Obesity Management1
Lawrence J. Cheskin
Kavita H. Poddar
1Abbreviations: ACSM, American College of Sports Medicine; BMI, body mass index; BMR, basal metabolic rate; FDA, Food and Drug Administration; FFQ, food frequency questionnaire; LCD, low-calorie diet; METs, metabolic equivalents; NHLBI, National Heart, Lung, and Blood Institute; VLCD, very-low-calorie diet.
The prevalence of obesity has nearly doubled in the past generation, with two thirds of US adults now being overweight or obese. If current trends continue, investigators have projected that essentially the entire US population will be overweight by 2030 (1). The increase in prevalence is even more dramatic among children and the extremely obese (2). Obesity has truly reached epidemic proportions, undoubtedly as a result of unfavorable shifts in diet and exercise habits of the US population (3). Even developing nations are seeing an increase in obesity, with the projected number of obese estimated in billions by 2030 (4), in large part related to adoption of Western diet and exercise patterns (5).
What is causing this epidemic? Despite discoveries in the molecular genetics of obesity, a major role for genetic influences is not a likely explanation for the rapid changes in the prevalence of obesity. Obesity is a result of a complex interplay among genetic, behavioral, and environmental factors that include diet and exercise.
In the United States, although the percentage of energy intake derived from fat is decreasing (from a high of 40% to ˜32% today), total daily caloric intake is increasing, and refined carbohydrate intake has increased (6). Whereas increasing numbers of adults and children engage in virtually no physical activity (7), the environment is a large contributor to this inactivity and thus to the epidemic of obesity in the United States (8).
Obesity is a close second to cigarette smoking as the most important modifiable cause of death. It is a risk factor for diseases of virtually every organ system, including certain cancers, and is the most important risk factor in the development of diabetes and other health complications (9). The risk of complicating medical conditions increases with the degree of obesity (9), although for some complications—notably dyslipidemias, which are associated with cardiovascular risk factors, type 2 diabetes, and hypertension—the risk correlates best with the regional distribution of fat (10). Central (visceral) deposition of fat (the “apple-shape” pattern), seen more commonly in men, increases risk, whereas excess fat in the lower body (thighs, hips and buttocks), seen more commonly in women (the “pear-shape” pattern), is associated with a lesser risk of such complicating conditions.
Obesity increases overall mortality and shortens life expectancy by at least several years in individuals with body mass index (BMI) greater than 25 kg/m2; this reduction can be dramatic for those who have a BMI greater than 35 kg/m2 (11). In addition to the medical risks—and often more motivating for many people seeking to lose weight—are the untoward psychosocial consequences of obesity (12, 13, 14). Prejudice against obese individuals is widespread. The resulting social effects and job
discrimination contribute to low self-esteem and depression among obese people who seek treatment. Notable also are the greater social stigma borne by obese women compared with obese men in the United States and the higher prevalence of obesity among those of low socioeconomic status, African-Americans, Latinos, and Native Americans. For example, approximately 80% of middleaged African-American women in the United States are overweight or obese. Compelling evidence shows health benefits associated with even modest weight loss, a finding suggesting that people who are obese should be encouraged to lose weight (15, 16, 17, 18).
discrimination contribute to low self-esteem and depression among obese people who seek treatment. Notable also are the greater social stigma borne by obese women compared with obese men in the United States and the higher prevalence of obesity among those of low socioeconomic status, African-Americans, Latinos, and Native Americans. For example, approximately 80% of middleaged African-American women in the United States are overweight or obese. Compelling evidence shows health benefits associated with even modest weight loss, a finding suggesting that people who are obese should be encouraged to lose weight (15, 16, 17, 18).
This chapter aims to provide an overview of the assessment and treatment of obesity, with the primary focus on dietary and exercise interventions. Pharmacologic and surgical therapies are a second-line option in the treatment of obesity and are reviewed in less depth.
