Overweight and obesity is a serious health problem that affects millions of Americans. These conditions substantially increase the risk of morbidity from hypertension; dyslipidemia; type 2 diabetes; coronary heart disease; stroke; gallbladder disease; osteoarthritis; sleep apnea and respiratory problems; and endometrial, breast, prostate, and colon cancers. Higher body weights also are associated with increases in all-cause mortality.

Adults

According to the National Health and Nutrition Examination Survey (NHANES) data from 2007–08, the overall prevalence of overweight and obesity for adults was 68 percent (approximately 72 percent among men and 64 percent among women).

• Among women, the overall prevalence of obesity was 35.5 percent.
• Among men, the overall prevalence of obesity was 32.2 percent.

Children and Teens

This rate, though, remains alarmingly high. Statistics show about 17 percent of American children ages 2 to 19, or 1 in 6, are obese. Further, the latest data continue to suggest that overweight and obesity are having a greater effect on minorities, including blacks and Hispanics.

Understanding Adult Obesity

Today, 66 percent of adults in the United States are considered overweight or obese. Obesity puts people at increased risk for chronic diseases such as heart disease, type 2 diabetes, high blood pressure, stroke, and some forms of cancer.

The large number of people considered to be obese and the serious health risks that come with it make understanding its causes and treatment crucial. This fact sheet provides basic information about obesity: What is it? How is it measured? What causes it? What are the health risks? What can you do about it?

What is obesity? Obesity specifically refers to an excessive amount of body fat. “Overweight” refers to an excessive amount of body weight that includes muscle, bone, fat, and water. There are few studies in humans that link direct measurements of total body fat to morbidity and mortality. There are also no official standards identified by the National Institutes of Health (NIH) that define obesity based on the amount or percentage of a person’s total body fat.

What causes obesity?

Obesity occurs when a person consumes more calories from food than he or she burns. Our bodies need calories to sustain life and be physically active, but to maintain weight we need to balance the energy we eat with the energy we use. When a person eats more calories than he or she burns, the energy balance is tipped toward weight gain and obesity. This imbalance between calories-in and calories-out may differ from one person to another. Genetic, environmental, and other factors may all play a part.

Genetic Factors

Obesity tends to run in families, suggesting a genetic cause. However, families also share diet and lifestyle habits that may contribute to obesity. Separating genetic from other influences on obesity is often difficult. Even so, science does show a link between obesity and heredity.

Environmental and Social Factors

Environment strongly influences obesity. Consider that most people in the United States alive today were also alive in 1980, when obesity rates were lower. Since this time, our genetic make-up has not changed, but our environment has.

Environment includes lifestyle behaviors such as what a person eats and his or her level of physical activity. Too often Americans eat out, consume large meals and high-fat foods, and put taste and convenience ahead of nutrition. Also, most people in the United States do not get enough physical activity.

Environment also includes the world around us—our access to places to walk and healthy foods, for example. Today, more people drive long distances to work instead of walking, live in neighborhoods without sidewalks, tend to eat out or get “take out” instead of cooking, or have vending machines with high-calorie, high-fat snacks at their workplace. Our environment often does not support healthy habits.

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-calorie processed foods cost less and are easier to find and prepare than healthier foods, such as fresh vegetables and fruits. Other reasons may include inadequate access to safe recreation places or the cost of gym memberships, limiting opportunities for physical activity. However, the link between low socioeconomic status and obesity has not been conclusively established, and recent research shows that obesity is also increasing among high-income groups.

Cultural Factors

An individual’s cultural background may also play a role in his or her weight. For instance, foods specific to certain cultures that are prepared with a lot of fat or salt may hamper one’s weight-loss efforts. Similarly, family gatherings offering large amounts of food may make it difficult to pay attention to proper portion control and serving sizes. Lastly, research has shown that individuals originally from countries other than the United States have difficulty adjusting to the calorie-rich foods offered here. These individuals may not be able to prepare food with the ingredients they would use in their native countries.

