Prevalence

Guideline recommendations used in this article have been adapted from

• An estimated 97 million adults in the United States, 55% of the population, are overweight or obese (body mass index [BMI] >25)1, 2
• The NHANES study of 1988-1994 indicated that 27% of females and 21% of males are obese (BMI >30)3
• The prevalence of obesity increased from 12% in 1991 to 18% in 1998. Increases were seen in both sexes and all socioeconomic classes, with the greatest increase seen in 18- to 29-year-olds and in those who have achieved higher education4
• Obesity rates are underestimated because overweight people tend to underestimate their weight and overestimate their height5

Etiology

• Obesity is a chronic condition that develops as a result of an interaction between a person's genetic makeup and their environment. How and why obesity occurs are not well understood; however, social, behavioral, cultural, psychological, metabolic, and genetic factors are involved1
• Among possible hormones involved, leptin, discovered in 1994, has received the most attention. Leptin appears to regulate adipose proliferation and modulate eating behavior.6 A 1999 study showed that subcutaneous therapy with recombinant leptin produced weight loss in both obese and lean subjects7
• Heritability studies indicate that genetic factors may be responsible for up to 70% of the variation in people's weight6
• Weight gain is dependent on a person's energy intake being greater than energy expenditure. One pound (0.45 kg) is equal to 3,500 calories. Therefore, a person consuming 500 calories more than he or she expends daily will gain 1 lb a week
• A person's body weight tends to range within 10% of a set value. Weight alterations in either direction cause changes in energy expenditure that favor a return to the set-point.8 This mechanism helps explain the terrible problem of recidivism following attempted weight loss

Complications

• Relative risk9 (p78) greater than 3,
  Type 2 diabetes mellitus, gallbladder disease, hypertension, hyperlipidemia, and sleep apnea
• Relative risk 2 to 3
  Coronary artery disease, knee osteoarthritis, and gout
• Relative risk 1 to 2
  Breast, endometrial, or colon cancer; low back pain
  The relationship between obesity and comorbidities is stronger among individuals younger than 55 years.10 After age 74, there is no longer an association between increased BMI and mortality11
• Hypertension is the most common obesity-related disease. Hypertension and weight class are strongly associated in persons younger than 55 years (see below for definitions of weight class)12
• About 80% of people with type 2 diabetes are obese
• Hypercholesterolemia is prevalent in obese persons, but its incidence does not increase with increasing weight class. The incidence of diabetes, osteoarthritis, and gallbladder disease increases as weight increases
• The prevalence of cardiovascular disease is significantly elevated for obesity class 1 in males and for all three obesity classes in females

• Diet and exercise have been shown to be ineffective over the long term. More than 90% of people who attempt to lose weight gain it all back
• Even in clinical trials that demonstrate substantial weight loss, the lost weight tends to be regained once supervision concludes
• On the positive side, sustained weight loss has been shown to improve blood pressure and lipid and glucose levels
• A reasonable goal is to lose 10% of body weight over a 6-month period
• Patients with BMIs in the range of 27 to 35 should be encouraged to lose 0.5 to 1 lb a week at a daily calorie deficit of 300 to 500
• Patients with BMIs above 35 should lose 1 to 2 lb a week at a daily calorie deficit of 500 to 1,000

• A diet that is low in grains and sugar is needed to lose weight
• A healthy diet contains about 25% fat, 20% protein, and 55% carbohydrates
• Total caloric intake is determined by calculating basal energy expenditure and activity, then subtracting 500 calories to result in a weight loss of 1 lb a week
• This usually means a diet of 1,000 to 1,200 kilocalories (kcal) per day for women and 1,200 to 1,500 kcal per day for men
• Patients should be educated by a registered dietitian to eat a diet individualized to their needs

• Physical activity is a necessary component of every weight loss plan. Exercise contributes to weight loss and maintenance, may decrease abdominal fat, and increases cardiorespiratory fitness
• Initial exercise goal: moderate activity for 30 to 45 minutes 3 to 5 days a week
• Long-term exercise goal: at least 30 minutes of moderate to intense exercise per day1
• Behavior therapy: advice for patients
• Eat three meals a day at about the same time each day sitting at a table
• Focus on the meal. Eat slowly. Avoid distractions such as television or magazines
• Cook small amounts; use small plates
• Avoid second helpings. Clean plates directly into the garbage

Abstracted from Western Journal of Medicine January 2002;176:23-28