EVALUATING OBESITY
Physical Assessment
Classification of obesity was proposed by an expert panel convened by the National Institute of Health, National Heart, Lung, and Blood Institute (NHLBI) in 1998 after extensive review of health complications associated with this condition (19). The panel classified obesity and overweight status based on BMI and waist circumference. Associated disease risk is shown in Table 59.1 (20). Obesity is technically defined as an excess of body fat (>25% of body weight for men and >30% for women), rather than an excess of body weight in itself (19). However, the measurement of percentage of body fat is more difficult to obtain and is not as intuitive as body weight. Thus, relative weight is a reasonable surrogate measure for adiposity. Measuring weight adjusted for height, or BMI, defined as weight in kilograms divided by the square of the height in meters, is usually the first step in assessing obesity and is very useful for diagnosing and grading the severity of the condition and its attendant risks (see Table 59.1). Although BMI is the standard measure of relative weight, it may overstate the actual degree of adiposity in very muscular people (e.g., certain types of athletes and laborers), and it may understate adiposity in very sedentary individuals with little muscle mass. The latter is called sarcopenic obesity, characterized by a normal or low BMI with increased percentage of body fat and reduced lean body mass. A BMI of 25 to 30 kg/m2 is defined as overweight, 30 to 40 kg/m2 as obese, and 40 kg/m2 or higher as severely or morbidly/grade III obese (20).
Waist circumference is the second step in the assessment of obesity. A waist circumference larger than 88 cm (35 in) in women and larger than 102 cm (40 in) in men constitutes abdominal or visceral obesity and is associated with an increased risk of health complications (20). Waist circumference can be easily measured with a tape rule around the widest point above the hips. In the case of abdominal fat deposition, even mild excess adiposity may pose medical complications, such as increased risk of hypertension, dyslipidemias, and type 2 diabetes (10, 20, 21, 22). Visceral obesity can exist even in the absence of overall obesity (i.e., at BMIs below the cutoff points for obesity or overweight) (10, 20, 21, 22). With visceral obesity, even with a normal BMI, it is probably best to encourage weight loss for medical reasons, especially if the patient already suffers from complicating medical conditions or has a strong family history of diabetes, cardiovascular, or cerebrovascular disease. For patients with cosmetic or trivial obesity, the benefits (and motivators) for successful weight loss are more psychosocial than medical. These patients should be encouraged to focus on a healthier diet (with low refined carbohydrate, low saturated fat, and high fiber) and increased physical fitness rather than just the number on the scale.
Psychosocial and Behavioral Assessment
A psychosocial and behavioral assessment should be performed because it can provide considerable information about the patient’s readiness to lose weight as well as identify disordered eating behaviors. Obese individuals commonly exhibit depression, with the degree of severity often greater with severe obesity (23, 24, 25). A behavioral
psychologist or other skilled professional can inquire into depressive symptoms by asking about the patient’s mood and related symptoms and signs or assessing depression with formal tests (26). Obese persons with significant depression should be provided appropriate treatment (cognitive behavior therapy or pharmacotherapy) before or during weight reduction efforts.
psychologist or other skilled professional can inquire into depressive symptoms by asking about the patient’s mood and related symptoms and signs or assessing depression with formal tests (26). Obese persons with significant depression should be provided appropriate treatment (cognitive behavior therapy or pharmacotherapy) before or during weight reduction efforts.
TABLE 59.1 CLASSIFICATION OF OVERWEIGHT AND OBESITY BY BODY MASS INDEX, WAIST CIRCUMFERENCE, AND ASSOCIATED DISEASE RISK | |||||||||||||||||||||||||||||||||||||||||||||||||
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Approximately 30% of obese individuals who seek weight reduction suffer from binge eating disorder (27). Binge eating is characterized by consumption of large amounts of food until one is uncomfortably full and eating alone when not hungry. In addition, patients have a loss of control over eating behavior and a negative emotional state after the binge (27). Other clues to the presence of an eating disorder or binge eating disorder include altered body image (believing one is obese when one is not) and obsession with one’s body weight (recurring thoughts or weighing oneself multiple times daily). When purging (vomiting or using laxatives or diuretics) or compulsive exercise is used following binging to control weight, bulimia nervosa, rather than binge eating disorder, is the likely diagnosis. Although anorexia nervosa and bulimia nervosa are commonly recognized as serious eating disorders (28), binge eating disorder is more common and often occurs in those who are overweight or obese rather than underweight. Merely prescribing a diet is usually not helpful and may even be counterproductive in an obese patient suffering from this disorder. Referral to a specialized treatment program may be helpful. Specific cognitive behavioral therapies have been developed for the treatment of binge eating disorder (29); however, the condition often responds favorably to a structured, individualized weight loss program along with behavioral therapy. Behavioral evaluation also may identify situations, feelings, or other issues that lead to inappropriate eating (i.e., eating that is not triggered by hunger).
