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Current Management of Obesity
Lawrence J. Cheskin, M.D., and Scott Kahan, M.D., M.P.H.

Dr. Cheskin is the Director of the Johns Hopkins Weight Management Center and Associate Professor of Medicine and Public Health at Johns Hopkins University; Dr. Kahan is the Associate Director of the Johns Hopkins Weight Management Center and on the Faculty of the Johns Hopkins University Preventive Medicine Residency Program.

Within the past 12 months, Dr. Cheskin has been a consultant for Medifast, Inc., and Vivus, Inc. Dr. Kahan reports no commercial conflicts of interest.

Albert Einstein College of Medicine, CCME staff and interMDnet staff have nothing to disclose.


Release Date: 04/05/2010
Termination Date: 04/05/2013

Estimated time to complete: 1 hour(s).

Albert Einstein College of Medicine designates this enduring material for a maximum of 1.0 AMA PRA Category 1 Credit(s)™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

Albert Einstein College of Medicine is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.
 
Learning Objectives
Upon completion of this Cyberounds®, you should be able to:
  • Describe the epidemiologic trends of overweight and obesity in the United States
  • Explain the etiology of overweight and obesity
  • Perform the medical and nutritional assessment of overweight and obese patients
  • Apply the medical, nutritional and lifestyle approaches for management of overweight and obese patients.

 

Obesity is considered by many to be one of the gravest health threats of our generation. Rates of overweight and obesity in the U.S. have risen at epidemic proportions over the past two decades. Medical complications of obesity are significant and deaths attributable to obesity approach the number attributable to tobacco abuse. Despite this, we have yet to find a “cure” or a consistent treatment that successfully addresses more than a minority of obese patients.

Sixty−six percent of Americans are either overweight or obese.

Epidemiology

Approximately 110 million American adults are overweight. Sixty−six percent of Americans are either overweight or obese.(1) If current trends continue, it has been estimated that nearly all American adults will be overweight or obese by 2030.(2) The prevalence of childhood obesity and extreme obesity have increased dramatically.(3) Even developing nations are seeing an increase in obesity and obesity−related complications, in part related to the adoption of a Western diet and exercise patterns.

There are significant ethnic disparities in rates of overweight and obesity. Rates of overweight in African−American and Mexican−American women are approximately 35% greater than age−adjusted rates for Caucasian women; rates of obesity in African−American and Mexican American women are approximately 50% greater than the rates for age−adjusted Caucasian women.(4)

Obesity is neck and neck with cigarette smoking as the most important modifiable medical risk factor, and affects risk of diseases of virtually every organ system, including certain cancers (Table 1).(5)

Obesity is the most important risk factor in the development of type 2 diabetes.

Table 1. Major Health Risks of Obesity.

Type 2 diabetes Hypertension
Coronary artery disease Gallbladder disease
Dyslipidemias Gastroesophageal reflux disease
Strokes Nonalcoholic fatty liver disease (NAFLD)
Carcinoma (especially endometrial, colorectal, esophageal, post-menopausal breast) Osteoarthritis
Sleep apnea Gout
Infertility Thromboembolism

Obesity is the most important risk factor in the development of type 2 diabetes, the sixth leading cause of death in the United States. Prevalence of hypertension and hyperlipidemias increase significantly in patients who are overweight, compared with normal weight patients, and in patients who are obese, compared with overweight patients. Obesity also increases overall mortality, and has recently been shown in Framingham and other populations to shorten life expectancy by a mean of at least several years.(4)

In addition to the medical risks of obesity, these patients face unfortunate psychosocial consequences of their obesity (though the desire to avoid these psychosocial factors strongly motivate many people to try to lose weight). There is widespread prejudice against obese individuals, even detectable in the opinions of young children. The resulting social and job discrimination contributes to low self−esteem and the high rate of depression among obese people who seek treatment. In American society, obese women, compared to obese mean, bear much greater social stigma.

No other field of medicine is as subject to fads and hype, as well as to unreasonable patient expectations, as is obesity treatment. Part of the reason lies in the inherent difficulty of reconciling a society whose main fuels are high caloric density and tasty with an ideal “Barbie doll” body type.

Despite the inescapable fact that adiposity reflects strong genetic influences (evidenced by adopted child and twin studies, as well as by the increasing number of genetic markers being discovered), genetics does not appear to account for the majority of variability in body mass index (BMI) seen in the population. Both the environment and learned behaviors are significant modifiers of genetic predisposition.

