Jeanne M. Clark
Epidemiology
Prevalence
Obesity, a state of excess body fat, has reached epidemic proportions in the United States and is increasing throughout the world. During the period 1988 to 1992, 33% of U.S. adults were overweight, 23% were obese, and 3% were extremely obese (1). Despite various efforts to treat and prevent obesity, by 2002, 45% of adults were overweight, and the prevalence of obesity was 30%, with 5% of adults beingextremely obese (2). No longer just an “American problem,” obesity is also becoming common in developed and developing countries throughout the world.
Obesity is not evenly distributed across the U.S. population, but differentially affects groups of different races, ethnicities, and educational and socioeconomic attainment. Overall, women are more likely to be obese than men. Among women, the prevalence of obesity is 31% among non-Hispanic whites, 38% among Mexican Americans, and 49% among non-Hispanic blacks. Obesity is also more common in women with lower educational and economic attainment (3). Men are more likely to be overweight than women, and the prevalence of overweight differs among the different racial/ethnic groups, with Mexican American men (75%) having the highest prevalence, followed by non-Hispanic whites (67%) and non-Hispanic blacks (61%). However, the prevalence of obesity among men is similar across the racial/ethnic groups (27% to 29%).
Etiology
Weight gain, and thus obesity, occurs when caloric intake exceeds caloric expenditure. However, the nuances of energy balance and its regulation are quite complex. Current theories include interplay between genetic predisposition, environment, and social/cultural role of food and activity, as well as the intricate interactions among various hormones, cytokines (e.g., tumor necrosis factor α), and adipokines (e.g., leptin, adiponectin). Currently, these have little or no clinical relevance except as noted below. Although binge-eating disorder is a relatively common problem among people seeking to lose weight, it is not a common cause of obesity. Although most people with this disorder are not obese, they do tend to be overweight.
Genes and the Environment
It has been estimated that 30% to 40% of obesity is attributable to a genetic predisposition, and 60% to 70% is attributable to the environment. Most of the genetic predisposition is polygenic, that is, it is controlled by several different genes, rather than a single gene mutation (monogenic). The one known exception is leptin deficiency, which occurs very rarely and results in severe obesity in childhood. Several mutations in this gene have been described and the patients generally respond to leptin treatment (4). More often, among those genetically predisposed, obesity occurs only under “adverse” conditions, such as high-calorie diets and sedentary lifestyle. These conditions, recently named the “toxic environment,” are thought to explain much of the rapid increase in the prevalence of obesity over the past few decades.
Medical Causes of Obesity
There are a number of medical conditions that can lead to weight gain and/or adipose accumulation. Hypercortisolism resulting from Cushing disease can result in adipose accumulation and redistribution. Rarely is this severe enough to cause obesity de novo, and the pattern of fat deposition and associated signs and symptoms are usually recognizable. Similarly, hypothyroidism can cause some weight gain, but is rarely the cause of obesity by itself. Other putative causes of obesity include hyperinsulinemia
P.1424
and polycystic ovary syndrome. However, whether these are causes or consequences of obesity is a matter of some debate. An accurate history and physical examination can distinguish whether such conditions are the underlying cause of weight gain. In general, extensive laboratory testing to identify an underlying cause for obesity is not needed.
A number of medications, including phenothiazines, lithium, glucocorticoids, insulin, insulin secretagogues (i.e., sulfonylureas), and anticonvulsants, can cause weight gain and may exacerbate or cause obesity. An accurate history of the weight trajectory and its relation to new medication can identify the problem. Unfortunately, in some cases, changing the offending medication may not be possible.
Sequelae of Obesity
Increased Mortality
Although mortality directly resulting from obesity can be difficult to separate from that attributable to coexisting conditions (e.g., diabetes, hyperlipidemia, coronary artery disease), the estimated number of deaths attributable to obesity in the United States ranges from 112,000 to 400,000 per year, making obesity an important cause of preventable deaths (5,6). Obese individuals have higher rates of death from all causes (7), and very obese young adults have a life expectancy that is up to 20 years shorter than nonobese adults (8). Furthermore, although generally thought to be associated with deaths from cardiovascular disease and diabetes, obesity is also associated with higher rates of death overall from cancer, and for most specific types of cancer (9).
Medical Consequences
Obesity is also associated with an increased risk of many diseases. Among obese adults, the relative risk of developing hypertension or diabetes is about three times that of people who are not obese; and for hypercholesterolemia it is 1.5 times. Furthermore, obesity independently increases the risk of coronary artery disease, stroke, obstructive sleep apnea, cholelithiasis, osteoarthritis, venous thrombosis, nonalcoholic fatty liver disease, gout, and cancers of the colon, rectum, and prostate in men, and of the uterus and gallbladder in women (10, 11, 12). Although there has been a great deal of research into the potential psychiatric consequences of obesity, at this time the bulk of the evidence suggests that obesity does not cause psychiatric conditions such as depression or anxiety. Table 83.1 lists the medical consequences of obesity.