Evaluating Dietary and Activity Habits
A complete dietary and physical assessment is helpful in evaluating the contribution of these factors to weight gain in an obese individual (30). This assessment can identify problem areas related to diet and exercise that may need modification to lose weight. Formal methods of assessing diet intake including 24-hour recall, 7-day food records, food frequency questionnaires (FFQs), and structured interviews (31, 32, 33) can help to determine the obese person’s current food choices and eating habits. Moreover, general discussions such as talking about past dieting experiences (if applicable) and asking the reason the patient thinks that he or she was not successful in the past can help in learning more about the patient’s motivations, needs, and barriers to change.
It is important also to ask about current medications, including over-the-counter or prescription drugs, herbs, and vitamin or mineral supplements if any. This information can help assess for potential food-drug interactions, assess daily intake in relation to nutrient requirements, and assist in the evaluation of methods used to address weight and nutritional issues by the patient. Often, an obese person reveals more information to a dietitian when specifically probed to answer these questions than when meeting with a primary health care provider. Any food allergies or intolerances (e.g., gluten, lactose) also should be covered.
Different dietary assessment methods have their strengths and limitations. For example, a 24-hour diet recall is helpful in assessing food and beverage intake, including the type and amount of food, brand names of foods, cooking methods, time of day, and location of eating (31, 32, 33). Multiple-day food records or food diaries assess food and beverage consumption over a period of typically 3 to 7 days, and intake is recorded either before or after eating. It is helpful for both the patient and the clinician to discuss how to measure or estimate food portions appropriately to create accurate accounts of food consumed and to document as many aspects of the food as possible (e.g., method of food preparation, type and amount of condiments used, name brands, restaurant names). Behaviorally relevant information also can be recorded in multiple-day food diaries, including an assessment of hunger levels before and after eating, in addition to feelings, thoughts, and situations surrounding the eating event. Nutritional information and calculations can be included, such as calories, fat grams, carbohydrate servings, sodium, and others. Accuracy depends on the person’s memory, completeness of reporting, and the interviewing and communication skills of both the patient and the evaluator.
The data gleaned from any dietary assessments should be interpreted with caution, however, because retrospective and even prospective underreporting and overreporting are common. FFQs are self-administered tests with multiple questions about frequency of consumption and portion size of many different foods over the prior 1 month or 3 months. Questions in FFQs also may include information on food purchasing and preparation methods. FFQs can help identify inadequacy or overconsumption of specific food groups, or patterns of specific foods or preparation methods. Like the food diary, the FFQ can offer a more real-life assessment of the patient’s typical food choices because it can be completed outside of the provider’s office.
Reduced levels of physical activity can be a major factor in the etiology of obesity and may be a direct result of acute or chronic illness, job change or retirement, or just sedentary lifestyles in general, such as more television viewing or screen time (34, 35, 36, 37). An inventory of the person’s usual physical activity and preferred forms of exercise can identify opportunities for increasing the level of energy expended through physical activity. Food record forms can include a place for physical activity, which can be helpful in discussing exercise habits and goals. However, the provider must recognize and communicate that exercise alone is, unfortunately, not an effective method for losing weight. It is difficult for the untrained person to do enough of it, and most, if not all, of the expended
energy may be compensated by increased caloric intake. Exercise is a very good way to maintain a lower weight after weight loss, thus enabling a person to eat somewhat more than a nonexerciser and maintain weight. Regular aerobic exercise and strength training also will improve cardiovascular fitness, trim inches, and promote growth of metabolically more active muscle tissue.
energy may be compensated by increased caloric intake. Exercise is a very good way to maintain a lower weight after weight loss, thus enabling a person to eat somewhat more than a nonexerciser and maintain weight. Regular aerobic exercise and strength training also will improve cardiovascular fitness, trim inches, and promote growth of metabolically more active muscle tissue.
The exercise assessment should include a record of the usual degree of physical activity, any limiting factors such as joint disease or previous injuries, types of activity the patient finds enjoyable, and a measurement, preferably by an exercise physiologist or certified trainer of the current fitness level. Physical activity level can be assessed broadly by inquiring about the amount of walking done in a day, flights of stairs climbed, and hours of television watched (38). More formal assessment can be conducted using a pedometer to determine the number of steps walked daily, or an accelerometer, which also can assess the intensity of activity.
