Reviewed on 11/17/2022

Things to Know About Obesity

Serving a variety of vegetables rather than just one vegetable with a meal will help you maintain a healthy weight.
Serving a variety of vegetables rather than just one vegetable with a meal will help you maintain a healthy weight.

The foods we eat every day contribute to our well-being. Foods provide us with the nutrients we need for healthy bodies and the calories we need for energy. If we take in more calories than we burn, the extra food turns into fat and is stored in our bodies. If we overeat regularly, we gain weight, and if we continue to gain weight, we may become obese.

Obesity results from the accumulation of excess fat in the body. Obesity is considered a chronic (long-term) disease, like high blood pressure or diabetes. It has many serious long-term consequences for your health, and it is a leading cause of preventable deaths in the United States (with tobacco use and high blood pressure). Obesity is defined as having a body mass index (BMI) greater than 30. The BMI is a measure of your weight relative to your height.

Obesity is an epidemic in the United States and in other developed countries. More than two-thirds of Americans are overweight, including at least one in five children. Nearly one-third are obese. Obesity is on the rise in our society because food is abundant and most of us are employed in positions that require little to no physical activity. On the bright side, recent data suggest that childhood obesity, while still high, may no longer be on the rise.

What Are Causes of Obesity?

Weight gain occurs when you eat more calories than your body uses up. If the food you eat provides more calories than your body needs, the excess is converted to fat. Initially, fat cells increase in size. When they can no longer expand, they increase in number. If you lose weight, the size of the fat cells decreases, but the number of cells does not.

  • Obesity, however, has many causes. The reasons for the imbalance between calorie intake and consumption vary by individual. Your age, gender, genes, psychological makeup, socioeconomic, and environmental factors all may contribute.
    • Genes: Your genes may play a role in the efficiency of metabolism and storage and distribution of body fat.
    • Family lifestyle: Obesity tends to run in families. This is caused both by genes and by shared diet and lifestyle habits. If one of your parents is obese, you have a higher risk of being obese.
    • Emotions: Some people overeat because of depression, hopelessness, anger, boredom, and many other reasons that have nothing to do with hunger. This doesn't mean that overweight and obese people have more emotional problems than other people. It just means that their feelings influence their eating habits, causing them to overeat.
    • Environmental factors: The most important environmental factor is lifestyle. Your eating habits and activity level are partly learned from the people around you. Overeating and sedentary habits (inactivity) are the most important risk factors for obesity.
    • Socioeconomic factors: Do you live in a neighborhood where it is safe to exercise outdoors? Are there supermarkets with fresh foods in your neighborhood?
    • Sex: Men have more muscle than women, on average. Because muscle burns more calories than other types of tissue, men use more calories than women, even at rest. Thus, women are more likely than men to gain weight with the same calorie intake.
    • Age: People tend to lose muscle and gain fat as they age. Their metabolism also slows somewhat. Both of these lower their calorie requirements.
    • Pregnancy: Women tend to weigh an average of 4-6 pounds more after a pregnancy than they did before the pregnancy. This can compound with each pregnancy.
  • Certain medical conditions and medications can cause or promote obesity, although these are much less common causes of obesity than overeating and inactivity. Some examples of these are as follows:
  • Obesity can be associated with other eating disorders, such as binge eating or bulimia.
  • The distribution of your body fat also plays a role in determining your risk of obesity-related health problems. There are at least two different kinds of body fat. Studies conducted in Scandinavia have shown that excess body fat distributed around the waist (apple-shaped figure, intra-abdominal fat) carries more risk than fat distributed on the hips and thighs (pear-shaped figure, fat under the skin).

What Symptoms and Signs Are Associated With Obesity?

For most people, obesity becomes a lifelong struggle. Obesity is caused by multiple factors, and although the principle of decreased caloric intake and increase in exercise is a relatively simple concept, there are many underlying reasons that lead to obesity in an individual. Treatment, therefore, has to take all of this into consideration. The need to manage obesity is clear as obesity increases your risk of many other diseases and health problems, including the following:

Depression may be one of the most common effects of obesity. Many obese people suffer emotional distress. Because of the emphasis on physical appearance in our culture, which equates slimness with beauty, obese people may feel unattractive. They also are subjected to prejudice, ridicule, and discrimination, which may make them feel ashamed or rejected.

Obesity is also a major risk factor for the development of diabetes mellitus. The good news is that this may be preventable. In clinical studies, patients who were at a high risk of developing diabetes decreased their risk by almost 60% with less than 10% weight loss in three years.