In addition to these comorbidities, obesity also increases the morbidity and mortality from unrelated illnesses. For instance, obese persons with liver diseases such as hepatitis C, or alcohol-induced liver disease, have a poorer prognosis than nonobese persons. The impact of
P.1425
obesity on seemingly unrelated conditions is difficult to measure, but deserves consideration.
|
TABLE 83.1 Medical Consequences of Obesity |
||
|
Obesity, especially abdominal adiposity (waist circumference >40 inches in men and >35 inches in women), is strongly associated with a number of other adverse health conditions that form the “metabolic syndrome.” Widely believed to reflect a state of insulin resistance, this constellation includes elevated blood pressure (>130/85 mm Hg) and triglycerides (≥150 mg/dL), low high-density lipoprotein (HDL) cholesterol (<40 mg/dL for men, <50 mg/dL for women), and impaired glucose tolerance (fasting glucose ≥110 mg/dL). Together these confer a higher cardiovascular risk than each component alone.
Quality of Life
In addition to affecting life expectancy, obesity also reduces quality of life, even in the absence of comorbid diseases (13,14). This is most evident in physical functioning, including activities of daily living, and bodily pain domains. Furthermore, it appears that the morbidly obese and those with predominantly central obesity tend to have the lowest health-related quality-of-life scores.
There are other personal effects of obesity. In the United States and other westernized countries, obese persons experience discrimination that can affect employment opportunities, college acceptance, job earnings, rental availability, and marriage (12). Several studies show that physicians and medical students also harbor negative attitudes toward obese patients, which the patients themselves can sense, and which may negatively affect care.
Health Care Use and Costs
Along with the increased prevalence of obesity, health care use has increased for this disease. In the 1990s, physician visits related to obesity in the United States increased approximately 90% (15). Obese persons, on average, have more physician visits, receive more medical services, and fill more prescriptions than their nonobese counterparts. Given the medical consequences, obesity is also costly to society both directly, in terms of health care dollars, and indirectly, in terms of lost productivity and disability. Although the total economic costs of obesity are difficult to calculate, estimates for the direct health care costs have increased to $78.5 billion per year in the United States, accounting for 9.1% of the overall national health expenditure (3). There is little doubt that patients and society would benefit significantly if obesity were prevented or more successfully treated.
Evaluation
Despite the known consequences of obesity, both the medical community and society have been reluctant to consider it a disease and to recommend routine screening and treatment. Recently, however, a number of prominent medical organizations, including the U.S. Preventive Services Task Force, the American Medical Association (AMA), the American Association of Family Practice (AAFP), the American Diabetes Association (ADA), and the American Heart Association (AHA) have recommended that all adults be screened for obesity using the body mass index (BMI) and that they be appropriately treated (16, 17, 18, 19).
Degree and Distribution of Obesity
Calculating BMI
The first step in assessing obesity is to estimate body fat by calculating the BMI. Other methods, such as bioelectrical impedance, hydrodensitometry, dual-energy x-ray absorptiometry (DEXA), and computerized tomography (CT) scans, are more accurate but are expensive and are impractical in the office setting.
BMI is calculated by dividing weight (in kilograms) by height squared (in meters): BMI = Weight (kg)/Height squared (m2). If pounds and inches are used, the formula is as follows: BMI = (Weight [lb] × 703)/Height squared (in2). For ease of assessment, there are reference tables available, Internet-based online calculators, and programs that can be downloaded into a Personal Data Assistant (PDA), such as from the website of the National Institutes of Health (NIH; http://www.nhlbi.nih.gov/guidelines/obesity/ob_home.htm). Table 83.2 is an abbreviated BMI table as an example.
Classifying Weight Status by BMI
Based on the risks of mortality, diabetes, hypertension, and atherosclerotic coronary heart disease associated with different BMIs, the NIH and the World Health Organization (WHO) have developed a classification for weight based on BMI (12,20), which is shown in Table 83.3. A BMI ≥30 kg/m2 is classified as obese, which is further broken down into three subgroups of severity. The term morbidly
P.1426
obese generally refers to a BMI ≥40 kg/m2, and superobese refers to a BMI ≥50 kg/m2. Although currently the classification is the same for all racial/ethnic groups, it has been proposed that a healthy BMI for people of Asian descent is <23 kg/m2 and that ≥27 kg/m2 should be considered obese in this population, based on their risk of morbidity.
|
TABLE 83.2 Body Mass Index Table |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
TABLE 83.3 Classification of Weight Based on BMI |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
Although an increased BMI usually indicates increased body fat in the average person, there are circumstances where this is not the case, such as a professional athlete (who has increased muscle mass) or someone with anasarca (who has increased body fluid). Although such individuals have an elevated BMI, they should not be considered obese.
Measuring Waist Circumference
In addition to the degree of obesity, the distribution of body fat is also associated with the risk of complications from obesity. Individuals with more abdominal fat have a greater risk of comorbid conditions (such as diabetes) and mortality (21,22). Abdominal fat can be estimated using the waist circumference. In individuals with a BMI of 25 to 35 kg/m2, a waist circumference >40 inches (102 cm) in men, or >35 inches (88 cm) in women, portends a higher risk. In individuals with a BMI >35 or 40 kg/m2, the waist circumference adds little information.