A rule of thumb in prescribing an exercise regimen is to use a phased-in approach. Most obese patients start out with a limited capacity to exercise. Rather than suggesting a type or level of activity that is unlikely to maximize adherence, make sure that the plan fits the patient’s current abilities, schedule, and lifestyle. The first phase often consists of increasing the amount of everyday physical activity, so-called lifestyle activity, without introducing a formal exercise regimen. Lifestyle activities include taking the stairs in gradually increasing fashion, parking the car farther away from the destination, walking to the mailbox, and the like. This phase alone may double the level of physical activity in a very sedentary person.
The next phase is a walking plan. People are most likely to comply with such a plan if the walk is scheduled during typically available times, such as a break or lunchtime during work hours. Scheduling exercise when the individual’s daily energy level is the highest (e.g., early morning for many people) is often more effective than at the end of a long day. Having a companion to walk with and a place to walk indoors also are helpful in increasing adherence.
One half hour is a good minimum time to recommend that a patient should make available for each session of exercise. An hour or longer is best for weight control. The intensity of the exercise is not critical to the burning of calories: walking at a leisurely pace for 1 hour is roughly equal to walking briskly for half an hour. Allow the patient to set the pace. Initially, it may be quite slow, but in the absence of severe pulmonary, cardiovascular, or joint disease, most patients soon find the going easier and faster. Goal setting can strengthen this reinforcement. Having the patient keep a log of the time spent walking and the distance covered after each session is useful. The patient can then see the progress being made and can set the goal a bit higher as warranted.
In the next phase of a progressive exercise plan, the types of activities performed should be broadened. Walking or jogging can and should remain a feature at this stage, but with the addition of other forms of aerobic exercise. Perhaps recommend aerobics classes, stationary or outdoor bicycling, swimming, a cross-country skiing machine, or just about anything else that will burn calories and be enjoyable to the patient. Team or racquet sports and golf can be suggested to provide social interaction, as well as to increase energy expenditure. Again, the most important criterion for a good exercise plan is one that the patient is likely to follow and be comfortable with as a lifelong habit.
Weight Loss Readiness
Successful weight loss can be achieved and maintained when the obese individual is determined and motivated. For this, the provider must assess and evaluate the readiness state of the individual. It is essential for the obese individual to be motivated to make lasting lifestyle changes; however, internal self-motivation is more sustainable than external motivators such as a spouse’s demands or the anticipation of a special event. The stages of change model for behavior change intervention may be useful in assessing where an individual is with regard to making behavior changes and in helping the individual move along the continuum from precontemplation to action stages (39). Although internal motivation is the key to successful weight loss and maintenance, external stimuli, such as support from friends and family, and environmental factors, such as easy access to healthful foods and safe places to walk and run, also play important roles. Garnering these support systems can assist the individual to be mentally ready to move along the path of the action stage of weight loss and then weight maintenance efforts.
The provider should assist the obese individual to set goals that are “smart goals” (i.e., ones that are specific, measurable, achievable, realistic, and timely) because such goals are more likely to be achieved. Social support from family and friends also can improve the likelihood of success in making behavior changes. Enlisting help from others (e.g., in keeping trigger foods outside the house and in trying healthier foods) has been shown to improve the chances of success (40). In addition to support from family and friends, online or local weight loss support groups provide opportunities for discussing challenges and giving or receiving support. These can improve a patient’s outcome both during and after initial treatment.