The long−term success rate, defined as losing weight and keeping most of it off for five years, is low, perhaps 5 to 15% from the limited data provided by published studies.(7) Although this success rate is low, it must be viewed in context and compared with our similarly poor success in treating other chronic conditions and addictions (e.g., cigarette smoking and drug abuse). In fact, if one views the chronic pleasurable overconsumption of food energy as a kind of addiction, an instructive distinction between food and other reinforcing substances appears. The cigarette smoker need never smoke again; the obese person, however, must learn to coexist with the offending substances in order to live. As such, we cannot expect many complete cures and we will need to be constantly on the alert for relapses in those who appear to be in remission.

Medical Assessment

The first step in treating the obese patient is the medical evaluation. Obesity is defined as an excess of body fat (>25% of body weight for men and >30% for women) rather than an excess of body weight per se. However, the measurement of percent body fat is more difficult to obtain and not as intuitive as body weight. Thus, relative weight is a reasonable surrogate measure for adiposity (percent of body weight constituted by fat).

Central obesity can exist even in the absence of overall obesity.

Weight adjusted for height, or body mass index (BMI), defined as weight in kilograms divided by the square of the height in meters, is most commonly used for defining and grading the severity of obesity and its attendant risks. Overweight is defined as a BMI of 25 to 30 kg/m2 and obesity is defined as BMI greater than 30 kg/m2. BMI is now the standard measure of relative weight, though it may be a poor reflector of the actual degree of adiposity in very muscular individuals (e.g., certain types of athletes and laborers) and may understate adiposity in very sedentary individuals with little muscle mass.

The risk of complicating medical conditions increases with the degree of excess body weight, although for some complications, notably coronary artery disease, type 2 diabetes and stroke, the risk correlates best with the regional distribution of fat. Central (visceral) deposition of fat (the “apple−shape” pattern), seen more commonly in men, increases risk, while excess fat in the lower body (thighs, hips and buttocks), seen more commonly in women (the “pear−shape” pattern), is associated with a lower risk of such complicating conditions.

In the case of central obesity, even mild excess adiposity may pose a medical problem. It should be noted that central obesity can exist even in the absence of overall obesity (i.e., at BMIs below the cutoff point for obesity or even below the cut−off point for overweight). A waist circumference of more than 40 inches for men and more than 35 for women suggests the diagnosis of abdominal obesity, and can be measured with a tape rule around the widest point above the navel. Fortunately, this metabolically active abdominal fat is usually the first fat depot to diminish with weight loss.

Medical History

In addition to a standard medical history, the weight history may be of value in identifying precipitants of weight gain. The weight history may additionally suggest both avenues of treatment to pursue and avenues to avoid. For example, a change in job leading to a reduction in physical activity may be detected. Also of interest is whether the onset of obesity was in childhood or later in life. Although only one−fifth of obese adults were obese children, about four−fifths of obese children go on to become obese adults. Obesity in childhood can result in an increase in average cell number (hyperplasia) not just size (hypertrophy), while hyperplasia occurs less frequently in adults, usually only when rapid weight gain occurs. Treatment of the hyperplastic form of obesity is said to be more difficult for both children and adults because weight reduction does not greatly reduce the number of fat cells, only their average size.

Other information that can be gleaned from the weight history include postpartum weight gain (the average woman weighs about 10 lbs more two years postpartum compared to pre−pregnancy, but the amount is extremely variable) and weight gain after smoking cessation [average gain of about 6 lbs (again highly variable and the most common reason women give for not wanting to quit smoking)]. It is also important to elicit evidence of yo−yo dieting and eating disorders such as binge eating (consuming very large amounts of food within a specified period three times a week or more, in private, for more than one year, with loss of control and negative emotional sequelae) or bulimia nervosa (bingeing plus purging, either by vomiting, use of diuretics or excessive exercise).

Depression commonly accompanies severe obesity.

The history should assess for secondary, and potentially treatable, causes of obesity. These include endocrine disorders such as hypothyroidism, hyperadrenalism and neuroendocrine tumors (although even the most common of these, hypothyroidism, is rarely a significant cause of obesity in adults); psychiatric disorders; and pharmacologic agents which are associated with weight gain such as sulfonylureas, insulin, steroids, most antipsychotics and certain antidepressants.