Waist circumference can be measured by placing the tape measure just above the iliac crest in a horizontal plane around the abdomen. The tape should be snug and parallel to the ground, but should not compress the skin. The measurement should be taken at the end of normal respiration.
Another measure of fat distribution is the waist-to-hip ratio. This is calculated by dividing the waist circumference by the hip circumference. The hip circumference is measured similarly to the waist circumference described above, but at the widest part of the hips. A waist-to-hip ratio >1.0 in men or >0.8 in women is associated with higher risk. Either the waist circumference or the waist-to-hip ratio can be used; however, the waist circumference alone provides sufficient information and takes less time to do.
Risk Assessment
Once an individual's BMI and waist circumference have been determined, assessment should turn to whether there is any impact of the weight on other disease states, and whether there are other risk factors for cardiovascular disease. These can be divided into three categories (Table 83.4). The first category comprises diseases associated with a high risk of morbidity and mortality such as existing coronary artery disease. The second category comprises the other standard cardiovascular risk factors such as smoking and hypertension. The third category includes other obesity-associated diseases, such as osteoarthritis and stress urinary incontinence, which may be most important to the patient in terms of daily function and quality of life.
|
TABLE 83.4 Categories of Risk in Obese Patients |
||
|
Putting the entire assessment together, the overall risk associated with obesity can be estimated using the weight classification (or BMI) and the comorbid conditions (Table 83.5). The overall risk will help to determine whether a person needs to be treated, and if so, how aggressively. This is addressed further in the Management section of this chapter.
Assessment of Motivation and Readiness
Because treatment of obesity involves behavioral changes and thus significant patient commitment, the final step in assessment is to determine the patient's current motivation and readiness to lose weight. Reviewing several questions with the patient can help the practitioner decide whether
P.1427
to counsel the patient to start a weight-loss program now or defer it to another time (Table 83.6).
|
TABLE 83.5 Estimation of Risk for Obese Patientsa |
||||||||||||||||||||||||||||||
|
||||||||||||||||||||||||||||||
Whether it is the patient's idea to lose weight or someone else's (family, significant other) affects patient motivation. If the practitioner is the one who raises the issue, then it is helpful to discover whether or not the patient has thought about this, and whether or not the patient thinks losing weight is a good idea. Only if the patient recognizes the importance of weight loss are the efforts likely to be successful.
Understanding what prompted the person to seek help at this time can help the physician understand the underlying motivation and goals. These can be used to reinforce the importance of weight loss, not just for the patient's reasons, but also for appropriate medical reasons. Even if the patient did not seek help for obesity, personalizing the message about weight loss is important. It links the patient's current symptoms, health status, and risk of developing diseases to the benefits they can anticipate by losing even small amounts of weight.
Assessment of stress level and mood can help the physician decide if this is an appropriate time to start a weight-loss program. Although the physician should not postpone treatment indefinitely, it is important to keep in mind that losing weight requires time and effort, so the patient must be able to commit that or the patient will be less successful.
|
TABLE 83.6 Questions to Ask to Assess Patient Readiness and Motivation to Start a Weight-Loss Program |
|
|
It is reasonable to assess patients for binge-eating disorder (see Etiology, above). Successful weight loss may be better achieved in combination with or after therapy for this eating disorder. Additionally, a good understanding of the requirements of weight-loss treatment by the patient, and a belief that he or she can make the needed changes (good self-efficacy), will increase the likelihood of success.
A careful exploration of how much the patient wants to lose and in what time frame will help to identify any unrealistic goals in these areas (e.g., trying to lose 30 lb in 2 to 3 months). The physician can then provide feedback on how much weight loss is important for medical reasons (which is often less than the patient desires), and over what time frame (e.g., 1 to 2 lb per week is considered to be the safe and effective rate). Exploring the reasonableness of the weight loss goals and the time frame is essential to setting appropriate short-term goals.
Finally, it is useful to assess the resources (e.g., financial, social, time) available to the patient. The reasonableness and achievability of a patient's goals, as well as the specific approaches to these goals, are often dependent on the resources available to the patient.
The answers to these and similar questions can help determine whether the patient is ready to make the changes needed to lose weight. It is useful, in this regard, to employ a “Stages of Change” Model (23), as in Chapter 4. Depending on the patient's stage, different approaches can be used to get the patient into the action or maintenance stage. For instance, if an obese person is in the precontemplation stage, then the most effective and efficient use of time may be to deliver a concise message about the specific importance of weight loss for the patient and some information for the patient to review. This approach, when followed up over time (or a series of visits), can eventually result in a patient who is ready to lose weight (i.e., is in the action stage) and will reduce the practitioner's frustration related to counseling someone who is not ready to make changes. Furthermore, if weight loss is medically indicated but not discussed, the patient may infer it is not important. Thus a brief discussion about weight management is indicated
P.1428
for every patient and is discussed further in the Prevention section.
|
TABLE 83.7 Ten Key Steps in Weight Management in the Primary Care Setting |
|
|
Management
General Approach
Weight management should be approached within the context of a working partnership between the practitioner and patient that takes into account the patient's attitudes and beliefs about weight and weight-loss treatments. More frequent contact during the weight-loss efforts can enhance compliance and produce better results. Such contact need not be limited to office visits with the practitioner, but could include weight checks with a nurse, as well as phone calls or e-mails from physicians or other office personnel. After the initial assessment, the practitioner can turn to weight-loss strategies. Table 83.7 outlines the key steps for weight management in the primary care setting.