Although you cannot change your genetic makeup, you can work on changing your eating habits, levels of physical activity, and other environmental factors. Try these ideas:

• Learn to choose sensible portions of nutritious meals that are lower in fat.
• Learn healthier ways to make your favorite foods.
• Learn to recognize and control environmental cues (like inviting smells or a package of cookies on the counter) that make you want to eat when you are not hungry.
• Have a healthy snack an hour or two before a social gathering to prevent overeating. Mingle and talk between bites to prevent eating too much too quickly.
• Engage in at least 30 minutes of moderate-intensity physical activity (like brisk walking) on most, preferably all, days of the week.
• Take a walk instead of watching television.
• Eat meals and snacks at a table, not in front of the TV.
• Pay attention to why you are eating. Determine if you are eating because you are actually hungry or because you are bored, depressed, or lonely.
• Keep records of your food intake and physical activity.

Other Causes of Obesity

Some illnesses may lead to or are associated with weight gain or obesity. These include:

• Hypothyroidism, a condition in which the thyroid gland fails to produce enough thyroid hormone. It often results in lowered metabolic rate and loss of vigor.
• Cushing’s syndrome, a hormonal disorder caused by prolonged exposure of the body’s tissues to high levels of the hormone cortisol. Symptoms vary, but most people have upper body obesity, rounded face, increased fat around the neck, and thinning arms and legs.
• Polycystic ovary syndrome, a condition characterized by high levels of androgens (male hormone), irregular or missed menstrual cycles, and in some cases, multiple small cysts in the ovaries. Cysts are fluid-filled sacs.

A doctor can tell whether there are underlying medical conditions that are causing weight gain or making weight loss difficult.

Lack of sleep may also contribute to obesity. Recent studies suggest that people with sleep problems may gain weight over time. On the other hand, obesity may contribute to sleep problems due to medical conditions such as sleep apnea, where a person briefly stops breathing at multiple times during the night. (Visit Health Risks for more information on the relationship between sleep apnea and obesity.) You may wish to talk with your health care provider if you have difficulty sleeping.

Certain drugs such as steroids, some antidepressants, and some medications for psychiatric conditions or seizure disorders may cause weight gain. These drugs may slow the rate at which the body burns calories, stimulate appetite, or cause the body to hold on to extra water. Be sure your doctor knows all the medications you are taking (including over-the-counter medications and dietary supplements). He or she may recommend a different medication that has less effect on weight gain.

What are the consequences of obesity?

Health Risks

Obesity is more than a cosmetic problem. Many serious medical conditions have been linked to obesity, including type 2 diabetes, heart disease, high blood pressure, and stroke. Obesity is also linked to higher rates of certain types of cancer. Esophageal cancer has also been associated with obesity.

• Men who are considered obese are more likely than nonobese men to develop cancer of the colon, rectum, or prostate.
• Women who are considered obese are more likely than nonobese women to develop cancer of the gallbladder, uterus, cervix, or ovaries.

Other diseases and health problems linked to obesity include:

• Gallbladder disease and gallstones.
• Fatty liver disease (also called nonalcoholic steatohepatitis or NASH).
• Gastroesophageal reflux, or what is sometimes called GERD. This problem occurs when the lower esophageal sphincter does not close properly and stomach contents leak back—or reflux—into the esophagus.
• Osteoarthritis, a disease in which the joints deteriorate. This is possibly the result of excess weight on the joints.
• Gout, another disease affecting the joints.
• Pulmonary (breathing) problems, including sleep apnea, which causes a person to stop breathing for a short time during sleep.
• Reproductive problems in women, including menstrual irregularities and infertility.

Health care professionals generally agree that the more obese a person is, the more likely he or she is to develop health problems.

Emotional suffering may be one of the most painful parts of obesity. American society emphasizes physical appearance and often equates attractiveness with slimness, especially for women. Such messages may make people considered overweight feel unattractive.

Many people think that individuals who are considered obese are gluttonous, lazy, or both. This is not true. As a result, people who are considered obese often face prejudice or discrimination in the job market, at school, and in social situations. Feelings of rejection, shame, or depression may occur.

