Obesity—now an epidemic in the U.S.—is characterized by excess body weight. Being obese significantly increases one's risk of death from hypertension, stroke, heart disease, and other conditions.


Obesity is a condition of having excess body weight. Adults with a body mass index (BMI, calculated as weight in kilograms divided by height in meters squared) greater than 25 kg/m2 but less than 30 kg/m2 are considered overweight. Adults with a BMI greater than 30 kg/m2 are considered obese.When an adult is more than 100 pounds overweight or has a BMI greater than 40 kg/m2 is considered morbidly obese.

In the U.S., 97 million adults are overweight or obese. Being overweight significantly increases the risk of death from hypertension, dyslipidemia, type 2 diabetes, stroke, osteoarthritis, coronary heart disease, gallbladder disease, sleep apnea and respiratory problems, and endometrial, breast, prostate and colon cancers. Obesity results in an approximate cost of $117 billion in the U.S.

Obesity has reached epic proportions. Rates of obesity have gone up from 12 to 20 percent of the population since 1991. This epidemic is not limited to adults: The percentage of young people who are overweight has more than doubled in the past 20 years. Sixteen percent of children and adolescents between 6 and 19 years old are considered overweight.

Your weight is the result of many factors. These factors include environment, family history and genetics, metabolism (the way your body changes food and oxygen into energy), behavior or habits, and more. You can't change some factors, such as family history. However, you can change other factors, such as your lifestyle habits.


• Consumption of more food than the body can use • Excess alcohol intake • Sedentary lifestyle

Assessing Your Risk Three key measures are used in assessing overweight: • Body mass index (BMI) • Waist circumference • Risk factors for diseases and conditions associated with obesity

The BMI is a measure of your weight in relation to your height, and your waist circumference measures your abdominal fat. Combining these with information about your additional risk factors will give you an idea of your risk for developing obesity-associated diseases.

What is your risk?

Body Mass Index (BMI) BMI is a reliable indicator of total body fat, which is linked to the risk of disease and death. However, while the score is valid, it may overestimate body fat in those with a muscular build, and it may underestimate body fat in older persons or others without much muscle mass.

Waist circumference

Your waist circumference (which you can find by placing a measuring tape snugly around your waist) is a good indicator of your abdominal fat. This is another predictor of developing risk for heart disease and other illnesses. This risk increases with a waist measurement of over 40 inches in men and over 35 inches in women.

Risk of obesity-associated diseases The combination of your BMI and your waist circumference informs you of an increased risk for developing obesity-associated diseases or conditions.

Other risk factors

Besides being overweight or obese, other risk factors are important to consider: • High blood pressure (hypertension) • High LDL-cholesterol ("bad" cholesterol) • Low HDL-cholesterol ("good" cholesterol) • High triglycerides • High blood glucose (sugar) • Family history of premature heart disease • Physical inactivity or a sedentary lifestyle • Cigarette smoking

Assessment For obese or overweight people who have two or more risk factors, federal guidelines recommend weight loss. Even a small weight loss (such as 10 percent of your current weight) lowers your chance of developing diseases associated with obesity. Patients who are overweight but have less than 2 risk factors and do not have a high waist measurement may just need to prevent further weight gain rather than lose weight. Ask your doctor to evaluate your BMI, waist measurement and others risk factors for heart disease. He can let you know your level of risk and whether you should lose weight.


An Inactive Lifestyle

Many Americans aren't very physically active. One reason for this is that many people spend hours in front of TVs and computers doing work, schoolwork, and leisure activities. In fact, more than 2 hours a day of regular TV viewing time has been linked to overweight and obesity.

Other reasons for not being active include: relying on cars instead of walking, fewer physical demands at work or at home because of modern technology and conveniences, and lack of physical education classes in schools for children.

People who are inactive are more likely to gain weight because they don't burn up the calories that they take in from food and drinks. An inactive lifestyle also raises your risk of coronary heart disease, high blood pressure, diabetes, colon cancer, and other health problems.


Our environment doesn't support healthy lifestyle habits; in fact, it encourages obesity. Some reasons include: • Lack of neighborhood sidewalks and safe places for recreation. Not having area parks, trails, sidewalks, and affordable gyms makes it hard for people to be physically active. • Work schedules. People often say that they don't have time to be physically active because of long work hours and time spent commuting. • Oversized food portions. Americans are surrounded by huge food portions in restaurants, fast food places, gas stations, movie theaters, supermarkets, and even home. Some of these meals and snacks can feed two or more people. Eating large portions means too much energy IN. Over time, this will cause weight gain if it isn't balanced with physical activity. • Lack of access to healthy foods. Some people don't live in neighborhoods that have supermarkets that sell healthy foods, such as fresh fruits and vegetables. Or, for some people, these healthy foods are too costly. • Food advertising. Americans are surrounded by ads from food companies. Often children are the targets of advertising for high-calorie, high-fat snacks and sugary drinks. The goal of these ads is to sway people to buy these high-calorie foods, and often they do.