The most effective approach to weight loss is a combination of calorie reduction, physical activity, and behavior modification (12,24). These can be added over a series of visits. In addition, similar to the approach to hypercholesterolemia, caregivers should use a stepped approach based on the patient's overall risk (Table 83.8). For instance, in a patient at high risk for complications, the first step should be a trial of caloric reduction, physical activity, and behavior change. These efforts can be intensified over a number of months (6 to 12 months depending on risks). If unsuccessful, pharmacotherapy should be considered. Finally, depending on patient risk, bariatric surgery should be considered.
|
TABLE 83.8 Stepped Obesity Management Recommendations Based on Patient Health Riska |
||||||||||||||||||
|
||||||||||||||||||
Patients should be counseled to avoid programs or approaches that are highly restrictive, such as very-low-calorie diets with an intake of <800 kcal per day, or those that exclude or overemphasize entire groups of foods or nutrients. Weight loss can generally be achieved using a balanced diet, and nutritional supplements are not required. Recent public health guidelines nevertheless recommend that adults consider taking one multivitamin per day (25). Even in the absence of weight loss, a balanced diet with fresh fruits, fresh vegetables, low-fat dairy products, chicken and fish (such as the DASH [Dietary Approaches to Stop Hypertension] diet) can significantly impact indices of health such as blood pressure (26).
Weight-Loss Goals
Very few obese patients lose enough weight to be reclassified as “normal.” At the same time, a 5% to 10% reduction in weight is achievable and can have a significant impact on comorbidities such as diabetes and blood pressure (27,28). Furthermore, a weight loss of this magnitude also reduces the risk of developing diabetes in people who are at high risk by 50% (29, 30, 31). With that in mind, the initial goal should be to lose 10% of current body weight over a 6-month period.
Rate of Weight Loss
Patients can typically lose 0.5 to 1 lb a week by reducing their caloric intake by 300 to 500 kcal per day (1 lb = 3,500
P.1429
calories). A reduction in caloric intake by 500 to 1,000 kcal per day can result in the loss of 1 to 2 lb per week. These levels of caloric consumption and rates of weight loss are considered safe without any special monitoring, and faster initial weight loss does not produce better results in the long run (i.e., at 1 year) (32). If the initial caloric reduction does not produce the desired results, calories can be further reduced to about 1,000 kcal per day. Amounts below this require special monitoring.
It is common for weight loss to plateau after 6 months. That should be discussed with patients up front; patients should be reassured that plateauing is normal. If further weight reduction is desired eventually, options include taking a respite of several months (i.e., maintaining weight but not attempting to lose more weight), trying methods that previously worked again, and trying methods they have not previously employed.
Diet
The cornerstone of weight loss is creating a caloric deficit—that is, taking in fewer calories than the number of calories being spent. For most people, this requires a reduction in caloric intake, with or without an increase in expenditure, rather than an increase in caloric expenditure alone. For those with BMIs ranging from 25 to 35 kg/m2 a reduction in daily caloric intake by 300 to 500 kcal per day is recommended to produce weight loss of 0.5 to 1 lb per week. For men this usually means consuming 1,600 to 1,800 kcal per day, and for women, 1,400 to 1,600 kcal per day. For those with a BMI >35 kg/m2, reduction in caloric intake by 500 to 1,000 kcal per day is recommended for a weight loss of 1 to 2 lb per week. For men this usually means limiting calories to 1,200 to 1,600 kcal per day, and for women 1,000 to 1,200 kcal per day. Table 83.9 summarizes these recommendations.
Practical suggestions on food shopping and preparation, low-calorie menus, and dining out are available from numerous resources, including the Practical Guidelines from the NIH (available at http://www.nhlbi.nih.gov/guidelines/obesity/ob_home.htm) (33). For all diet plans, weight regain can occur when the diet is stopped.
Specific Dietary Recommendations
The optimal dietary recommendations for healthy adults are uncertain. The U.S. Department of Agriculture released a revised Food Guide Pyramid in 2005. It recommends a balanced diet that emphasizes grains, fruits, and vegetables, and limits total fat to <30%, saturated fat to <10%, and minimizes sweets (see Chapter 15, Fig. 15.1). The revised Food Guide Pyramid also places greater emphasis on the importance of whole grains that are high in fiber and micronutrients and have less impact on blood sugar (e.g., oatmeal, whole wheat bread, brown rice) (34,35). Consumption of trans fats (e.g., margarine and partially hydrogenated oils found in many packaged foods) have greater negative health consequences than saturated fats and should be kept to a minimum (36, 37, 38, 39). Finally, the Food Guide Pyramid encourages consumption of lean proteins, including fish, beans, peas, and nuts, as alternatives for meats.
|
TABLE 83.9 Recommended Initial Caloric Reduction Based on Baseline BMI |
||||||||||||
|
The “Low Carb” Frenzy
Several proponents of their own diets have argued that diets that emphasize protein intake, minimize carbohydrates, and may or may not ignore fat are more effective at weight reduction than other types of diets. For example, the Atkins diet emphasizes consumption of protein, severe reduction in carbohydrate intake (<20 g per day initially), and pays little attention to fat intake, often resulting in consumption of high-fat foods. Other variations on this theme include the South Beach Diet and the Zone Diet.