How Do Health Care Professionals Diagnose Obesity?

Weight-to-Height Tables

These tables give general ranges of healthy weights and overweight for adult height. The tables do not take into account individual conditions. For one thing, they do not distinguish fat from muscle, water, or bone. They are much less helpful than body mass index in identifying the risk of health problems related to weight.

Body Fat Percentage

Many health professionals agree that percentage of body weight that is fat is a good marker of obesity. Men with more than 25% fat and women with more than 32% fat are considered obese.

Body fat percentage is difficult to measure accurately, however. Special equipment is needed that is not found at most medical offices. The methods used at health clubs and weight-loss programs may not be accurate if not done properly. Inexpensive scales for home use that estimate body fat are now widely available. They may not be entirely accurate but are generally consistent, so they may be used over time to track one's progress.

Waist measurement is also an important factor. People with apple or pot belly shapes, who tend to put on weight around their waist, have a higher risk of obesity-related health problems. This includes women with a waist measurement of greater than 35 inches and men with a waist measurement of greater than 40 inches.

Body Mass Index

A measure called the body mass index (BMI) is used to assess your weight relative to your height. It is defined as weight in kilograms divided by height in meters squared (kg/m2). It can also be calculated for weight in pounds and height in inches.

Body mass index is closely related to body fat percentage but is much easier to measure. Therefore, it is used by many primary care providers to identify obesity. The greater your BMI, the higher your risk of developing health problems related to excess weight.

To calculate your body mass index, follow these steps:

  • Multiply your weight in pounds by 705.
  • Then divide by your height in inches.
  • Divide this by your height in inches again.

What does BMI tell you?

  • Normal weight = 18.5-24.9
  • Overweight = 25.0-29.9
  • Obese = 30 or greater
  • Morbidly obese = 40 or greater

To calculate your body mass index on the Internet, fill in your height and weight at the web site of the government's National Heart, Lung, and Blood Institute's Obesity Education Initiative.

What Is the Treatment for Obesity?

  • For most people who are overweight or obese, the safest and most effective way to lose weight is to eat less and exercise more. If you eat less and exercise more, you will lose weight. It is as simple as that.
  • Any weight-loss program, including medical and surgical approaches, will also include decreasing caloric intake and exercise.
  • There are no magic pills.
  • Diets that sound too good to be true are just that.

When Should Someone Seek Medical Care for Obesity?

If you are obese, you should have a primary care physician who follows you closely and monitors you for the known complications of obesity such as diabetes, hypertension, and heart disease. The following are additional indications to see a health care provider:

  • If you are overweight or obese and don't know how to lose weight
  • If you are concerned about the effects of a weight-loss diet or increased physical activity on your other medical problems
  • If you are unsuccessful at losing weight on your own
  • If you are concerned about the safety of your weight-loss method

Are There Home Remedies for Obesity?

  • By decreasing your daily calorie intake by 500 calories or expending an extra 500 calories during exercise each day, you will lose about 1 pound per week.
  • Decreasing your calorie intake by 10 calories a day will equal 1 pound of weight loss after one year.
  • Any good diet plan will include exercise. It helps to increase metabolism and is one less opportunity to eat during the day.
    • You should exercise for at least 30 minutes, five times a week.
    • Regular exercise also helps your heart and lungs and lowers triglyceride levels that can cause heart disease. It also increases HDL ("good cholesterol") levels.
    • Even simple measures such as taking the stairs instead of the elevator and short walks eventually add up to a lot of calories burned.
    • Commercial fitness programs such as Boot Camp can help you start or improve upon a fitness program.
  • Group support programs such as Weight Watchers or Take Off Pounds Sensibly, known as TOPS, provide peer support and promote healthy habits.
  • For those who don't have the time to make it to support groups, there are now many free or low-cost apps available for the iPhone, iPad, or Android, which help determine and track calories, nutrition, and calorie expenditure.
    • Try LoseIt!,
    • Weight Watchers Mobile,
    • Restaurant Nutrition,
    • 40:30:30,
    • Diet Point,
    • Noom Weight Loss Coach,
    • Fitbit,
    • Fooducate,
    • Diet Assistance,
    • Calorie Counter PRO MyNet Diary,
    • Amwell,
    • MyFitnessPal, or
    • 7-Minute Workout.

For a more complete discussion of lifestyle changes that are helpful in losing weight, see Weight Loss and Control.

Of special interest to women who have gained weight after having a baby is the fact that breastfeeding helps you shed some extra pounds. Besides the positive effects for the baby, breastfeeding burns approximately 500 extra calories each day.

