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 less than 25; overweight is defined as a BMI = 25.0–29.9, and obesity as a BMI greater than 30. BMI is often miscategorized as overweight, when it is in fact in the obese range.
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. In addition, almost one-quarter of the US population currently has the metabolic syndrome. 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 (1.70 mmol/L) or above, HDL cholesterol level less than 40 mg/dL (less than 1.44 mmol/L) for men and less than 50 mg/dL (less than 1.80 mmol/L) for women, blood pressure of 130/85 mm Hg or above, and fasting blood glucose levels of 100 mg/dL (5.55 mmol/L) 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.
Obesity is associated with a higher all-cause mortality rate. Data suggest an increase among those with grades 2 and 3 obesity (BMI more than 35); however, the impact on all-cause mortality among overweight (BMI 25–30) and grade 1 obesity (BMI 30–35) is questionable. Persons with a BMI of 40 or higher 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.
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.
Prevention of overweight and obesity involves both increasing physical activity and dietary modification to reduce caloric intake. Adequate levels of physical activity appear to be important for the prevention of weight gain and the development of obesity. Physical activity programs consistent with public health recommendations may promote modest weight loss (~2 kg); however, the amount of weight loss for any one individual is highly variable.
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 and obesity, clinicians must work with patients to modify other risk factors, eg, by smoking cessation (see previous section on cigarette smoking) 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 (see Chapter 29). 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; long-term safety is still not established.
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 free prepared 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, adjustable gastric band, sleeve gastrectomy, 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 (10–159 kg) over 1–5 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.
Finally, 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% or more of initial body weight and maintaining the loss for 1 year or longer).
Clinicians must work to identify and provide the best prevention and treatment strategies for patients who are overweight and obese. Clinician advice on weight loss can have a significant impact on patient attempts to adjust weight-related behaviors. Unfortunately, many clinicians are poorly prepared to address obesity. Clinicians are more likely to give advice as BMI increases, missing opportunities to discuss weight with overweight patients. Clinician bias and lack of training in behavior-change strategies impair the care of obese patients. Strategies to address these issues should be incorporated into innovative treatment and care-delivery strategies (see Chapter 29).
et al. Guideline recommendations for obesity management. Med Clin North Am. 2018 Jan;102(1):49–63.
et al. Health advice and education given to overweight patients by primary care doctors and nurses: a scoping literature review. Prev Med Rep. 2019 Jan 25;14:100812.