Although initially there were few data on the outcomes of low-carbohydrate diets, the results of several controlled clinical trials showed significantly greater weight loss at 6 months in the low-carbohydrate groups compared with the low-fat groups (40, 41, 42, 43, 44). However, after 1 year, there was no significant difference in weight loss between the two groups. The low-carbohydrate diets also increased high-density lipoprotein (HDL) and markedly decreased fasting triglyceride concentrations. Although high dropout rates were seen in all groups, there tended to be fewer dropouts in the low-carbohydrate groups, which may indicate patients are more likely to adhere to this type of diet.
Some studies of low carbohydrate and other very restrictive diets have excluded people with “serious or significant” medical conditions, although people with hypertension, diabetes, and/or the metabolic syndrome have sometimes been included. Thus caution should be used in the face of certain diseases. For example, because the initial weight loss from low-carbohydrate diets is a result
P.1430
of diuresis, persons who are at risk for dehydration should either be discouraged from using the Atkins diet or should be monitored closely.
Finally, it is important to keep in mind that the weight loss from “low-carb” diets is achieved through a reduction in calories eaten, rather than some “magic” with intake of fewer carbohydrates. Just as with any diet plan, a reduction in caloric intake by 500 to 1,000 kcal per day generally results in a weight loss of 1 to 2 lb per week. Overall, the most effective diet is the diet that the patient can “stick with” over time. The decision on which diet to use should be made with the patient's preferences and medical conditions in mind.
Meal Replacements
Another approach to dieting is using meal replacements, such as Slim-Fast, which are widely available to the public. Generally these are used as partial meal replacement (PMR) plans, wherein two meals each day are replaced, and a third is consumed as a balanced low-calorie meal.
Although data are somewhat limited, several trials indicate that PMR plans result in an average 5.5- to 6.6-lb greater weight loss at 3 months and a 5.3- to 7.5-lb greater weight loss at 1 year compared with standard low-calorie diets (45). These also appear to be safe in patients with comorbid conditions including diabetes, and compliance with this approach may be greater for longer time periods. Thus the use of PMR plans should be considered, especially for patients for whom an easy, less-time-consuming way of achieving a low-calorie diet is desirable.
Medically Supervised Programs
Another option for patients is enrolling in a medically supervised program. These generally employ the use of very-low-calorie diets (VLCDs; <800 kcal per day) through the use of liquid supplements (Medifast or Optifast) or other prepackaged meals. Early use of VLCDs was associated with some deaths, with the cause thought to be attributable to a lack of high-quality protein. This was rectified with a change in the formulation of the supplements used and the focus on protein-sparing modified fasts.
Overall, limited available data suggest that the VLCDs used in medically supervised programs may result in faster initial weight loss, but probably do not result in greater long-term (1 year) weight loss (46). Such severe dietary restriction is also associated with more side effects, ranging from dry mouth and constipation to orthostasis, fatigue, hair loss, to increased rates of cholecystitis, which might lower compliance rates over the long-term.
Referral to supervised weight-loss programs that employ VLCDs may be indicated in highly motivated patients interested in faster weight loss. However, these tend to require substantial time commitments (e.g., weekly visits), are often quite costly, and, as with all weight-loss programs, are rarely covered by insurance.
Registered Dieticians
The resources and help of dieticians should not be overlooked. These trained professionals can provide one-on-one counseling that, typically, is based on a balanced, low-calorie diet. As the main focus of their counseling is the diet, the dieticians can spend the extra time needed to explain concepts such as calories and ways to reduce them, different nutrients and their sources, and how to read food labels. They can also develop detailed individual diet plans and provide followup visits to assess compliance and problem solve to overcome barriers. These services are especially useful for the “novice” dieter who knows little about diet and nutrition. Insurance coverage for dietician services varies by type of insurance, state, and presence of other comorbidities. Even without coverage, dietician services are often as affordable as commercial programs and should be considered a useful adjunct.
Community-Based Weight-Loss Programs
There are a variety of commercial weight-loss programs (e.g., Weight Watchers, Jenny Craig) available to patients, including a number of online programs. These typically provide social support and frequent followup, specific dietary information, and information to help identify problematic behaviors and situations and develop different ways to respond. In the face of very little evidence available from randomized controlled trials, these programs (in particular, Weight Watchers) may improve weight loss for periods up to 2 years (47).
