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Diane is a 35-year-old woman who has struggled with obesity for most of her life. Her current body mass index (BMI) is 36. She has tried “every kind of diet you can imagine” but has always gotten stuck after losing the first 10 pounds and gets discouraged. She is not currently exercising regularly. She is concerned about all the skin tags on her neck and wants them removed if possible. She and her husband are talking about having another baby and she would like to be in better shape before she attempts pregnancy. She wants to discuss risks of pregnancy considering her weight and asks for any advice that you can give her on how to successfully lose weight. You obtain a random blood sugar because of the acanthosis and obesity (Figure 224-1). The result is 150 mg/dL and you order a fasting blood sugar (FBS) before her next visit, at which time you will remove her skin tags. After discussing diet and exercise, you encourage her to pursue Weight Watchers or a similar program.

Figure 224-1

Neck circumference enlargement with acanthosis nigricans and many skin tags in a woman with obesity and impaired glucose tolerance. (Courtesy of Richard P. Usatine, MD.)

Obesity is defined as a BMI greater than or equal to 30. BMI is calculated as weight in kilograms divided by height in meters squared, rounded to 1 decimal place.1 Obesity in children is defined as a BMI greater than or equal to the age- and sex-specific 95th percentiles of the 2000 Centers for Disease Control and Prevention (CDC) growth charts. Adults with a BMI greater than 40 have substantially more serious health consequences, including heart disease and diabetes, and a reduced life expectancy.

  • Based on the National Health and Nutrition Examination Surveys, more than one-third of U.S. adults (35.7%) and 16.9% of children and adolescents are obese (2010).1 Slightly more women than men are obese (35.8% vs. 35.5%), although obesity is more prevalent in boys than girls at ages 2 to 19 years (18.6% vs. 15%). The prevalence of obesity has dramatically increased over the past 20 years.
  • At the 6-year follow-up of the Nurses' Health Study (NHS; a prospective cohort study of 50,277 women), 3757 (7.5%) women who had a BMI of less than 30 in 1992 became obese (BMI ≥30).2
  • The medical care costs of obesity in the United States (2008 dollars) are approximately $147 billion.3

Obesity is a complex problem involving genetics, health behaviors, environment, and sometimes medical diseases (see “Differential Diagnosis” below) or drugs (e.g., steroids, antidepressants). The ­simplest explanation of obesity is an imbalance between intake (calories eaten) and output (physical activity).


The genetic contribution to interindividual variation in common obesity has been estimated at 40% ...

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