Obesity is now a true epidemic and public health crisis that both clinicians and patients must face. Normal body weight is defined as a body mass index (BMI), calculated as the weight in kilograms divided by the height in meters squared, of < 25 kg/m2; overweight is defined as a BMI = 25.0–29.9 kg/m2, and obesity as a BMI > 30 kg/m2. Over the last several years, the prevalence of obesity in the US population has increased dramatically. Among US adults, rates of obesity have risen from 15.9% in 1995 to 27.2% in 2009. There is significant variation in rates of obesity by race. Between 2006 and 2008, blacks (35.7%) had 51% greater prevalence of obesity and Hispanics (28.7%) had 21% greater prevalence when compared with non-Hispanic whites (23.7%). This trend has been linked both to declines in physical activity and to increased caloric intake in diets rich in fats and carbohydrates.
Adequate levels of physical activity appear to be important for the prevention of weight gain and the development of obesity. Despite this, only 49% of Americans are physically active at a moderate level and 20% at a more vigorous level. In addition, only 3% of Americans meet four of the five recommendations for the intake of grains, fruits, vegetables, dairy products, and meat of the Food Guide Pyramid. Only one of four Americans eats the recommended five or more fruits and vegetables per day.
Risk assessment of the overweight and obese patient begins with determination of BMI, waist circumference for those with a BMI of 35 or less, presence of comorbid conditions, and a fasting blood glucose and lipid panel. Obesity is clearly associated with type 2 diabetes mellitus, hypertension, hyperlipidemia, cancer, osteoarthritis, cardiovascular disease, obstructive sleep apnea, and asthma. One of the most important sequelae of the rapid surge in prevalence of obesity has been a dramatic increase in the prevalence of diabetes. Diabetes mellitus affects approximately 8% of the US population, and in 2010, 27% of US residents aged 65 years and older were diabetic. In addition, almost one-quarter of the US population currently has the metabolic syndrome, putting them at high risk for the development of CHD. Metabolic syndrome is defined as the presence of any three of the following: waist measurement of 40 inches or more for men and 35 inches or more for women, triglyceride levels of 150 mg/dL or above, HDL cholesterol level < 40 mg/dL for men and < 50 mg/dL for women, blood pressure of 130/85 mm Hg or above, fasting blood glucose levels of 100 mg/dL or above.
The relationship between overweight and obesity and diabetes, hypertension, and coronary artery disease is thought to be due to insulin resistance and compensatory hyperinsulinemia. Persons with a BMI ≥ 40 have death rates from cancers that are 52% higher for men and 62% higher for women than the rates in men and women of normal weight. Significant trends of increasing risk of death with higher BMIs are observed for cancers of the stomach and prostate in men and for cancers of the breast, uterus, cervix, and ovary in women, and for cancers of the esophagus, colon and rectum, liver, gallbladder, pancreas, and kidney, non-Hodgkin lymphoma, and multiple myeloma in both men and women.
In the Framingham Heart Study, overweight and obesity were associated with large decreases in life expectancy. For example, 40-year-old female nonsmokers lost 3.3 years and 40-year-old male nonsmokers lost 3.1 years of life expectancy because of overweight, and 7.1 years and 5.8 years of life expectancy, respectively, because of obesity. Obese female smokers lost 7.2 years and obese male smokers lost 6.7 years of life expectancy compared with normal-weight smokers, and 13.3 years and 13.7 years, respectively, compared with normal-weight nonsmokers. Clinicians must work to identify and provide the best prevention and treatment strategies for patients who are overweight and obese. Patients with abdominal obesity (high waist to hip size ratio) are at particularly increased risk. Control of visceral obesity in addition to other cardiovascular risk factors (hypertension, insulin resistance, and dyslipidemia) is essential to reducing cardiovascular risk.
Prevention of overweight and obesity involves both increasing physical activity and dietary modification to reduce caloric intake. Clinicians can help guide patients to develop personalized eating plans to reduce energy intake, particularly by recognizing the contributions of fat, concentrated carbohydrates, and large portion sizes (see Chapter 29). Patients typically underestimate caloric content, especially when consuming food away from home. Providing patients with caloric and nutritional information may help address the current obesity epidemic. To prevent the long-term chronic disease sequelae of overweight or obesity, clinicians must work with patients to modify other risk factors, eg, by smoking cessation see above) and strict blood pressure and glycemic control (see Chapters 11 and 27).
Lifestyle modification, including diet, physical activity, and behavior therapy has been shown to induce clinically significant weight loss. Other treatment options for obesity include pharmacotherapy and surgery. In overweight and obese persons, at least 60 minutes of moderate- high intensity physical activity may be necessary to maximize weight loss and prevent significant weight regain. Counseling interventions or pharmacotherapy can produce modest (3–5 kg) sustained weight loss over 6–12 months. Counseling appears to be most effective when intensive and combined with behavioral therapy. Pharmacotherapy appears safe in the short term; longterm safety is still not established. Lorcaserin, a selective 5-hydroxytryptamine (5-HT) (2C) agonist, has been shown to reduce body weight through a reduction of energy intake without influencing energy expenditure; however, it is not yet approved by the US Food and Drug Administration (FDA).
In dietary therapy, a 2008 study comparing various diets revealed that Mediterranean (moderate fat, restricted calorie) and low-carbohydrate (non-restricted calorie) diets are effective alternatives to low-fat diets. In a randomized trial comparing low carbohydrate and low fat diets combined with behavioral treatment, there was no difference in weight loss at 2 years (7%). Commercial weight loss programs are effective in promoting weight loss and weight loss management. A randomized controlled trial of over 400 overweight or obese women demonstrated the effectiveness of a freeprepared meal and incentivized structured weight loss program compared with usual care.
Weight loss strategies using dietary, physical activity, or behavioral interventions can produce significant improvements in weight among persons with prediabetes and a significant decrease in diabetes incidence. Lifestyle interventions including diet combined with physical activity are effective in achieving weight loss and reducing cardiometabolic risk factors among patients with severe obesity.
Bariatric surgical procedures, eg, vertical banded gastroplasty and Roux-en-Y gastric bypass, are reserved for patients with morbid obesity whose BMI exceeds 40, or for less severely obese patients (with BMIs between 35 and 40)with high-risk comorbid conditions such as life-threatening cardiopulmonary problems (eg, severe sleep apnea, Pickwickian syndrome, and obesity-related cardiomyopathy) or severe diabetes mellitus. In selected patients, surgery can produce substantial weight loss (10 to 159 kg) over 1 to 5 years, with rare but sometimes severe complications. Nutritional deficiencies are one complication of bariatric surgical procedures and close monitoring of a patient’s metabolic and nutritional status is essential.
Clinicians seem to share a general perception that almost no one succeeds in long-term maintenance of weight loss. However, research demonstrates that approximately 20% of overweight individuals are successful at long-term weight loss (defined as losing ≥ 10% of initial body weight and maintaining the loss for ≥ 1 year). National Weight Control Registry members who lost an average of 33 kg and maintained the loss for more than 5 years have provided useful information about how to maintain weight loss. Members report engaging in high levels of physical activity (approximately 60 min/d), eating a low-calorie, low-fat diet, eating breakfast regularly, self-monitoring weight, and maintaining a consistent eating pattern from weekdays to weekends. The development and implementation of innovative public health strategies is essential in the fight against obesity.
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