Commercial weight-loss programs may be indicated in some patients and can be discussed as an adjunct to their ongoing efforts. However, it is important to keep in mind that not all programs are the same and some may be expensive, ineffective, or even dangerous. Because commercial weight-loss programs change frequently to keep up with consumer demand, it is difficult to provide specific recommendations on programs. Historically, programs such as Weight Watchers (http://www.weightwatchers.com) and Jenny Craig (http://www.jennycraig.com) have been developed by registered dieticians and have included physicians and psychologists on their boards. There are also support groups, such as “Take Off Pounds Sensibly” (TOPS, http://www.tops.org) or Overeaters Anonymous (OA, http://www.oa.org), which do not offer specific diet information, but simply provide a setting for regular group support and interaction. Other things to consider when helping a patient choose a program are whether the program emphasizes a slow, steady weight loss and includes a program for weight maintenance. Finally, a program should provide detailed information about fees and costs of any additional items (24).
P.1431
Physical Activity
Regular physical activity is essential to long-term weight control. It can help modestly with initial weight loss, but more importantly, it is the best predictor of weight-loss maintenance (48). Even in the absence of weight loss, increased physical activity or exercise is associated with redistribution of adiposity away from the abdomen and reduced morbidity and mortality. It is recommended that caregivers regularly monitor and recommend routine physical activity to all patients.
In designing a physical activity plan with a patient, it is important to set appropriate and achievable goals. Setting inappropriately ambitious physical activity goals are likely to result in abandonment of the exercise program (49). In addition, several studies have compared the impact of lifestyle activity (e.g., taking the stairs, parking further away) versus aerobic exercise and demonstrated that they result in similar health benefits (50,51).
As with other behavioral interventions, the physical activity plan should be tailored to the individual. Although some may choose to engage in vigorous physical activity, others should be encouraged to start with low-impact, moderate-intensity physical activity (e.g., walking) of short duration, with a goal of accumulating 30 minutes of physical activity or more on most days of the week. After this goal is met, the practitioner can discuss with the patient if a further increase in activity is realistic. Evidence suggests that physical activity for 60 minutes each day imparts increased benefits and is more likely to help maintain weight loss (52); however, this level of physical activity may be hard to achieve and maintain. Thus, patients should be provided with advice that is realistic and manageable for them.
Whatever plan of physical activity is chosen, it should have the following SMART characteristics: it is Specific (e.g., walking, swimming),Measurable (e.g., duration and or distance), Action-oriented (cardiovascular, not weight training or abdominal exercises), Realistic, andTimely (start with short-term goals that build in intensity and duration). The following is an example of a SMART goal that a practitioner and patient may negotiate: “I will walk briskly for 20 minutes on Monday, Wednesday, and Friday mornings this coming week. After I reach this goal, I will reward myself by purchasing a new CD. For the following 5 weeks, I will increase my time by 5 minutes per day each week, until I am walking 45 minutes every Monday, Wednesday, and Friday.” A followup visit after 6 weeks can assess progress and establish new goals.
Behavior Modification
Behavior modification encompasses a variety of techniques to help people change their behaviors and can be tailored to help achieve weight loss (Table 83.10). Research shows that the most important behavior change tool for the majority of people is self-monitoring through the use of a food log. Self-monitoring is essential to the process of behavior change. Food and activity logs are frequently the behavioral activities that patients are most resistant to do; the willingness to do them also seems to reflect a readiness to “do what it takes” to change one's lifestyle. In addition, the act of self-monitoring alone may cause people to eat less and/or exercise more.
|
TABLE 83.10 Examples of Behavior Modification Strategies That May be Useful in Weight Reduction |
||||||||||||||
|
In addition to self-monitoring, there are a number of other strategies to control portions and reduce caloric intake. Stimulus controlidentifies triggers or cues that may encourage unplanned eating and attempts to remove them (53). Meal planning can also play a major role in controlling portions and avoiding overeating. These efforts are likely to reinforce dietary adherence by increasing access to appropriate foods and reducing impulsive intake of calorically dense foods.
Relapse prevention is another important behavioral strategy for weight control. Patients are encouraged to identify and limit their exposure to high-risk situations and plan accordingly in an effort to minimize overeating or unplanned eating episodes. Finding ways to overcome predictable dietary or physical activity slips and “get back with the program” is also a key component of relapse prevention. Use of a reward system may also enhance compliance with behavior changes. A final behavior modification tool is to seek positive social support. For some this can be found in weight-loss groups or can be among friends who may all be trying to lose or maintain their weight actively.
P.1432
During each office visit the patient and physician can review the weight-loss goals, adherence to the diet and physical activity plans, and any barrier limiting success, and they can problem solve together, identifying behavioral tools that might enhance weight-loss efforts.
Pharmacotherapy
If, after at least 6 months, a regimen of a low-calorie diet, increased physical activity, and behavior modification fails to induce significant weight loss, pharmacotherapy can be considered. Appropriate candidates for pharmacotherapy are patients with (a) a BMI ≥30 kg/m2 or (b) a BMI of 27 to 29.9 kg/m2 with comorbid conditions (Table 83.8) (12).