The history should also assess for symptoms suggestive of diseases that often complicate obesity such as type 2 diabetes, coronary artery disease, hypertension and obstructive sleep apnea. Symptoms and signs of depression should also be sought, as depression commonly accompanies severe obesity and may require additional treatment. Childhood or adult sexual and physical abuse is also common. Because patients do not usually voluntarily disclose these histories, they need to be specifically elicited after rapport has been established with the patient. The family history is of particular interest for endocrine disorders, extreme obesity and its complications.

Physical Examination

The physical examination may be somewhat limited when the patient is extremely obese, but it can yield evidence of endocrine and other secondary causes of weight gain, as well as signs of complicating conditions. It is necessary to obtain not only an accurate weight and height for calculation of the BMI, but also tape measurement of the waist circumference, which, as noted, is an important modifier of the risk in obesity.

Laboratory Examination

Laboratory evaluations should serve to screen for the complications of obesity. Blood chemistries should include fasting serum glucose, cholesterol and triglycerides, and liver tests. A thyroid−stimulating hormone (TSH) level and other endocrine and metabolic tests should be obtained if there is clinical suspicion.

Behavioral Assessment

It is critical to gain a sense of the patient’s behavioral triggers of obesity. This can be accomplished by referral to a behavioral psychologist with experience treating obesity, and/or through your own discussions with the patient.

First, it is important to assess the impact of the obesity itself on the patient’s level of functioning and quality of life. Some very important aspects of the patient’s problem may only emerge with specific inquiry. Some possibilities: the patient may have withdrawn from all unnecessary social interactions; or may no longer be able to enjoy certain activities or interests because of weight gain; or may have suffered job discrimination. Also related to quality of life are the patient’s expectations about what changes will occur with successful weight control. Although it may be motivating for the patient to believe that life will improve with weight loss, disappointment may follow unless the changes likely to occur have been placed in proper perspective.

Medical benefits can certainly be expected with weight loss in many of those suffering from medical complications of obesity. Patients with type 2 diabetes can often discontinue insulin or oral agents, antihypertensive medications may become unnecessary and sleep apnea usually disappears with as little as a 10 to 15% loss of initial weight. On another level, however, although self−assurance often increases, the wallflower does not become the life of the party and the average, competent worker does not get a promotion upon losing weight. Encourage obese patients toward a balanced view by reminding them that societal prejudices about body weight and character are in no way based on fact, and that they are the same good people whether they weigh 300 or 150 lbs.

Help patients identify their specific triggers to eating.

Behavioral Factors

Most obese individuals do not experience more physical hunger than do lean people, but they may misinterpret learned habits and situations that lead to eating as “hunger.” A major breakthrough in the ability to control unnecessary eating can result when individuals learn to accurately distinguish physiological from learned forms of hunger, and respond appropriately.

It is useful to help patients identify their specific triggers to eating. These eating cues are situations or feelings that lead to eating, often in an inappropriate way. In our society, physical hunger is rarely a significant part of life, even for the poorest among us. In fact, physical hunger is not an important eating cue for many people, in part because they rarely let themselves get to the point of true hunger. Instead, they may eat in response to a host of other cues, most of which are inappropriate.

The most common eating cues cited are: habit (“It’s noon so I guess I’ll have lunch” or “I always have a jelly doughnut and coffee in the car on the way to work”), stress (“I’ve got to finish this paper and eating while I write helps me concentrate”), boredom (“There’s nothing else to do”), emotions (“I eat when I’m depressed or upset”) and food as a reward (“After a hard day, I deserve a rich dessert”). Underlying some of these cues is the association of food with love, caring and comfort, which may have its antecedents in early childhood but persists into adult life and is pervasive in our culture. The patient should be helped to recognize that using food to deal with stress, boredom and emotions is, at best, ineffective. The stressful situation does not resolve with eating. In fact, eating may worsen the problem by distracting a person from dealing directly with the situation.

Another behavior of interest in obesity is dietary restraint. Restrained eaters believe that they must exercise a good deal of control over their eating—they are always conscious of what they can and cannot eat. Unrestrained eaters do not control their eating to any great extent. Restrained eating may lead to some paradoxical sequelae: once restraint is relaxed an exaggerated response may follow (all−or−nothing behavior). Such patients may be superb dieters but are equally superb at overeating once the diet has been “broken.” Although a certain amount of control and monitoring are necessary to maintain weight control, in the long run a high level of dietary restraint may be more problematic than a low level of restraint, that is, it may lead to release of restraint.

