Chapter 224. Obesity

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.

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).

Genetics

The genetic contribution to interindividual variation in common obesity has been estimated at 40% to 70%.4 Despite this relatively high heritability, the search for obesity susceptibility genes has been difficult. At least five variants in four candidate genes are associated with obesity-related traits. Although genome-wide linkage studies have been unable to pinpoint genetic loci for common obesity, high-density genome-wide association studies have discovered at least 15 previously unanticipated genetic loci associated with BMI and extreme obesity risk.4 Genetic influences, however, cannot explain the recent increased prevalence in the rate of weight gain by age; rather significant changes in lifestyle factors are likely responsible.5

• Two GI “hormones” that appear to integrate into the brain may regulate appetite; these hormones—ghrelin (increases appetite) and obestatin (slows gastric emptying, blocking ghrelin action)—may also play a role in obesity. A metaanalysis concluded that obestatin and total and active ghrelin were significantly higher in normal weight subjects than those of obese groups.6 It is not clear why this occurs but lower levels of ghrelin in obese subjects may be a response to hyperinsulinemia.

Health Behaviors

Lifestyle factors associated with obesity include physical activity level (low levels and associated behaviors such as television viewing), diet, and sleep.

• In the NHS, each 2-hour per day increment in TV watching was associated with a 23% (95% confidence interval [CI], 17% to 30%) and each 2-hour per day increment in sitting at work was associated with a 5% (95% CI, 0% to 10%) increase in obesity.2
• Based on second-wave interview data from the National Longitudinal Study of Adolescent Health (N = more than 14,000 adolescents), increasing levels of vigorous physical activities lowered the risk for obesity among all adolescents, while eating sufficient fruits and vegetables was inversely associated with adolescents' obesity.5 As in the above study, sedentary lifestyle was associated with adolescents' obesity. However, in models based on race, low family socioeconomic status, and being sedentary were associated with overweight and obesity among whites and increased nighttime sleep hours was associated with obesity among African Americans.
• In one study, belief that obesity was inherited was associated with lower reported levels of physical activity and fruit and vegetable consumption while the belief that obesity was caused by lifestyle behaviors was associated with greater reported physical activity but not diet.7
• In a study of Latino men and women, men who did not exercise, rarely trimmed fat from meat, and ate fried foods the previous day were 16 pounds heavier than men with healthier habits.8 Women who had limited exercise (<2.5 hours per week), watched television regularly, ate chips and snacks, and ate no fruit the previous day were 45 pounds heavier than women with healthier habits.

Environment

Factors that have been discussed include location of grocery stores versus fast-food restaurants and safe places to exercise in relation to home proximity. Research studies suggest that neighborhood residents who have better access to supermarkets and limited access to convenience stores tend to have healthier diets and lower levels of obesity.9 Poor neighborhoods are often characterized by just the opposite. In fact, in one study, having the opportunity to move from a poor neighborhood to one with a lower level of poverty through housing vouchers was associated with modest reductions (4.6%) in the prevalence of extreme obesity and diabetes.10

• Family history of obesity.
• Diet—High calorie, low fruits and vegetables,11 snack foods, and fast-food consumption (obesity prevalence 24% of those going to fast-food restaurants less than once a week to 33% of those going 3 or more times per week).12
• Low levels of physical activity.

The diagnosis of obesity is based on a BMI greater than 30.

Clinical Features

• Although elevated weight alone is a risk factor for the development of hypertension, diabetes mellitus (DM), and heart disease, increased waist circumference confers additional morbidity risk (Figure 224-2).13
• Neck circumference enlargement (Figure 224-1) along with increased BMI and waist circumference are significant risk factors for obstructive sleep apnea and metabolic syndrome.14,15
• There is a strong direct correlation between epicardial fat and abdominal visceral adiposity with evidence supporting a role for epicardial fat in the pathogenesis of coronary artery disease.16
• Nonalcoholic fatty liver disease (NAFLD) is present in 57% of overweight individuals attending outpatient clinics compared to 98% of nondiabetic obese patients and in contrast to 10% to 30% of adults in the general population (see Chapter 61, Liver Disease).17
• Obesity is also associated with an increased risk of varicose veins (odds ratio [OR] 3.28; 95% CI 1.25 to 8.63) (see Chapter 52, Venous Insufficiency) (Figure 224-3).
• Skin conditions associated with obesity include acanthosis nigricans (Figures 224-1 and 224-4), eruptive xanthomas (Figure 224-5), hidradenitis suppurativa (Figure 224-6), and psoriasis (Figure 224-2). (see Chapters 115, Hidradenitis Suppurativa, 152, Psoriasis, 220, Acanthosis Nigricans, and 223, Hyperlipidemia and Xanthomas).