SELECTING THE RIGHT TREATMENT
Initial weight loss should be achieved with a comprehensive program that includes dietary changes, increased physical activity, and behavior modification. The recommended rate of weight loss depends on the degree of obesity, the presence or absence of comorbid conditions, the results of behavioral assessment, and patient preference. According to NHLBI guidelines (20),
overweight individuals (BMI = 25 to 29.9 kg/m2) without any associated risk factors should be encouraged to prevent further weight gain or lose weight with simple dietary modifications. However, if this condition is accompanied by one or more cardiovascular risk factors, lifestyle modification is recommended in which diet, exercise, and behavior therapy may be helpful. Similarly, for individuals with moderate obesity (BMI >30 kg/m2) and no additional risk factors, lifestyle modifications are beneficial, aiming for a rate of weight loss of l to l.5 lb/ week (a calorie deficit of 500 to 750 kcal/day), a rate that is generally safe and rapid enough to sustain motivation. However, for individuals with BMI greater than 30 kg/m2, or greater than 27 with medically important comorbid conditions, if lifestyle modifications alone are not successful, pharmacologic interventions may be an option. For individuals with severe obesity (BMI >35 kg/m2 with comorbidities, or >40 kg/m2 without), more aggressive energy restriction under medical supervision may be preferable. In the presence of significant comorbid conditions for individuals with severe obesity, bariatric surgery is an option to be considered as well.
overweight individuals (BMI = 25 to 29.9 kg/m2) without any associated risk factors should be encouraged to prevent further weight gain or lose weight with simple dietary modifications. However, if this condition is accompanied by one or more cardiovascular risk factors, lifestyle modification is recommended in which diet, exercise, and behavior therapy may be helpful. Similarly, for individuals with moderate obesity (BMI >30 kg/m2) and no additional risk factors, lifestyle modifications are beneficial, aiming for a rate of weight loss of l to l.5 lb/ week (a calorie deficit of 500 to 750 kcal/day), a rate that is generally safe and rapid enough to sustain motivation. However, for individuals with BMI greater than 30 kg/m2, or greater than 27 with medically important comorbid conditions, if lifestyle modifications alone are not successful, pharmacologic interventions may be an option. For individuals with severe obesity (BMI >35 kg/m2 with comorbidities, or >40 kg/m2 without), more aggressive energy restriction under medical supervision may be preferable. In the presence of significant comorbid conditions for individuals with severe obesity, bariatric surgery is an option to be considered as well.
DIETARY INTERVENTION
Weight gain is always a result of excess energy intake compared with energy expenditure. This creates a state of positive energy balance, eventually resulting in obesity or in greater obesity for those already obese (41). Although certain circumstances can increase energy intake and decrease energy expenditure, in the United States typically, volitional or semivolitional increases in food intake along with sedentary lifestyle are what throw off the balance between energy input and energy output.
Although diet therapy remains the cornerstone of weight loss (42), adherence to diet is often difficult for those trying to lose weight, with failure to follow the recommended diet consistently. Although the diet often recommended contains 50% to 55% of calories from carbohydrates, less than 30% from fat, and 15% from protein (42), low satiety, palatability issues, and lack of variety are often experienced, resulting in low adherence to standard, heart-healthy diets (42). A low-fat, low-refined carbohydrate diet allows for less restriction in the volume of food consumed because fatty and processed foods are more energy dense.
To lose weight at 1 to 2 lb/week, a healthy rate of weight loss as recommended by NHLBI guidelines (20), a calorie deficit of 500 to 1000 calories/day is required. Both dietary intake restriction and increased exercise can contribute to the energy deficit required (3500 calories = 1 lb of fat). Low-calorie diets (LCDs) contain 800 to 1500 kcal/day; on occasion, very-low-calorie diets (VLCDs), which contain fewer than 800 kcal/day, may be necessary to lose weight adequately among individuals with severe obesity, especially when they have serious comorbid conditions. VLCDs should be used under medical supervision (20).
Moderate Energy-Deficit Diets
Moderate energy-deficit diets (1500 to 1800 kcal/day) follow the guidelines laid out by the US Department of Agriculture Dietary Guidelines for Americans (43). A caloric deficit of 500 calories/day can be created to achieve approximately 1 lb of weight loss/week. The provider can design a low-calorie, food-based diet that has either a balanced deficit (reducing total number of calories while keeping proportions from carbohydrate, fat, and protein roughly the same as before) or a fat deficit (with most of the caloric reduction resulting from restriction of fat intake). The fat-deficit approach may be preferable for individuals consuming too much fat, especially saturated fat. In addition, a greater volume of food can be eaten on a diet that emphasizes complex and vegetable-source carbohydrates and reduces fat to less than 30% of calories consumed.