Dietary Assessment

Though most aspects of diet are more properly characterized as behaviors, the need remains to understand patients’ tastes and food choices. The physician can and should get some idea of the patient’s diet but a formal dietary assessment is best done by a dietitian, using either a prospective or retrospective food diary.

The results of a food diary must be interpreted with caution, as both retrospective underreporting and prospective restrained eating are more common among obese individuals (and may in fact explain some of the propensity towards obesity if the obese are less aware of the foods and quantities they choose). Despite these shortcomings, the information gathered can be very useful. The clinician often learns, for example, that the macronutrient composition of the patient’s diet is weighted toward fats and low−fiber carbohydrates. By cutting fat and increasing intake of high fiber/water content carbohydrates, especially vegetables and fruit, such patients can considerably increase the volume of food they consume with less physical hunger as they attempt to reach and maintain a lower weight.

Exercise Assessment

Exercise assessment should include an exploration of the patient’s usual degree of physical activity, limiting factors (such as joint disease, previous injuries or environmental limitations), types of physical activity the patient finds enjoyable and a measurement, preferably by an exercise specialist, of the patient’s current fitness level. An exercise stress test is generally not required unless cardiovascular disease is suspected.

Treatment

For most patients, only a modest degree of weight loss is realistic. However, this should not be viewed as a failure or a waste of time. It should be noted that even a modest weight loss can yield substantial health benefits for morbidly obese patients. Sleep apnea often disappears with as little as a 10% loss in weight. With even 5−7% weight loss, hypertension, diabetes and hyperlipidemias may improve significantly.

Dietary and Behavior Modification

Simply telling a patient not to eat when under stress is generally ineffective, given the longstanding habit of many obese patients to use food inappropriately. Instead, the physician should try the following 3−step approach. First, recommend a period of observation and recording to enable the patient to recognize the cue. For instance, you can ask the patient to wear their watch upside−down as a reminder of “Why am I reaching for the food at this time?” If the patient is not physically hungry, an inappropriate eating cue is most likely occurring and its nature should be recorded. Second, suggest the substitution of other responses for inappropriate eating. For stress, this might be writing down what the stress is, formulating a plan for doing something about it, doing something (besides eating) to relieve the stress on the spot or, at the very least, substituting the food with a walk around the block or a call to a friend. The third step is repetition — the patient practices making appropriate responses to the problematic cue. The rewards of substituting a new behavior include the positive responses of others to the change in approach—not just to eating, but to life—that the patient makes.

Although some degree of behavior change is necessary, not every maladaptive behavior must be completely eliminated and not every rich food replaced. While losing a large amount of weight in a reasonable amount of time does require a fairly aggressive diet program, maintaining a new lower weight does not. If the patient can learn to partially control even a few of his or her more important inappropriate eating behaviors and shift to a diet somewhat lower in calories than baseline, these changes are often sufficient to maintain weight in the new, lower range.

Behavior modification may include coupling strategies for controlling inappropriate eating cues with dietary changes that emphasize foods lower in fat and calories and higher in fiber and water content (i.e., low energy−density foods), so that less dietary restraint is required to maintain a given intake. Skipping meals when the patient is physically hungry should be discouraged.

Gradual change is a helpful technique that can alter the composition of the patient’s diet. A patient reluctant to switch from whole milk to skim milk could, for example, first try 2% milk, get used to this for a month or so, then move on to 1% fat milk for another month. At this point, the patient should notice that the once−favored whole milk will now taste too oily. At some later date, the final step to skim milk can be made with few feelings of deprivation, demonstrating to the patient that taste preferences are acquired and eminently changeable, even in later life.

Recommend scouring the supermarket aisles (at a time when the patient is not hungry) for tasty, low−fat, low−calorie alternatives to favored foods. Encourage the patient to explore the wide variety of foods now available and to focus on the good taste of the new choice rather than comparing it to the “real thing.” The presentation of nutritional information on food labels is becoming more and more useful, listing not just grams of fat, for example, but also the percentage of the daily dietary fat allotment those grams represent. The patient should be taught to read labels and to stay within the calorie “budget.”