Genes and Family History

Studies of identical twins who have been raised apart show that genes have a strong influence on a person's weight. Overweight and obesity tend to run in families. Your chances of being overweight are greater if one or both of your parents are overweight or obese.

Your genes also may affect the amount of fat you store in your body and where on your body you carry the extra fat. Because families also share food and physical activity habits, a link exists between genes and the environment.

Children adopt the habits of their parents. A child who has overweight parents who eat high-calorie foods and are inactive will likely become overweight too. However, if the family adopts healthy food and physical activity habits, the child's chance of being overweight or obese is reduced.

Health Conditions

Some hormone problems may cause overweight and obesity, such as underactive thyroid (hypothyroidism), Cushing's syndrome, and polycystic ovarian syndrome (PCOS).

Underactive thyroid is a condition in which the thyroid gland doesn't make enough thyroid hormone. Lack of thyroid hormone will slow down your metabolism and cause weight gain. You'll also feel tired and weak.

Cushing's syndrome is a condition in which the body's adrenal glands make too much of the hormone cortisol. Cushing's syndrome also can develop if a person takes high doses of certain medicines, such as prednisone, for long periods.

People who have Cushing's syndrome gain weight, have upper-body obesity, a rounded face, fat around the neck, and thin arms and legs.

PCOS is a condition that affects about 5-10 percent of women of childbearing age. Women who have PCOS often are obese, have excess hair growth, and have reproductive problems and other health issues due to high levels of hormones called androgens.


Certain medicines may cause you to gain weight. These medicines include some corticosteroids, antidepressants, and seizure medicines.

These medicines can slow the rate at which your body burns calories, increase your appetite, or cause your body to hold on to extra water. All of these factors can lead to weight gain.

Emotional Factors

Some people eat more than usual when they're bored, angry, or stressed. Over time, overeating will lead to weight gain and may cause overweight or obesity.


Some people gain weight when they stop smoking. One reason is that food often tastes and smells better after quitting smoking.

Another reason is because nicotine raises the rate at which your body burns calories, so you burn fewer calories when you stop smoking. However, smoking is a serious health risk, and quitting is more important than possible weight gain.


As you get older, you tend to lose muscle, especially if you're less active. Muscle loss can slow down the rate at which your body burns calories. If you don't reduce your calorie intake as you get older, you may gain weight. Midlife weight gain in women is mainly due to aging and lifestyle, but menopause also plays a role. Many women gain around 5 pounds during menopause and have more fat around the waist than they did before.


During pregnancy, women gain weight so that their babies get proper nourishment and develop normally. After giving birth, some women find it hard to lose the weight. This may lead to overweight or obesity, especially after a few pregnancies. Lack of Sleep

Studies find that the less people sleep, the more likely they are to be overweight or obese. People who report sleeping 5 hours a night, for example, are much more likely to become obese compared with people who sleep 7-8 hours a night.

People who sleep fewer hours also seem to prefer eating foods that are higher in calories and carbohydrates, which can lead to overeating, weight gain, and obesity over time.

Hormones that are released during sleep control appetite and the body's use of energy. For example, insulin controls the rise and fall of blood sugar levels during sleep. People who don't get enough sleep have insulin and blood sugar levels that are similar to those in people who are likely to have diabetes.

Also, people who don't get enough sleep regularly seem to have high levels of a hormone called ghrelin (which causes hunger) and low levels of a hormone called leptin (which normally helps curb hunger).


A combination of dieting and exercise (when you stick to it) appears to work better than either one alone. Sticking to a weight reduction program is difficult and requires a lot of support from family and friends.

When dieting, your main goal should be to learn new, healthy ways of eating and make them a part of your everyday routine. Work with your doctor and nutritionist to set realistic, safe daily calorie counts that assure both weight loss and good nutrition. Remember that if you drop pounds slowly and steadily, you are more likely to keep them off. Your nutritionist can teach you about healthy food choices, appropriate portion sizes, and new ways to prepare food. Even modest weight loss can improve your health. Most people can lose weight by eating a healthier diet, exercising more, and adopting new behaviors such as keeping a food diary, avoiding food triggers, and thinking positively. The decision to keep fit requires a lifelong commitment of time and effort. Patience is essential.

Several simple behavioral changes can have an impact on your weight loss success:

• Set realistic goals for weight reduction. One should engage in aerobic exercise for at least 30 minutes a day, 3 times a week, and try to increase physical activity in general. • Eat only at the table. No snacking in front of the TV, in bed, while driving, or while standing in front of the open refrigerator. • Learn about appropriate portion sizes. • Choose low-calorie snacks, such as raw vegetables. • Consider learning meditation or yoga as a way of managing stress, rather than snacking. • Find ways to socialize and enjoy your friends and family that don't involve a meal or dessert. • Consider keeping a diet and exercise journal. This may help you identify overeating triggers in your life. • Find a support group or consider psychotherapy to help support you in the difficult but worthy goal of weight loss.

Key recommendations from the expert panel on the Identification, Evaluation and Treatment of Overweight and Obesity in Adults:

The initial goal of weight-loss therapy should be to reduce body weight by about 10 percent from baseline. For the first six months, weight loss should be approximately one to two pounds per week. If necessary, the patient can continue to lose more weight.