Laboratory Testing

Although no specific tests are suggested for patients with obesity, assessing a patient's cardiovascular risk status in addition to BMI, waist circumference, and a patient's motivation to lose weight may be helpful in planning treatment.13 Consider screening for DM and NAFLD.

The differential diagnosis of a patient with obesity includes the following medical conditions:

• Cushing syndrome—Caused by prolonged exposure to endogenous or exogenous glucocorticoids; in addition to truncal obesity, clinical features include moon facies, supraclavicular fat pads, buffalo hump, purple striae, proximal muscle weakness, and hirsutism. Diagnosis is confirmed with inappropriately high serum or urine cortisol levels.
• Polycystic ovary syndrome—Criteria include two of three of oligoovulation or anovulation, hyperandrogenism, and polycystic ovaries.
• Obesity is also a finding in many single-gene disorders such as Prader-Willi syndrome (abnormality of proximal arm of chromosome 15 with associated characteristics of obesity, hypotonia, mental retardation, short stature, hypogonadotropic hypogonadism, strabismus, and small hands and feet) and Bardet-Biedl syndrome (associated with truncal obesity, childhood-onset visual loss preceded by night blindness, and polydactyly).

The initial weight loss goal is to reduce body weight by approximately 10% from baseline over approximately 6 months.13 Additional weight loss can be attempted if this goal is achieved.

Nonpharmacologic

• Dietary changes may be useful. In a metaanalysis of long-term weight loss strategies in adults, however, dietary/lifestyle therapy provides less than 5 kg weight loss after 2 to 4 years.18 SOR A Commercial weight management services appear to be more effective and cheaper than primary care-based services led by specially trained staff (range: 4.4 kg [Weight Watchers] to 1.4 kg [general practice]).19 SOR A
• Exercise should be encouraged and can result in small weight losses and improvement in cardiovascular risk factors; greater intensity exercise results in additional small weight loss (weighted mean difference [WMD] approximately −1.5 kg).20,21 SOR A The addition of diet to exercise also increases weight loss (WMD −1 kg).
• Although data are limited, lifestyle interventions appear to reduce overweight in children.22 SOR B
• Behavioral and cognitive-behavioral strategies are also effective (WMD −2.5 kg and −2.3 kg, respectively), but are most effective when used in combination with diet and exercise (WMD [added cognitive-behavioral strategies] −4.9 kg).23 SOR A
• Behavioral strategies found to be effective include various forms of support, motivational interviewing, and reducing TV screen time.
• Both remote weight-loss support (study-specific website and e-mail) and in-person support during group and individual sessions along with remote support resulted in greater sustained weight loss at 24 months than the control group (−4.6 kg, −5.1 kg, and −0.8 kg, respectively).24
• A program entitled “High Five for Kids,” using motivational interviewing targeting television viewing, fast food, and sugar-sweetened beverage intake, was not effective in one randomized clinical trial (RCT) in reducing BMI at 1 year.25
• With respect to psychological interventions, of three interventions (usual care with quarterly primary care physician educational visits, brief lifestyle counseling, or enhanced brief lifestyle counseling including meal replacements) examined in adult patients with obesity, enhanced care was more effective than usual care for initial weight loss and sustained weight loss at 2 years (1.7 ± 0.7 and 4.6 ± 0.7 kg, respectively).26 SOR B

Medications

• In the 2005 systematic review by Douketis et al., pharmacologic therapy for obesity resulted in to 10-kg average weight loss after 1 to 2 years.18 SOR A An older Cochrane review of orlistat, sibutramine, and rimonabant found more modest but significant weight reduction (2.9 to 4.7 kg); conclusions were limited by high attrition rates.27
• The National Heart, Lung, and Blood Institute (NHLBI) Clinical Guideline recommends consideration of drug therapy approved by the FDA for long-term use as an adjunct to diet and physical activity for patients with a BMI of 30 with no concomitant obesity-related risk factors or diseases, and for patients with a BMI of 27 with concomitant obesity-related risk factors or diseases. SOR B The American College of Physicians (ACP) guideline also recommends that pharmacologic therapy may be offered to patients with obesity who fail to achieve their weight loss goals through diet and exercise alone. However, they recommend a discussion of the drugs' side effects, the lack of long-term safety data, and the temporary nature of the weight loss achieved with medications before initiating therapy.28
• Medication options include sibutramine, orlistat, phentermine, diethylpropion, rimonabant, fluoxetine, bupropion, and phentermine/topiramate. Most weight loss occurs in the first 6 months of treatment.29 Investigators conducting a phase III trial of phentermine/topiramate reported greater weight loss for two different strengths of the drug over placebo at 1 year (−8.1 kg [lower dose] and −10.2 kg [higher dose] and −1.4 kg [placebo]).30