What Is the Medical Treatment for Obesity?

Medical treatment of obesity focuses on lifestyle changes such as eating less and increasing activity levels. There are medications that can promote weight loss, although they work only in conjunction with eating less and exercising more.

Most medications that promote weight loss work by suppressing the appetite. Some medications used in the past have been shown to be unsafe and are no longer available. The newer appetite-suppressing medications are thought to be safe, but they do have side effects and may interact with certain other drugs. They are used only under the supervision of a health care professional.

For more information about weight-loss medications, go to the article Medication in the Treatment of Obesity.

Some weight-loss products are known to be dangerous. The safety of others is in question. This includes certain prescription and over-the-counter drugs and herbal supplements. Avoid them.

  • "Phen-fen" and Redux: These prescription drugs have been removed from the market in the United States and many other countries. They are linked to heart-valve problems and pulmonary hypertension. Pulmonary hypertension affects the blood vessels in the lungs and is often fatal.
  • Ephedra: This natural substance is essentially an herbal phen-fen. It is the active ingredient in MaHuang and is used as a stimulant and appetite suppressant. Ephedra resembles amphetamines -- the popular "diet drugs" that were banned in the 1970s -- in that it is highly addictive. Ephedra is often combined with caffeine and aspirin ("the Stack"), which increases the thermogenic (fat-burning) effect of ephedra. Ephedra increases the risk of high blood pressure, irregular heartbeat, insomnia, seizures, heart attack, stroke, and death. The FDA has recently banned ephedra because it has been linked to more than 100 deaths.
  • Phenylpropanolamine (PPA) is often found in appetite suppressants as well as over-the-counter cough and cold remedies. The FDA has recommended that products containing PPA be removed from the market. Studies have suggested that this product is associated with an increased risk of hemorrhagic (bleeding) stroke in women.
  • Sibutramine is an oral anorexiant that was removed from the U.S. market in 2010 due to the risk of serious adverse cardiovascular events.

Some people have tried combining more than one weight-loss drug or combining a weight-loss drug with other drugs for the purpose of losing weight. The safety and effectiveness of such drug "cocktails" is not known.

What Are Medications for Obesity?

The following medications are available in the United States by prescription. If you have been unsuccessful in losing weight through diet and exercise, ask your doctor about these medications. For more information about these drugs, see Medication in the Treatment of Obesity. These are not a substitute for dietary management. Over the long term, successful long-term weight loss requires changes in overall eating patterns.

  • Orlistat (Xenical 120 mg by prescription or Alli 60 mg available over the counter) is a medication approved by the FDA in 1999. Your doctor may prescribe it if you weigh more than 30% over your healthy body weight or have a BMI greater than 30. Over one year, people who followed a weight-loss diet and took orlistat lost an average of 13.4 pounds, almost 8 pounds more than people who used diet alone to lose weight. It works by reducing the absorption of fat from the intestine. Diarrhea and incontinence of stool may be side effects of this medicine.
  • Lorcaserin (Belviq 10 mg one to two times daily) was approved by the FDA in 2012. It may be considered if your BMI is 30 or greater or if you have a BMI greater than 27 with weight-related conditions. Studies demonstrated that 50% of patients lost an average of 5% of their body weight when combined with diet and exercise (compared to 25% of patients with diet and exercise alone). Lorcaserin works by activating the serotonin 2C receptor in the brain, which helps you feel full after smaller portions. The most common side effects were headache, nausea, and dizziness.
  • Qsymia (a combination of phentermine and topiramate) was approved by the FDA in 2012. It is only approved for those with a BMI greater than 27 with weight-related conditions. When combined with diet and exercise, studies have shown that half of the participants lost 10% of their body weight and four-fifths lost 5% (which equates to 12 pounds in a 227-pound person). Topiramate is associated with a high risk of birth defects such as cleft lip and palate. Phentermine (an appetite suppressant) was one of the ingredients in fen-phen and is associated with an elevation in heart rate. Because of these potentially serious side effects, Qsymia is only available through mail order. Other side effects include tingling, dizziness, alterations in taste, insomnia, dry mouth, and constipation.
  • Contrave, a combination of bupropion (an antidepressant) and naltrexone (used to treat opiate abuse) was approved by the FDA in 2014 to treat adults with a BMI of 30 or more, or a BMI of 27 or more if you have a weight-related illness, such as hypertension, type 2 diabetes, or high cholesterol. Studies have shown that approximately 40% of patients taking Contrave lost 5% or more of their total body weight after one year. This medication can cause elevated blood pressure and seizures. It should not be taken if you are being treated with opiates such as morphine, hydromorphone, oxycodone, or hydrocodone. Side effects can include nausea, vomiting, diarrhea, constipation, dizziness, insomnia, and dry mouth.