...Instill in your patients a degree of skepticism about commercially advertised weight−control diets.

This is also a good time to improve the dietary habits of the patient’s family, something that is particularly easy to do when the patient is the primary cook and food shopper. Including the family in this process not only improves their diet, but also makes it easier for the patient if the home can be a temptation−free zone. If other members of the family insist on consuming junk food, they can be instructed to partake outside the home or to put only individually packaged items in the cupboard. Small−size purchases of rich desserts and the like are desirable in general—the smaller the dietary indiscretion, the less severe the consequences. Unfortunately, portion sizes have risen greatly in the U.S. in recent years, especially in meals consumed outside the home.

It is best to instill in your patients a degree of skepticism about commercially advertised weight−control diets. Many are based on very limited menus, the rationale being that monotony helps curb consumption. Some nonprescription dieting agents have diuretic actions. In fact, any substantially reduced−calorie diet will initially cause diuresis, but the fluid−based weight loss will be regained as soon as the period of severe caloric restriction ends.

For overweight patients, a caloric deficit of 500 to 750 calories per day to achieve 1 to 1.5 pounds of weigh−loss per week may be appropriate. A dietitian can design a low−calorie, food−based diet that is either balanced−deficit (reducing total number of calories, while keeping proportions from carbohydrate, fat and protein roughly the same as before), or fat−deficit (with most of the caloric reduction resulting from restriction of fat intake). The latter approach is preferable because the typical American diet is too high in fat, especially saturated and trans fats, and simple sugars. Also, a greater volume of food can be eaten on a diet that emphasizes fiber−rich complex and vegetable−source carbohydrates, and reduces fat to 30% of calories consumed.

A highly restricted diet should be administered only under a trained physician's supervision.

Obese patients will also benefit from a fat−and−calorie−reduced diet. It is important, however, to recognize that at this level of caloric restriction it will take more than a year to attain a weight−loss of 50 to 70 pounds. Few patients can sustain this degree of restriction for that long; therefore, for a limited period of time, a physician−supervised −low−calorie diet of fewer than 1200 calories per day may be appropriate. More restrictive diets are justified particularly if the patient already suffers from co−morbidities that are likely to be alleviated with significant weight loss.

Low−calorie diets can consist of regular food, commercially available meal replacements or a combination of both. With full compliance, the amount of weight lost on a LCD ranges from 1.5 to 4 pounds per week, depending on body mass and level of physical activity. A highly restricted diet should be administered only under a trained physician’s supervision and with full attention to the behavioral changes necessary to sustain the weight loss that this regimen will produce.

Physical Activity

Despite the multiple medical benefits of exercise, in the absence of concurrent dietary change, exercise will not produce weight loss. This may be due to increased hunger secondary to exercise, partially or largely counterbalancing the calories burned in the exercise, which may be of evolutionary advantage.

Exercise is, however, an excellent aid to maintaining a lower weight after weight loss, enabling a person to eat somewhat more than a non−exerciser and still maintain their weight. Regular aerobic exercise and strength training will also improve cardiovascular fitness, reduce adipose tissue depots (especially visceral fat), promote growth of metabolically more active muscle tissue and often results in substantial improvements in mood.

A rule of thumb in devising an exercise regimen that will be most likely to be followed is to utilize a phased−in approach. Most obese individuals start out with a limited capacity to exercise. Rather than suggesting a type or level of activity that is high, and unlikely to lead to sustained adherence, make sure that the plan fits into the patient’s schedule and lifestyle.

The first phase consists of increasing the amount of everyday physical activity, so−called “lifestyle” activity, rather than prescribing a formal exercise regimen. Lifestyle activities include taking the stairs in gradually increasing increments, parking the car farther away from the destination, walking the dog farther and similar modifications. This step alone may double the level of physical activity in a very sedentary individual.

An hour of exercise is best for weight control and 90 minutes for weight loss.

The next phase is a structured walking plan. People are most likely to adhere to a plan if the walk is scheduled during a break or lunchtime at work, or when their daily energy level is often the highest (for example, early morning, as opposed to evening after a long day’s work). To increase compliance, it helps to walk with a companion and to be able to walk indoors.

