Was this helpful?

What is obesity?

Obesity is a common condition in which there is an excessive amount of body fat to a degree that puts a person at risk for serious chronic health problems, such as diabetes or hypertension. Obesity is a major health epidemic that affects all populations, regardless of gender or race, and it is becoming more common in children as well as adults. The Centers for Disease Control and Prevention (CDC) estimates that about 34% of the U.S. adult population is obese and 5.9% is extremely obese (Source: CDC).

Obesity is caused by eating more calories than the body consumes (burns off) for energy over a period of time. Obesity is not necessarily the same thing as being overweight. Overweight is defined as weighing more than what is generally considered normal based on your height. However, being overweight can occasionally be caused by increased muscle size or water retention and does not always mean that someone is unhealthy. For example, some athletes may be considered overweight because of having developed muscles, which weigh more than fat, while still having a healthy level of body fat.

Obesity can take a major toll on your physical health, affecting virtually every organ and body system, including the musculoskeletal, cardiovascular, respiratory, digestive and reproductive systems. The good news is that losing even 5% to 10% of your weight can delay or prevent obesity-related diseases.

Obesity increases the risk for dangerous conditions, such as diabetes, heart disease, arthritis, and cancer. Seek prompt medical care if you experience weight gain. Following a medically recommended weight loss plan can help you reduce the risk of serious diseases associated with obesity.


What are the symptoms of obesity?

General symptoms of obesity include weight gain, needing to buy progressively larger-sized clothing, and a change in the shape of your body due to the accumulation of excessive fat. In men, excessive fat stores tend to accumulate in the waist. In women, extra fat is often stored in the hips and thighs. However, in both sexes, extra fat can accumulate throughout the body, including areas such as the face, neck, feet and hands.

Body mass index and other tests

A medical sign of obesity or overweight is having a higher than normal body mass index (BMI). BMI is one method used by health care professionals to calculate an estimate of the amount of body fat you are carrying. BMI is accurate for most people, but may not be an accurate indicator of excessive fat stores for certain populations.

For example, if you are an athlete with developed muscles, which weigh more than fat, you may have a healthy level of body fat but still rank as overweight on the BMI. Also, BMI is not accurate in determining fat stores in pregnant women and people with diseases that cause moderate to large amounts of water retention.

While a high BMI identifies potential weight issues, it is not diagnostic and will not indicate any specific health risks. To better determine the risk of developing weight-related health problems, other indicators are assessed by health care providers. These include:

  • Obesity-related diseases and conditions, such as high blood pressure or a sedentary lifestyle, and other factors

  • Waist size; excessive fat in the waistline is associated with an increased risk for obesity-related diseases, such as diabetes


What causes obesity?

Obesity is caused by consuming more calories than necessary to fuel your body’s activity level and metabolic processes in a given time period. Extra calories are stored as fat if there is not a corresponding increase in exercise to burn calories. Primary causes of an increase in stored body fat include:

  • Diets that are high in calories, fat and sugar

  • Sedentary lifestyle without sufficient exercise

Less often, obesity may be directly or indirectly caused by certain untreated diseases or conditions including:

  • Certain medications, such as corticosteroids, antidepressants, and seizure medications

  • Cushing's syndrome (overproduction of the hormone cortisol)

  • Hypothyroidism (underactive thyroid)

  • Polycystic ovarian syndrome (PCOS, which produces high levels of certain hormones )

What are the risk factors for obesity?

There are many factors that may encourage, influence or contribute to the development of obesity. These factors may occur alone or may be linked with other factors, such as aging in combination with a sedentary lifestyle. Factors that can increase the risk of obesity include:

  • Aging, which slows metabolism and the rate at which you burn calories

  • Cultural factors, such as overeating or eating high-calorie foods as a part of certain cultural practices or gatherings

  • Eating a diet that is high in calories, fat and sugar. Your caloric intake may be influenced by the easy accessibility of super-sized, high-calorie foods, which also tend to be less expensive and more convenient than healthier foods.

  • Family history of obesity. Obesity tends to run in families, which may be linked to both genetics and the development of similar dietary and exercise habits.