Pharmacotherapies can be divided into those that are FDA approved for weight loss (Table 83.11), those that are FDA approved for other indications that also can induce weight loss, and over-the-counter agents promoted for weight loss. No matter which agent is used, weight is often regained after cessation of medication. Medication should only be included along with lifestyle changes as part of a comprehensive weight-loss plan. In addition, the potential side effects and the need to continue drug therapy to maintain weight loss should be discussed with the patient prior to starting medication.
|
TABLE 83.11 FDA-Approved Weight-Loss Medications |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
FDA-Approved Drugs for Weight Loss
FDA-approved medications for weight loss can be broadly divided into long-term and short-term agents (Table 83.11). Orlistat (Xenical) reduces dietary fat absorption by approximately 30% and produces an average weight loss of 2.6 kg (5.7 lb) at 6 months and 2.9 kg (6.4 lb) at 1 year when compared with placebo (54). When continued for 2 years, orlistat lessens regain of weight and improves weight-loss maintenance (55). Treatment with orlistat also results in significant decreases in systolic blood pressure, waist circumference, total cholesterol, low-density lipoprotein (LDL) cholesterol, and fasting serum insulin and glucose levels. Orlistat has little systemic absorption, so its side effects are mainly gastrointestinal and include flatus with discharge, steatorrhea, diarrhea, fecal urgency, and incontinence. Reduction of fat intake and the use of psyllium (as found in Metamucil) can decrease these side effects; in
P.1433
contrast, a high-fat meal after taking orlistat can exacerbate them. Finally, there is the potential for malabsorption of the fat-soluble vitamins (A, D, E, and K), so multivitamin supplementation between meals is recommended, as is careful monitoring of prothrombin time (PT)/international normalized ratio (INR) for patients taking warfarin (see Chapter 57). Orlistat is taken 120 mg by mouth 30 minutes before each meal.
Sibutramine (Meridia) is a serotonin and norepinephrine reuptake inhibitor that acts to enhance satiety. Sibutramine results in an average weight loss of 4.5 kg (9.9 lb) when compared with placebo at 1 year (54). Use of sibutramine has resulted in improvement in blood glucose concentration, but no consistent effect on lipid levels. The effect on blood pressure may vary, but some studies show an increase in diastolic blood pressure when compared to placebo, and a slight increase in average heart rate (~4 beats/min). Pre-existing hypertension is not an absolute contraindication to the use of sibutramine, but blood pressure should be well-controlled before and during administration of the drug (56). Valvulopathy and pulmonary hypertension have not been seen with sibutramine. Sibutramine is taken orally 10 mg/day.
A number of other prescription medications for weight loss, such as phentermine and diethylpropion, are FDA approved for short-term use, which is defined as less than 12 weeks. On average, phentermine results in 3.6-kg (7.9-lb) greater weight loss than placebo, and diethylpropion results in a 3.0-kg (6.6-lb) greater loss (54). There are some reported cases of pulmonary hypertension and valvulopathies, as well as stroke (phentermine), associated with these drugs after long-term use. Both are thought to work by inhibiting appetite, although there may be separate effects on metabolism or the central nervous system. Similar to amphetamines, these drugs can cause palpitations, tachycardia, increased blood pressure, and tachyphylaxis and tolerance over time. They should be taken in the morning to lessen any sleep disturbance. Several of the short-term agents (benzphetamine and phendimetrazine) have limited potential for abuse and are class IV controlled substances. Several promising new pharmacotherapies for obesity are in testing, including a cannabinoid-1 receptor blocker, rimonabant (57), and a genetically engineered recombinant human variant ciliary neurotrophic factor (rhvCNTF) that signals through leptinlike pathways (58). Clinicians will likely hear more about such approaches in the future.
FDA-Approved Drugs for Other Indications that Can Cause Weight Loss
Several drugs have demonstrated some efficacy for weight loss, but are FDA approved for other indications and not for weight loss. These include metformin, fluoxetine, sertraline, bupropion, topiramate, and zonisamide. It is not appropriate to prescribe these medications primarily for their ability to produce weight loss. However, in patients who have other treatment indications, such as diabetes, it is appropriate and important to consider whether any of the medication options could enhance or promote weight loss (e.g., metformin).
Over-the-Counter Weight-Loss Products
Two over-the-counter agents, phenylpropanolamine (e.g., Acutrim, Dexatrim) and ephedra or ma huang (e.g., Metabolife), have been taken off the market because of concerns of adverse cardiovascular effects (increased risk of stroke). Sale of ephedra-containing products was prohibited by the FDA in April 2004. Because of such safety concerns and limited quality control over dietary supplements, use of over-the-counter products for weight loss should not be recommended.
Bariatric Surgery
If pharmacotherapy is not tolerated or does not achieve the desired weight reduction in combination with diet, physical activity, and behavior modification, bariatric surgery should be considered. Appropriate candidates for weight loss surgery include patients with (a) a BMI ≥40 kg/m2 or (b) a BMI of 35 to 39.9 kg/m2 with other high-risk comorbid conditions or weight-induced physical problems interfering with performance of daily activities (Table 83.8) (12,59). A discussion of surgical options should include the long-term side effects, such as the possible need for reoperation, gall bladder disease, and malabsorption.
Surgical procedures commonly used today can be classified as predominantly restrictive (vertical-banded gastroplasty, adjustable gastric banding) or malabsorptive (Roux-en-Y gastric bypass, biliopancreatic diversion with duodenal switch), as shown in Figures 83.1 and 83.2. In general, gastric bypass appears to produce more weight loss than gastroplasty, and laparoscopic surgeries tend to have fewer wound complications (e.g., infections).