A patient should make a minimum of 20 to 30 minutes available for each session of exercise. Studies suggest that an hour is best for weight control and 90 minutes for weight loss. The intensity of the exercise is not critical to the burning of calories: walking at a leisurely pace for one 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, cardiopulmonary or joint disease, most patients soon walk faster and find the exercise easier. Goal setting can strengthen this process. Have the patient keep a log of the time spent walking and the distance covered after each session. The patient can then see the progress being made and regularly set the goal a bit higher.

Next, the type of activities performed should be broadened. Walking or jogging can and should remain a component of the plan, but with the addition of other forms of aerobic exercise. 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. Strength/resistance training of large muscle groups is an important component to include, as this can build muscle mass and raise resting metabolic rate, an aide to future weight control. Team or racquet sports and golf can be suggested to provide social interaction and thus increase the likelihood of long−term adherence to the exercise plan. Again, the most important criterion for a good exercise plan is that it be one that the patient is likely to follow and be comfortable with as a life−long habit.

Drugs and Surgery

Adjunctive anorectic medications may be useful for the obese patient, either initially to enhance dietary compliance or later when compliance begins to waver or hunger becomes more prominent. There is little doubt that such medications significantly increase weight loss during the period in which they are used, and may help maintain some weight loss (although regain tends to occur even with continued use). Commonly used anorectic drugs are phentermine and sibutramine. One reasonably effective agent, ephedra, is no longer available because it has been associated with adverse cardiovascular events.

An additional agent for weight loss is orlistat, which is sold by prescription as Xenical and in a nonprescription strength, labeled as Alli. This is the only non−systemically−acting obesity medication currently available. It acts in the lumen of the small bowel by binding to lipases and causing malabsorption of about 25−30% of ingested fat (depending on dosage). These agents also block the absorption of cholesterol and fat−soluble vitamins, so the patient taking orlistat will need multivitamin supplementation. While orlistat and Alli have no appetite−curbing effects, they may have a behavioral, Antabuse−like effect in that consumption of more than a moderate amount of fat at a sitting will result in unpleasant GI consequences. This agent may be more suitable for patients who are having difficulty avoiding junk food and fats than for patients with increased physical hunger.

Surgical treatment of morbid obesity has improved considerably in recent years.

Herbal medications are also widely used for weight control. Agents that appear to have limited efficacy include fiber supplements, ephedra−like agents (e.g., citrus aurantium) and conjugated linoleic acid. Many other agents have been advertised for weight loss (e.g., DHEA, chromium picolinate, hoodia gordonii, chitin/chitosan) but do not appear to have a clinically significant effect. It is important to recognize that herbal agents are drugs and can be as toxic as synthetic pharmaceuticals. Moreover, few are subjected to the degree of scientific scrutiny that pharmaceuticals undergo.

The surgical treatment of morbid obesity has improved considerably in recent years. Generally, patients are referred for surgery only if they have a BMI of 40 kg/m2 or greater, or of 35 kg/m2 or greater if there are significant coexisting medical complications of obesity and they have failed to lose or maintain weight loss with a comprehensive, non−surgical approach.

Gastric bypass surgery, preferably performed laparoscopically, results in the most significant initial weight loss among surgical interventions. This procedure combines “stapling” of the stomach to make a small−capacity proximal gastric pouch along with a short−segment bypass of the proximal small bowel to decrease nutrient absorption. Though short−term results are impressive in most patients, long−term outcomes, as with all methods of weight loss, depend largely on the patient’s ability to make sustained behavioral changes. Therefore, aside from access to a hospital with adequate experience in this procedure, the best chance of long−term success is to refer the patient to a center that offers and insists upon extensive preoperative evaluation and long−term maintenance therapy consisting of regular sessions in dietary management and behavioral modification.


Footnotes

1Centers for Disease Control and Prevention. http://www.cdc.gov/obesity/causes/health.html
2Wang, Youfa. Beydoun MA, Liang L, Caballero B, Kumanyika SK. Will all Americans become overweight? Obesity 2008; 16(10):2323-30.
3Sturm R. Increases in morbid obesity in the USA: 2000-2005. Public Health 2007;121:492-6.
4NHLBI Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults. National Institutes of Health Publication No. 98-4083. September 1998.
5Mokdad AH, Marks JS, Stroup DF, Gerberding JL. Actual causes of death in the US, 2000. JAMA 2004;291:1238-45.
7NIH consensus statement. Ann Int Med 1993; 119:764.