Complementary and Alternative Therapy

• A number of therapies have been proposed to assist in weight loss, including herbal and nonherbal food supplements, homeopathy, hypnotherapy, acupuncture, and acupressure.31 Of these, only ephedra sinica and other ephedrine-containing dietary supplements had convincing evidence of small reductions in body weight over placebo.
• A systematic review of food supplements (e.g., guar gum, chromium, chitosan) for weight reduction by some of the same authors also failed to find evidence of a clinically relevant weight loss (WMDs in the range of no benefit to −1.7 kg) using these preparations.32

Surgery

Surgical therapy provides approximately 25 to 75 kg of weight loss after 2 to 4 years.18 According to the NHLBI guideline, weight loss surgery is an option for well-informed, carefully selected patients with clinically severe obesity (BMI 40 or 35 with comorbid conditions) when less-invasive methods of weight loss have failed and the patient is at high risk for obesity-associated morbidity or mortality.13 SOR B The 2005 ACP guideline concurred and again added that a doctor-patient discussion of surgical options should include the long-term side effects (e.g., vitamin B12 deficiency, incisional hernia, possible need for reoperation, gastritis, gallbladder disease, and malabsorption).28 In addition, they recommend that patients should be referred to high-volume centers with surgeons experienced in bariatric surgery.

Two types of surgical procedures (gastric banding and gastric bypass) are in current use; all induce substantial weight loss and serve to reduce weight-associated risk factors and comorbidities.

• In a Cochrane review, authors found that weight loss was greater from gastric bypass than vertical banded gastroplasty or adjustable gastric banding, but similar to isolated sleeve gastrectomy and banded gastric bypass.33 Compared to other interventions available, surgery has produced the longest period of sustained weight loss.
• In a metaanalysis of 8 trials with more than 44,000 patients, the authors concluded that bariatric surgery (both gastric banding and gastric bypass) reduced long-term all-cause mortality (OR = 0.70; CI, 0.59 to 0.84), although the risk reduction was smaller in the larger studies; gastric bypass had a greater effect than banding on cardiovascular mortality.34
• In addition to reduced weight, a retrospective study of severely overweight patients with noninsulin-dependent diabetes who were referred for consideration of a gastric bypass procedure showed that patients undergoing the surgical procedure had a decrease in mortality rate for each year of follow-up compared to those who did not undergo the procedure because of personal preference or refusal of insurance payment.35
• Bariatric surgery was also found to be cost-effective compared to other treatments for obesity.36 Authors identified several remaining questions to be answered, including the influence of surgery on quality of life, late complications leading to reoperation, duration of comorbidity remission, and resource use.
• Laparoscopic bariatric surgery may be safer than open surgery with respect to wound infection (relative risk [RR] 0.21; 95% CI, 0.07 to 0.65) and incisional hernia (RR 0.11; 95% CI, 0.03 to 0.35). Risks appear similar for reoperation, anastomotic leak, and all-cause mortality.37
• In one study, the rate of hospitalization in the year following gastric bypass surgery was more than double the rate in the preceding year (19.3% vs 7.9%). The most common reasons for admission prior to surgery were obesity-related problems (e.g., osteoarthritis, lower extremity cellulitis) and elective operation (e.g., hysterectomy). The most common reasons for admission after gastric bypass surgery were complications thought to be procedure related, such as ventral hernia repair and gastric revision.38
• In a study of 16,155 Medicare beneficiaries who underwent bariatric procedures (mean age: 47.7 years [standard deviation (SD): 11.3 years]; 75.8% women), the rates of 30-day, 90-day, and 1-year mortality were 2.0%, 2.8%, and 4.6%, respectively. After adjustment for sex and comorbidity index, the odds of death within 90 days were 5-fold greater for older Medicare beneficiaries (age 75 years or older; n = 136) than for those age 65 to 74 years (n = 1381; OR 5.0; 95% CI, 3.1 to 8.0). The odds of death at 90 days were 1.6 times higher (95% CI, 1.3 to 2.0) for patients of surgeons with less than the median surgical volume of bariatric procedures.39

Referral

The Endocrine Society recommends that patients following bariatric surgery should receive care from a multidisciplinary team, including an experienced primary care physician, endocrinologist, or gastroenterologist. Primary providers should also consider enrolling patients postoperatively in a comprehensive program for nutrition and lifestyle management to prevent and detect nutritional deficiencies.40

