Key Points
- Diet and exercise coupled with behavioral modification can improve both patient-related and disease-related outcomes in the short term; however, long-term efficacy is lacking (A).
- Drugs such as sibutramine or orlistat may achieve modest, short-term weight loss, but their long-term effectiveness is unproven (A).
- For patients with a BMI >40, gastric bypass procedures can lead to long-term weight loss (B).
Physician intervention to encourage and assist obese patients to lose weight is warranted, for these reasons:
- Prevention of adverse outcomes. Left untreated, obesity is clearly related to the development of many adverse health outcomes, including diabetes mellitus, hypertension, stroke, hyperlipidemia, coronary artery disease, gallstones, osteoarthritis, obstructive sleep apnea, vascular disease, depression, and certain cancers (breast, endometrial, prostate, colon).1-4
- Reduction of morbidity and mortality. A causal effect between intentional weight loss and mortality has been difficult to prove, but even modest weight loss can reduce the morbidity of obesity-related disease, such as arthritis and obstructive sleep apnea (Strength of recommendation: A).5-7 For those at increased risk of death from cardiovascular disease, such as persons with obesity and diabetes mellitus, intentional weight loss coupled with lifestyle change can significantly reduce mortality (SOR: C).8 Nearly 280,000 deaths per year are attributable to obesity.9
- Cost reduction. Nearly 25% of American adults are obese, and more than half are overweight.1,2 Obesity burdens society with significant costs, including more than $50 billion annually for direct care. With an additional $30 billion spent each year on weight-loss products and services, this disease accounts for over 5% of annual health care expenditures in the United States.5
Nature or nurture?
Excess fat is created when energy intake exceeds cellular energy consumption. The complex relationship between the human body’s environment and the development of obesity is poorly understood, but recent genetic investigations have elucidated new mechanisms in the regulation of both satiety and energy expenditure. Using data from heritability studies, some researchers have estimated that up to 70% of the variability in weight among humans can be explained by genetic influences, but it is unlikely that changes in human genes account for the recent change in obesity prevalence.10
Risk factors
Identifiable risks factors for obesity in adulthood include parental history of obesity, low socio-economic background, and a history of high birth weight.11
Prevention
Recently, factors including consumption of sugar-sweetened beverages, lack of breast-feeding, and television viewing have been identified as risk factors for childhood and adolescent obesity.12-14 Because obesity at a young age can lead to adult obesity, these factors may be targeted to prevent adult obesity.
School-based programs for diet and exercise appear to be ineffective for preventing obesity (SOR: B).15,16 However, most research has been of limited quality. In one recent randomized study, reduction of television viewing (including videotape and videogame use) through school intervention was associated with significant reduction in BMI (SOR: B).14
Screening recommendations
The United States Preventive Service Task Force recommends periodic measurement of both height and weight in adults (SOR: B). The waist-to-hip ratio is thought to have insufficient evidence for recommendation as a routine screening tool because studies identifying a benefit to screening using only the waist-to-hip ratio have not been completed (SOR: C).17
Initial determination of obesity
Although the standard for body fat measurement is densitometry, which determines the density of a body submersed in water, the cost and technical requirements prohibit routine use in the clinical setting.18-20 The waist-to-hip ratio and waist circumference are used to identify central (or android) obesity in which adipose tissue in the abdomen is associated with atherosclerosis.21,22 The waist circumference is found by measuring the circumference around the waist at the level of the iliac crest. Values above 40 inches for men and 35 inches for women are indicative of increased risk of adverse health outcomes.5,19 The waist-to-hip ratio is calculated by dividing the circumference of the waist at the level of the L3 by the hip circumference measured at the largest area of the gluteal region.19 For men, waist-to-hip ratios greater than 1.0 are associated with significantly increased risk of cardiovascular events. For women, a ratio greater than 0.85 indicates increased risk.19
Body-mass index calculation
The body-mass index (BMI), also known as the Quetelet index, is the most commonly used measure of obesity.20 BMI is a patient’s weight in kilograms divided by his or her height in meters squared (kg/m2 ).5,19 A free online BMI calculator is available through the National Heart, Lung and Blood Institute at www.nhlbisupport.com/bmi/bmicalc.htm.
Although the BMI estimates total body fat and compares well with densitometry, it may be less accurate in selected populations (eg, the elderly, certain ethnic groups, and persons with large muscle mass).19 Generally, when BMI exceeds 25, the greater the BMI, the greater the obesity-related morbidity and mortality.5,19,20,23 Table 1 shows the classification of obesity based on BMI, and Table 2 shows the BMI for combinations of height and weight in inches and pounds.5