  • Insomnia or poor sleep habits

  • Menopause

  • Pregnancy

  • Poor socioeconomic status. People from low-income backgrounds have a greater risk for obesity.

  • Sedentary lifestyle

  • Smoking cessation. Some people who quit smoking gain weight. After quitting smoking, the sense of taste and smell improves, which may encourage some people to overeat.

  • Stress, depression, anxiety, and other mental and emotional disturbances

  • Weight gain during pregnancy that is not lost after giving birth

  • Working night shifts or odd shifts and getting poor-quality sleep


How is obesity treated?

In most cases, obesity in adults and children results from consuming too many calories and not getting enough physical activity. Treatment of obesity includes developing and following a sensible, comprehensive lifelong plan to reduce your caloric intake while ensuring good nutrition and hydration, and increasing physical activity. Effective plans often incorporate some form of support through a medically approved weight-loss group or organization, such as Weight Watchers. Counseling may also be recommended to help you change certain behaviors or address issues that lead you to overeat, such as anxiety and depression.

In general, it is advised that you lose no more than one to two pounds a week to achieve a safe, healthy weight loss that can be maintained. Recommended calorie intake and exercise levels will vary among individuals, depending on age, sex, general fitness level, medical history, and other factors. Very low-calorie diets or diets that are not well-balanced are generally not recommended because they can lead to rebound weight gain, poor nutrition, and other health problems.

Consult with your health care provider before starting any weight reduction plan so that he or she can monitor health conditions, such as blood pressure and blood sugar levels, and help you develop the most effective, safe and healthy weight-loss plan for you.

Medications used to treat obesity

When a comprehensive diet and exercise program is not enough to help a severely obese person lose weight, medications or surgery may be an option to help treat obesity. You should not take any weight-reduction medications, supplements, or herbal preparations without first consulting with your physician or health care provider. Over-the-counter products may cause serious side effects or interactions with the medications you take and many have not been tested by the Food and Drug Administration (FDA) to prove they are safe or effective.

Weight-loss medications approved by the FDA include:

  • Orlistat (Xenical), which reduces the absorption of fats, fat calories, and vitamins A, D, E and K by the body

  • Alli, an over-the-counter, low-dose form of orlistat, which is taken along with a reduced-calorie, low-fat diet and increased physical activity

Note that rare cases of liver injury or liver failure have been reported with both forms of orlistat.

Surgical procedures used to treat obesity

Weight-loss surgery, or bariatric surgery, may help some seriously obese people who have not lost weight by attempting lifestyle and dietary changes, or who have serious complications of obesity, such as type 2 diabetes or cardiovascular disease. Typically, these procedures target the gastrointestinal (GI) tract, reducing the amount of absorbable nutrients. The most common surgical methods include:

  • Gastric band, or LAP-BAND, involves placing a band around the upper portion of the stomach to make a smaller pouch for food, which limits how much food you can eat and makes you feel full sooner.

  • Roux-en-Y gastric bypass involves creating a small stomach pouch with a bypass around part of the small intestine, which is where most calories are absorbed.

What are the potential complications of obesity?

Complications of obesity can be serious, even life threatening. You can treat obesity and minimize the risk of complications by following the treatment plan you and your health care professional design specifically for you. Potential complications of obesity include:

Was this helpful?
Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2016 Nov 23
  1. Overweight and Obesity. Centers for Disease Control and Prevention. http://www.cdc.gov/obesity/.
  2. Obesity. Medline Plus, a service of the National Library of Medicine National Institutes of Health. http://www.nlm.nih.gov/medlineplus/obesity.html.
  3. How Are Overweight and Obesity Treated? National Heart Lung and Blood Institute. National Institutes of Health. http://www.nhlbi.nih.gov/health/dci/Diseases/obe/obe_treatments.html
  4. Moyer VA, U.S. Preventive Services Task Force. Screening for and management of obesity in adults: U.S. Preventive Services Task Force recommendation statement. Ann Intern Med 2012; 157:373.
  5. Domino FJ (Ed.) Five Minute Clinical Consult. Philadelphia: Lippincott Williams & Wilkins, 2013.
Explore Weight Loss Surgery
Recommended Reading
Next Up
Answers to Your Health Questions
Trending Videos