Risk Factors for Health Associated With Obesity

Along with being overweight or obese, the following conditions will put you at greater risk for heart disease and other conditions:

• High blood pressure (hypertension)
• High LDL cholesterol (“bad” cholesterol)
• High triglycerides
• Family history of premature heart disease
• Physical inactivity
• Cigarette smoking

For people who are considered obese (BMI greater than or equal to 30) or those who are overweight (BMI of 25 to 29.9) and have two or more risk factors, it is recommended that you lose weight. Even a small weight loss (between 5 and 10 percent of your current weight) will help lower your risk of developing diseases associated with obesity. People who are overweight, do not have a high waist measurement, and have fewer than two risk factors may need to prevent further weight gain rather than lose weight.

Talk to your doctor to see whether you are at an increased risk and whether you should lose weight. Your doctor will evaluate your BMI, waist measurement, and other risk factors for heart disease.

How is obesity treated?

The method of treatment depends on your level of obesity, overall health condition, and readiness to lose weight. Treatment may include a combination of diet, exercise, behavior modification, and sometimes weight-loss drugs. In some cases of extreme obesity, bariatric surgery may be recommended. (Visit NIDDK for more information on bariatric surgery.)

Remember, weight control is a life-long effort, and having realistic expectations about weight loss is an important consideration. Eating healthier foods and getting at least 30 minutes of moderate-intensity physical activity on most, preferably all, days of the week have important health benefits. Sixty minutes of physical activity a day may be required to prevent gradual weight gain in adulthood. Individuals who were previously considered overweight and obese individuals are encouraged to get 60 to 90 minutes of exercise a day to sustain weight loss.

Although most adults do not need to see their health care professional before starting a moderate-intensity physical activity program, men older than 40 years and women older than 50 years who plan a vigorous program, or who have either chronic disease or risk factors for chronic illnesses, should speak with their health care provider before starting a physical activity program.

Stigma of Obesity

What is your reaction to this photo of a man and girl at the beach? Compassion? Fear? Disgust? Many people will look at this picture and make negative assumptions about the man based on his weight. According to a study from the Yale Rudd Center for Food Policy and Obesity, large people are the object of “widespread negative stereotypes that overweight and obese persons are lazy, unmotivated, lacking in self-discipline, less competent, noncompliant, and sloppy” (Puhl and Heuer 2009).

Historically, both in the United States and elsewhere, it was considered acceptable to discriminate against people based on prejudiced opinions. Even after slavery was abolished in 1865, the next 100 years of American history saw institutionalized racism and prejudice against black people. In an example of stereotype interchangeability, the same insults that are flung today at the overweight and obese population (lazy, for instance), have been flung at various racial and ethnic groups in earlier history. Of course, no one gives voice to these kinds of views in public now, except when talking about obese people.Why is it considered acceptable to feel prejudice toward—even to hate—obese people? Puhl and Heuer suggest that these feelings stem from the perception that obesity is preventable through self-control, better diet, and more exercise. Highlighting this contention is the fact that studies have shown that people’s perceptions of obesity are more positive when they think the obesity was caused by non-controllable factors like biology (a thyroid condition, for instance) or genetics.

Even with some understanding of non-controllable factors that might affect obesity, obese people are still subject to stigmatization. Puhl and Heuer’s study is one of many that document discrimination at work, in the media, and even in the medical profession. Obese people are less likely to get into college than thinner people, and they are less likely to succeed at work.

Stigmatization of obese people comes in many forms, from the seemingly benign to the potentially illegal. In movies and television show, overweight people are often portrayed negatively, or as stock characters who are the butt of jokes. One study found that in children’s movies “obesity was equated with negative traits (evil, unattractive, unfriendly, cruel) in 64 percent of the most popular children’s videos. In 72 percent of the videos, characters with thin bodies had desirable traits, such as kindness or happiness” (Hines and Thompson 2007). In movies and television for adults, the negative portrayal is often meant to be funny. “Fat suits”—inflatable suits that make people look obese—are commonly used in a way that perpetuates negative stereotypes. Think about the way you have seen obese people portrayed in movies and on television; now think of any other subordinate group being openly denigrated in such a way. It is difficult to find a parallel example.