Finding Your Way to aHealthier You: Based on the “Dietary Guidelines for Americans.” Phone: 1- Publications produced by WIN are carefully888-878-3256. Website: www.healthierus.gov/dietaryguidelines. 2005. reviewed by both NIDDK scientists and outside experts. This fact sheet was also reviewed by Steven N. Blair, P.E.D., President and Chief Executive Officer, Cooper Institute. A review was also conducted by Domenica M. Rubino, M.D., Assistant Medical Director, George Washington University Weight Management Program. U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES National Institutes of Health NIH Publication No. 01-3680 October 2001 Updated March 2006