Obesity and Weight Loss Surgery

Learn more about weight loss surgery

Reviewed by Neil Hutcher, MD

Obesity is a disease that affects 34 percent of adults age 20 and over in the United States, which amounts to more than 72 million people. About 33.3 percent of American men and about 35.3 percent of American women are obese.*

The number of overweight and obese Americans has increased almost continuously since 1960. About 66 percent of U.S. adults were estimated to be either overweight or obese by the 2003-2004 National Health and Nutrition Examination Survey.

The rate of obesity differs from state to state, which is probably a reflection of various lifestyle, age and economic factors. The rankings below are based on data from 2004 to 2006.

Obesity rates among U.S. adults

If you are obese, you may have inherited it, because it has a strong genetic component. Your environment is another contributor. Our culture fosters the tendency toward obesity: physical activity isn't often required in our society, and the foods that cost the least often contain the most calories and the fewest nutrients.

There are a number of dangerous consequences. Obesity increases your risk of developing high blood pressure, type 2 diabetes, heart disease, stroke, gallbladder disease, cataracts, age-related macular degeneration (AMD) and cancer of the breast, prostate, and colon. In fact, obesity increases your risk of death.

About 3 percent of Americans, or 6.8 million adults, were morbidly obese in 2005, according to the non-profit think tank Rand Corporation. (In the Rand study, "morbidly obese" was defined as having a body mass index or BMI of 40 or higher. Read more about BMI below.)

You don't have to be skinny to reduce these risks. If maintained, even weight losses as small as 10 percent of body weight can improve your health.

Measuring Obesity with the Body Mass Index

How do we measure obesity? Body mass index (BMI) is a good indicator, because it correlates pretty well with the amount of body fat a person has. BMI is a formula that calculates the ratio between height and weight:

  • Measuring using pounds and inches:
    (pounds of weight / [inches of height]2) x 703
    For example, if your weight is 170 lbs. and your height is 5'6" (66"), then the calculation is: (170 ÷ 662) x 703 = 27.4
  • Measuring using kilograms and meters:
    kilograms of weight / meters of height2
    For example, if your weight is 75 kg and your height is 162 cm (1.62 m), then the calculation is: 75 ÷ 1.622 = 28.6

If you don't want to do the math, use the handy calculator below.

The body mass index range for adults 20 and over is shown here:

BMIWeight Status
Below 18.5Underweight
18.5 - 24.9Normal
25.0 - 29.9Overweight
30.0 and aboveObese

Click here for information on the body mass index for children and teens.

Your physician can use your BMI to help determine if you have a weight problem. But a high BMI isn't enough information to determine a course of action. For example, healthy athletes may weigh more than other people of the same height because they have well-developed muscles; muscle tissue is denser than fat tissue, so a particular volume of muscle will weigh more than the same volume of fat.

Your doctor will need to evaluate your diet, how much exercise you get, your family history of disease and many other factors before determining the next step for you.

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Causes of Obesity

Knowing the various reasons that people become obese can help you understand your own struggle more clearly.

Whether you decide to have weight loss surgery or not, understanding your condition is vital for losing weight and keeping the weight off. Here are the most common causes of obesity:

  • Genetics: Obesity can often be traced to genes, and the brain can induce appetite tendencies.
  • Illness: Hypothyroidism, Cushing Syndrome and depression.
  • Psychology: Mental illness and emotional problems.
  • Lifestyle Habits: Poor diet and low levels of daily activity.

You may be able to lose weight and improve your health by addressing the causes of your obesity. But sometimes these attempts do not work without surgery. If you have been battling obesity and losing the battle, it may be time to consider bariatric surgery. To help you make a decision, talk to a qualified bariatric physician and surgeon.

Related Topics

*Source: National Health and Nutrition Examination Surveys 2005-2006, conducted by National Center for Health Statistics (Centers for Disease Control and Prevention)

[Page updated April 2008]