Is Bariatric Surgery an Effective Treatment for Obesity?

Surgery to correct obesity (known as bariatric surgery) is a solution for some obese people who cannot lose weight on their own or have severe obesity-related medical problems. Generally, surgery is recommended only for morbidly obese people (body mass index 40 or greater). This means men who are at least 100 pounds overweight and women who are at least 80 pounds overweight.

The two types of bariatric surgery are malabsorptive and restrictive.

  • Malabsorptive procedures decrease intestinal absorption of food by bypassing part of the digestive system. A greater proportion of food than usual passes through without being absorbed.
  • Restrictive procedures decrease the amount of food that a person can take in by decreasing the size of the stomach.

Both surgical strategies entail changes in how food is processed in the body. While they are successful in helping some people lose weight, they also may cause cramps, diarrhea, and other unpleasant effects, as well as iron deficiency anemia. For more information, go to the article Surgery in the Treatment of Obesity.

Liposuction is purely a cosmetic procedure that removes fat cells but has no beneficial effects on health, such as heart disease and diabetes.

Vagal blockade involves surgically implanting a device that stimulates the abdominal vagal nerve, thereby sending signals to the brain that say you are full, which can reduce hunger. Short-term studies have shown modest weight loss (about 18 pounds). No long-term studies have been done yet, and some patients develop pain at the implantation site as well as nausea, vomiting, heartburn, and burping.

What Lifestyle Changes Help Obesity?

Behavior modification is a fancy name for changing your attitude toward food and exercise. These changes promote new habits and attitudes that help you lose weight. Many people find they cannot lose weight or keep it off unless they change these attitudes. Behavior-modification techniques are easy to learn and practice. Most involve increasing your awareness of situations in which you overeat so that you can stop overeating.

What Can People Do to Prevent Obesity?

Reversing obesity and its health risks requires changing the habits of a lifetime. Eating less over the long term means learning to think about your eating habits and patterns.

What makes you overeat? Coffee break at work? Going out with friends? Watching TV? Late-afternoon energy lag? Late-night sweet tooth? Are you the one who finishes the last serving of dinner just so there won't be any leftovers? Do you eat high-calorie fast foods or snacks because you don't have time or energy to cook? Having some insight into your overeating habits helps you to avoid your problem situations and reach your weight goal.

Likewise, increasing your activity level is largely a matter of changing your attitude. You don't have to become a marathon runner. Thirty minutes of aerobic activity five days a week will make a significant difference in your health. Look for ways to increase your activity level doing things you enjoy.

For some strategies that may help you change your habits, go to the article Weight Loss and Control.

Where Can People Find Obesity Support Groups and Counseling?

American Obesity Association: This group itself is not for profit, but it is made up of several types of sponsors, including professional groups such as the American College of Nutrition as well as health-insurance interests, for-profit companies such as drug and biotechnology companies, and weight-loss interests such as Jenny Craig, Inc., and Weight Watchers, Inc. The group's purpose is to change the way obesity is perceived and to end discrimination against obese people, as well as to find more effective strategies for preventing and "curing" obesity. It uses lobbying, advocacy, and education to achieve these goals.

Association for Morbid Obesity Support: This group provides "peer support and resources for morbid obesity and bariatric surgery."

Where Can People Find More Information on Obesity?

American Heart Association

American Society for Bariatric Surgery

Association for Coordination and Research in Obesity and Nutrition: This European group provides information on obesity research in Europe. The website has information in English and French.

Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Nutrition and Physical Activity, Overweight and Obesity

National Institutes of Health, Health Information: Weight Loss and Control

National Obesity Education Initiative, Aim for a Healthy Weight, Information for Patients and the Public

Obesity Law and Advocacy Center: This is a law firm in San Diego, Calif., that specializes in legal issues in obesity.

Obesity Treatment

Criteria for Bariatric Surgery

Weight loss surgery candidates must fulfill all the following criteria:

  • Body mass index (BMI) greater than 40 or a BMI of at least 35 with obesity-related medical problems such as diabetes, heart disease, hypertension, sleep apnea, or high blood lipids
  • Previously attempted nonsurgical weight-loss treatments and failed to achieve long-term weight loss
  • Well-informed and motivated for long-term follow-up to achieve substantial weight loss
  • Acceptable medical risks for surgery
Reviewed on 11/17/2022
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