Restricting dietary fat is an approach that can serve to minimize hunger while maximizing satiety by replacing dietary fat with complex carbohydrates such as fruits, vegetables, and whole grains, which are less energy-dense (lower calorie), higher in fiber and water content, and more filling than foods with higher energy density, which tend to be higher in fat and sugar content. Moreover, research shows that the US population consumes diets that are high in fat and sugar and low in fiber (44, 45, 46), which are associated with high energy density and subsequent weight gain (47, 48, 49, 50). This dietary approach to reduce weight often works, at least short term; because gram for gram, fat has more than double the calories of carbohydrates or proteins (9 versus 4 calories/g). For this reason, teaching individuals how to eat a larger volume of food for any given number of calories by focusing on a combination of complex carbohydrates and lean proteins is invaluable. In addition, lowering fat intake can help boost metabolism because fewer calories are used to convert dietary fat into body fat compared with carbohydrates and proteins. A relatively low-fat diet can improve cholesterol and reduce risk for chronic disease as well. Finally, these diets may be easier to adhere to because small changes are required in eating habits (e.g., cutting out hidden fats and simple sugars).
Low-Calorie Diets
For patients with BMIs between 25 and 34.9, especially those with comorbidities such as type 2 diabetes or high blood pressure, an LCD (800 to 1500 kcal/day) is appropriate as a first-line approach. This diet provides 800 to 1500 kcal/day. Research shows that for those with a starting BMI greater than 30, these diets are helpful in producing a typical loss of more than 8% of initial body weight over 3 to 6 months of treatment, with substantial health benefits (51, 52, 53). However, diet therapy combined with intense behavioral therapy and support is essential to losing and maintaining the weight loss. These diets can vary in protein, carbohydrate, and fat content (53).
Very-Low-Calorie Diets
Individuals with severe or morbid obesity (BMI >40) can benefit from a moderately restricted diet; however, it typically will take at least 1 year of steady dieting to lose 50 lb with this modest level of energy restriction. Few individuals can sustain even a moderately restrictive diet for this long. Thus, it may be reasonable for such patients to begin with a period of more severe energy restriction under medical monitoring. VLCDs, defined as containing fewer than 800 kcal/day, may be food based or may use meal replacements, often in the form of soy, egg, or milk-based high protein, low-carbohydrate, low-fat shakes or bars, containing vitamins and minerals to prevent nutrition deficiencies.
This approach can be quite useful if it is monitored and accompanied by a comprehensive program of behavior modification and physical activity. Initial, but usually temporary, side effects may include hunger, fatigue, and lightheadedness; later on, constipation and intolerance to cold may occur. The increased risk of developing gallstones (54) may be transient. Studies show that weight loss of 10% to 20% can be achieved initially with VLCDs (55, 56, 57, 58, 59, 60); however, adherence for more than several months may not be sustainable. A high protein content consumed during a VLCD may minimize muscle wasting as the rapid weight loss occurs (61). The main drawback of VLCDs is frequently rapid weight regain after the weight loss phase (62). Thus, use of VLCDs is most effective in the context of a well-rounded, multidisciplinary approach to weight loss and long-term weight control. Careful attention to a weight maintenance program is essential following a VLCD. VLCD programs should encourage exercise and provide ongoing support, perhaps with groups, classes, or individual sessions.
Low-Carbohydrate, High-Protein Diets
Low-carbohydrate diets typically recommend up to 20 g of carbohydrate at the onset of the diet (e.g., the Atkins diet), with a high intake of protein and fat (63). This diet typically involves three phases. The first phase is called the induction phase, which is the weight loss initiation phase and includes no more than 5% of energy from carbohydrate, 35% from protein, and 60% from fat (63). The second phase, called the ongoing phase, is a continuation of weight loss, with the proportions of carbohydrate (9%), protein (33%), and fat (58%) slightly liberalized. The third phase is the maintenance phase, in which carbohydrate intake increases to no more than 20% of total energy with 25% to 27% protein and approximately 52% fat.
Any restrictive diet can cause diuresis in the initial 1 to 2 weeks, resulting in 2% to 4% weight loss largely because of water loss (64). Evidence from several studies indicates that low-carbohydrate diets are initially more effective compared with diets low in fat and calories for weight loss and improving cardiovascular risk factors associated with obesity (65, 66, 67, 68, 69). However, no significant differences are present between diets after 1 year (65, 66, 67, 68, 69). Lower attrition rates also are observed with the low-carbohydrate diets, perhaps because of higher satiety associated with high intakes of protein (70).
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