Reducing dietary fat alone without reducing calories is not enough to cause weight loss. However, reducing dietary fat along with reducing dietary carbohydrates can help reduce calories.

Drug therapy can also be used. However, drug safety and efficacy beyond one year of total treatment have not been established.

Selecting a weight loss program

Some people lose weight on their own; others like the support of a structured program. If you decide to join any kind of weight-control program, here are some questions to ask before you join.

• Does the program provide counseling to help you change your eating and personal habits? • Will this program teach you how to permanently change habits and lifestyle factors that have contributed to weight gain? • Is the staff made up of a variety of qualified counselors and health professionals such as nutritionists, registered dietitians, doctors, nurses, psychologists and exercise physiologists?

You need an evaluation by a physician if you have any health problems, are currently taking or plan on taking any medicine or plan to lose more than 15 to 20 pounds. If your weight-control plan uses a very low-calorie diet, you need an exam and follow-up visits by a doctor.

• Is training available on how to deal with times when you may feel stressed and slip back to old habits? Is attention paid to keeping the weight off, and how long is this phase?

The program should provide long-term strategies for dealing with weight problems that may come up in the future. These strategies might include things like establishing a support system and establishing a physical activity routine.

• Are food choices flexible and well-suited to the individual? Are weight goals set by the client and the health professional? The program should consider your food likes and dislikes and your lifestyle when your weight-loss goals are planned. • What percentage of people completes the program? • What is the average weight loss among people who finish the program? • What percentage of people has problems or side effects, and what are they? • Are there fees or costs for additional items, such as dietary supplements?

Quick weight-loss methods do not lead to lasting results. Relying on diet aids like drinks, prepackaged foods or pills don't work over the long term. No matter how much weight you wish to lose, modest goals and a slow pace will increase your chances of losing the weight and keeping it off.

Guide to physical activity

Not only is exercise an integral part of a weight loss and weight maintenance plan, it also reduces the risk of cardiovascular disease and diabetes, beyond that produced by weight reduction alone.

Your exercise can be done all at one time, or intermittently over the day. Initial activities may be walking or swimming at a slow pace. Your regimen can be adapted to other forms of physical activity, but walking is a particularly smart choice because of its safety and accessibility. Increasing activity by undertaking frequent, less strenuous exercises, such as walking up and down the stairs instead of the using the elevator. You may eventually be able to engage in more strenuous activities such as tennis or any form of group sport.

Guide to behavior change

Over the past few years it has become clear that many people suffer from health issues due to weight. Some people who need to lose weight for their health don't recognize it, while others who don't need to lose weight want to get thinner for cosmetic reasons.

Weight can affect a person's self-esteem. Excess weight is clearly visible and may attract ridicule. The amount of weight loss needed to improve your health may be much less than your total weight-loss goal. Your health can be greatly improved by a loss of 5-10 percent of your starting weight. That doesn't mean you have to stop there, but it does mean that an initial goal of losing 5-10 percent of your starting weight is both realistic and valuable.

Balance your (food) checkbook

Healthy food shopping

National Heart, Lung, and Blood Institute Obesity Guidelines

So, shop for quick low fat food items and fill your kitchen cupboards with a supply of basics like the following:

• Fat free or low-fat milk, yogurt, cheese, and cottage cheese • Light or diet margarine • Eggs/Egg substitutes • Sandwich breads, bagels, pita bread, English muffins • Soft corn tortillas, low fat flour tortillas • Low fat, low sodium crackers • Plain cereal, dry or cooked • Rice, pasta • White meat chicken or turkey (remove skin) • Fish and shellfish (not battered) • Beef: round, sirloin, chuck arm, loin and extra lean ground beef • Pork: leg, shoulder, tenderloin • Dry beans and peas • Fresh, frozen, canned fruits in light syrup or juice • Fresh, frozen, or no salt added canned vegetables • Low fat or nonfat salad dressings • Mustard and catsup • Jam, jelly, or honey • Herbs and spices • Salsa


Weight-loss surgery may be an option if you are very obese and have not been able to lose weight through diet and exercise. However, these surgeries are not a "quick fix" for obesity. You must still be committed to diet and exercise after the surgery. Talk to your doctor to learn if this is a good option for you.

The two most common weight-loss surgeries are:

• Laparoscopic gastric banding -- the surgeon places a band around the upper part of your stomach, creating a small pouch to hold food. The band limits the amount of food you can eat by making you feel full after eating small amounts of food. • Gastric bypass surgery -- helps you lose weight by changing how your stomach and small intestine handle the food you eat. After the surgery, you will not be able to eat as much as before, and your body will not absorb all the calories and other nutrients from the food you eat.


  • Center for Disease Control
  • National Heart, Lung and Blood Institute
  • National Institutes of Health - National Library of Medicine
  • U.S. Department of Health and Human Services
  • National Institute of Diabetes & Digestive & Kidney Diseases.
Last reviewed 02/17/2015