• In one recent study, although a behavioral intervention (face-to-face visit; weekly mailed materials promoting appropriate weight gain, healthy eating, and exercise; individual weight gain graphs; and telephone-based feedback) was able to reduce the number of women with excessive weight gain in pregnancy by approximately 10%,41 authors of a systematic review found insufficient quality data from four earlier trials to provide evidence-based recommendations.42
• A behavioral approach of lifestyle counseling from nurse practitioners was not effective compared with usual care in preventing weight gain in overweight or obese adults, although approximately 60% of patients in both groups achieved weight maintenance after 3 years.43
• Authors of a Cochrane review of 37 studies found strong evidence to support beneficial effects of child obesity prevention programs on BMI, particularly for programs targeting children age 6 to 12 years.44 However, the overall effect was small (−0.15 kg/m2 [95% CI, −0.21 to −0.09).
• The United States Preventive Services Task Force (USPSTF) recommends that clinicians screen children age 6 years and older for obesity and offer them or refer them to comprehensive, intensive behavioral interventions to promote improvement in weight status.45 SOR B This recommendation is based in part on data showing that moderate- to high-intensity programs (>25 hours of contact with the child and/or the family over a 6-month period) improve weight status primarily in children with obesity.
• For adults, the USPSTF recommends that clinicians screen all adult patients for obesity and offer intensive counseling and behavioral interventions to promote sustained weight loss for obese adults.46 SOR B Evidence, however, was insufficient to recommend for or against the use of moderate- or low-intensity counseling together with behavioral interventions to promote sustained weight loss in obese adults or use of counseling of any intensity and behavioral interventions to promote sustained weight loss in overweight adults.

Obesity increases the risk in adults for the following:13,47

• Chronic health diseases such as coronary heart disease, type 2 DM, stroke, osteoarthritis, liver disease, and gallbladder disease.
• Cancers (i.e., endometrial, breast, colon, gallbladder).
• Cardiovascular risk factors such as hypertension and dyslipidemia.
• Sleep apnea and respiratory problems.
• Gynecologic problems (e.g., abnormal menses, infertility).

Overweight adolescents are also more susceptible than their leaner peers to hypertension, type 2 DM, dyslipidemia, lung problems (e.g., asthma, obstructive sleep apnea), orthopedic problems (e.g., genu varum, slipped capital femoral epiphysis), and nonalcoholic steatohepatitis.48,49 Obese adolescents may also suffer from depression and low self-esteem.49 In addition, more than half of obese adolescents remain overweight as young adults.49

Among pregnant women, obesity increases the risk for prenatal complications (gestational diabetes and hypertensive disorders),50 intrapartum complications (cesarean section, induced preterm birth),51 and stillbirth (OR 2.8; 95% CI, 1.5 to 5.3) and neonatal death (OR 2.6; 95% CI, 1.2 to 5.8) compared with women of normal weight.52 In addition, women whose gestational weight gain is above the recommendations retain an additional 3 kg after 3 years and 4.7 kg on average after 15 or more years postpartum.53

Based on one metaanalysis, intentional weight loss did not confer benefit on all-cause mortality but may provide a small benefit for individuals classified as unhealthy (those with obesity-related risk factors).54

• The NHLBI recommends frequent contacts between the patient and provider to promote and monitor weight loss and weight maintenance therapies.13 SOR C Although these programs can be conducted by a practitioner without specialization in weight loss, various health professionals with expertise are available and are often helpful.
• For children, health providers should calculate and plot BMI (or weight percentile) yearly and watch for excessive weight gain compared with linear growth, identify and track patients at risk of obesity based on risk factors, encourage and support breastfeeding, routinely promote healthy diets and levels of physical activity, and monitor changes in obesity-associated risk factors.49

• Advise patients to strive for a healthy lifestyle with a diet that is high in fruits and vegetables and to pursue daily physical activity. Maintaining normal weight and treating obstructive sleep apnea and diabetes may help prevent NAFLD.
• Weight loss can improve cardiovascular risk factors. Commercial weight-reduction programs may be most helpful.19 The addition of cognitive-behavioral strategies may enhance weight loss.23
• For patients who are obese and fail to achieve their weight loss goals through diet and exercise alone, pharmacologic therapy can be considered, but pharmacologic therapy adds cost, can be associated with adverse effects, lacks long-term safety data, and weight loss may be temporary.
• Surgery is also an option for carefully selected patients with clinically severe obesity (BMI 40 or 35 with comorbid conditions) when less-invasive methods of weight loss have failed and the patient is at high risk for obesity-associated morbidity or mortality.

Patient Resource

• Medline Plus. Obesity—http://www.nlm.nih.gov/medlineplus/obesity.html.

Provider Resources

• NHLBI. Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults (1998 guideline, BMI calculator, tip sheet, evidence tables)—http://www.nhlbi.nih.gov/guidelines/obesity/ob_home.htm.
• Centers for Disease Control and Prevention. Overweight and Obesity—http://www.cdc.gov/obesity/index.html.