Numerous case series show marked improvement in most obesity-related comorbidities, including type 2 diabetes (up to 90% resolve), hypertension (up to 66% resolve), and sleep apnea, as well as improvements in lipids, left ventricular wall thickness, mobility, return of fertility, and significant improvement in quality of life. Many patients can be off medications for obesity-related comorbidities 3 years after surgery (60,61). Bariatric surgery has resulted in weight losses between 22 and 37 kg (48 and 81 lb) greater than nonsurgical treatments, which may be maintained for more than 8 years (62).
The risks of bariatric surgery include death, which is reported to be <1% in selected patients, and <2% in
P.1434
studies of administrative data (i.e., unselected patients). Overall rates of complications vary according to the procedure, ranging from 7% to 38% for gastrointestinal symptoms, 3% to 17% for nutrition and electrolyte imbalances, and 2% to 12% for complications requiring reoperation (e.g., stenoses, bleeding). Complication rates are lower in high-volume (>100 procedures per year) centers. Recently, a program to designate Centers of Excellence in Bariatric Surgery was established, which should eventually help providers and patients make informed choices when choosing this option. Finally, as with most surgical referrals, information about the individual surgeon's practice, weight-loss results, and complication rate should be sought prior to making a referral.
|
FIGURE 83.1. Bariatric procedures that work predominantly through malabsorption are (A) jejunoileal bypass, (B) biliopancreatic diversion, and (C) duodenal switch. (From Mun EC, Blackburn GL, Matthews JB. Current status of medical and surgical therapy for obesity. Gastroenterology 2001;120:674 , with permission.) |
|
FIGURE 83.2. Bariatric procedures that work predominantly though restriction of food intake are (A) vertical-banded gastroplasty, (B)adjustable gastric banding, and a combination of restriction and malabsorption (C) Roux-en-Y gastric bypass. (From Mun EC, Blackburn GL, Matthews JB. Current status of medical and surgical therapy for obesity. Gastroenterology 2001;120:674 , with permission.) |
Relapse
For most people it is difficult to maintain the lifestyle changes they adopted to achieve weight loss and they face weight regain over the long-term. Efforts to prevent relapse, including informing patients of potential weight regain with the cessation of efforts, are important. Monitoring the patient's weight in the office may also be helpful. Weight regain can be approached in a similar way to a weight-loss plateau—that is, restarting methods that previously worked again or trying methods not previously employed. Motivation frequently wanes over the long-term, so efforts to increase motivation may be needed (e.g., a new reward system) along with increased social support.
P.1435
Prevention
Overweight and obesity are among the top 10 health priorities established by the U.S. Department of Health and Human Services in Healthy People 2010. Given the difficulty of successfully treating obesity, prevention is of paramount importance. Ideally, prevention should begin in childhood and continue through adulthood. Many medical encounters also provide an opportunity for prevention.
Public Health Interventions
Efforts to prevent obesity may be most effective if implemented at the public health level. Like efforts to reduce smoking, efforts to reduce obesity should combine multiple strategies. Information about healthy lifestyles should be taught throughout elementary and high school education, and should continue as much as possible throughout adulthood. Information about foods should be made more available at points of access such as restaurants. Inclusion of portion size and nutrient and calorie information in menus (as is done in some other countries) would help consumers make informed choices.
Access to healthy and affordable foods should be assured for everyone. Furthermore, access to and marketing for unhealthy foods can be limited or eliminated in schools, on billboards, and in media targeted at children (such as cartoons on TV, or kid's magazines). In recent years, policy changes at elementary, middle, and high school levels have attempted to limit access to unhealthy foods at school. Grass-roots movements that encourage people to patronize and support restaurants that offer healthy choices and reasonably sized portions could also make a difference.
To increase physical activity, schools could once again require physical education and include time for active play, especially for young students. City planning could include sidewalks to allow for walking, as well as public parks and recreation sites to encourage regular physical activity. Finally, health policy changes that reimburse for obesity prevention and treatment prior to the onset of significant comorbidities would lessen the burden of obesity on the public. Providers can play a role in effecting such changes at local, state, and national levels, and can encourage their patients to do the same.
Primary Care Interventions
In the practitioner's office, prevention can be approached very simply, by measuring height and weight and calculating BMI on all patients and tracking these over time. One or two statements about the patient's weight status each visit (or at annual prevention-oriented visits) can be used. For the patient whose weight is normal, this could include congratulations on having (and maintaining) a normal weight and encouragement to continue. For an overweight patient or a patient who has recently gained some weight, the practitioner should consider a statement that indicates this fact or pattern, and encourages the patient not to gain further weight. In an obese patient, when obesity-related comorbid conditions are diagnosed or suspected, their relation to weight or weight gain can be explained to the patient. Finally, information about BMI, healthy weight, and weight loss can be displayed and/or provided to patients.
Specific References*
For annotated General References and resources related to this chapter, visit http://www.hopkinsbayview.org/PAMreferences.
P.1436