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REE), obtained either by metabolic cart or estimation

formulas, is then used to determine daily caloric needs

by multiplying RMR by an activity factor ranging

from 1.3 (for very sedentary) to 2.0 or more (for

very physically active individuals). This estimate of

total daily energy expenditure is used by the dietitian

to determine the patient’s initial caloric requirements

and an estimated rate of weight loss, given a specific

reduction in energy intake in the diet.

0013 Summary The entire multidisciplinary assessment

can be an emotional and draining experience for the

patient, who may not have previously talked about

(or even thought about) his or her life in such an

indepth way, and to a team of clinicians. We have

found, however, that only after a comprehensive

evaluation by the multidisciplinary treatment team

can an optimized and individualized treatment plan

be recommended.

Multidisciplinary Treatment

0014 After multidisciplinary evaluations are complete,

treatment can begin. The patient may participate

in individual and/or group sessions with members

of the treatment team. Weekly treatment sessions are

recommended initially (for at least the first month

of treatment), to provide the support and education

necessary for the patient to stabilize his/her eating

behavior and implement the suggested dietary and

physical activity changes. Once weight loss is under

way, less frequent appointments may suffice.

0015 Medical monitoring Ongoing medical manage-

ment, including vital signs, brief review of systems,

discussion of any adverse effects of the diet or weight

loss, and periodic repeated blood tests, is recom-

mended for patients on low-calorie diets (< 1200 cal-

ories per day) and/or those with serious medical

comorbidities. Medication dosage or scheduling (for

example, of orally administered glucose-lowering

agents or insulin) may need to be adjusted as a result

of energy restriction and weight loss.

0016 Behavior modification and psychological treatment

Behavior modification in the treatment of obesity

is a methodology for systematically modifying a pa-

tient’s eating, exercise, or other behaviors that may be

contributing to the obesity. It is typically the psych-

ologist on the treatment team who suggests or imple-

ments behavioral techniques, although these tools

may be useful in all components of treatment. The

six principles used in behavior modification typically

include self-monitoring, stimulus control, contin-

gency management, stress management, cognitive

restructuring, and social support.

0017Self-monitoring is the detailed, daily recording of

food intake (or other behaviors) and the circum-

stances under which the behavior occurs. Food

and exercise diaries (Figure 1) are used to assess the

patient’s eating and activity habits, to increase

the patient’s awareness of his or her own behavior,

and to promote positive behavior change. Patients

may be encouraged to record time of eating episodes,

type and amount of food eaten, feelings of hunger and

satiety, place, context, and/or comments (such as,

‘Out with friends at happy hour’ or ‘Not hungry but

feeling deprived’). These records are reviewed in

treatment sessions, so that specific feedback can be

provided to the patient. Research has consistently

demonstrated that self-monitoring is associated with

improved treatment outcomes, and patients often

report that it is one of the most helpful obesity

management tools.

0018Stimulus control involves identifying the environ-

mental cues associated with unhealthy eating and in-

activity. Modifying these cues involves strategies such

as only eating at the kitchen table and not in front of

the television; keeping tempting, high-calorie foods

out of the house (or at least, out of sight); and laying

out exercise clothes the night before as a reminder to

exercise in the morning. Research has suggested that

obese individuals are more strongly influenced by ex-

ternal cues to eating than are nonobese people. There-

fore, modifying or eliminating these external cues can

reduce eating in response to them. For this reason,

patients are encouraged to ‘turn off all distractions’

while eating, in order to reduce environmental and

behavioral cues to eating, such as watching television,

reading the newspaper, or driving.

0019Contingency management is the use of rewards

for appropriate behavior changes, such as increasing

frequency of exercise or reducing intake of fast

foods. The rewards can be granted by the patient,

the patient’s family, and/or the weight management

center; however, rewards must be of value and re-

inforcing to the patient in order to be effective. At

some weight-loss programs, patients can earn monet-

ary ‘vouchers’ towards treatment sessions and

products for regular attendance and compliance

with treatment recommendations.

0020Stress management involves the use of problem-

solving strategies to reduce or cope with stressful

events. Meditation, relaxation procedures, and regu-

lar exercise are effective techniques to reduce feelings

of stress. However, stress management also involves

helping the patient understand the cause(s) of his/her

stress in order to make the necessary life or environ-

mental changes to prevent ongoing, chronic stress,

which can interfere with weight-loss efforts or

exacerbate the weight problem.

4234 OBESITY/Treatment

0021 Cognitive restructuring techniques are used to

identify and modify a patient’s dysfunctional

attitudes and beliefs about weight regulation and

body image. Examples include the use of affirm-

ations (such as positive self-statements) and visual

imagery (such as seeing oneself eating and exercising

appropriately or visualizing a realistic body size).

Many overweight patients adopt ‘all or none’ or di-

chotomous thinking patterns, which need to be com-

bated with more flexible thoughts such as, ‘Even

though I ate two donuts this morning, the day is not

ruined, and I will recommit to sticking to my diet

plan, starting now!’

0022 The final behavioral principle is social support.

Such support, usually from the patient’s family or

a support group, is used to maintain motivation

and provide reinforcement for appropriate behavior

changes. Facilitated support groups are often an

integral part of comprehensive weight-loss treatment

for these reasons, and they further serve to ‘normal-

ize’ the ups and downs of the treatment process.

0023These six behavioral principles are immensely

useful in helping patients adhere to a healthy diet

and exercise program. However, behavior modifica-

tion alone may not be enough to address all of

the psychological complexities of obesity and associ-

ated eating problems. Many patients seeking weight-

loss treatment are clinically depressed in addition

to being obese. For patients who are introspective

and amenable to therapy, psychotherapy may be

fig0001 Figure 1 Example of a self-monitoring record.

OBESITY/Treatment 4235

recommended, either as part of their weight-loss

program or with a therapist outside the program.

Depressed patients who are not interested in psycho-

therapy, cannot afford it, or are severely depressed

may be prescribed an antidepressant by the physician

on the treatment team or referred to a psychiatrist.

Although depressive symptoms often improve with

weight loss, adherence to treatment may be easier if

the patient is not actively depressed. Individual or

group psychotherapy may also be beneficial to ad-

dress other issues related to obesity, such as low self-

esteem, body image, and relationship problems. Binge

eating or other eating disorders often coexist with

obesity and may require separate treatment by

a specialist.

0024 Nutritional management Nutritional management

of obesity entails an individualized approach, based

on the dietary assessment, within a multidisciplinary

setting whenever possible. Diet prescription for

weight management involves a caloric deficit to

promote weight reduction. For patients with mild to

moderate obesity, a caloric deficit of at most 500–750

calories per day is recommended to promote a 0.5–

0.7 kg weight loss per week. A low-calorie, individu-

alized food-based diet that is either balance-deficit

(reducing the total number of calories while keeping

proportions from carbohydrate, fat, and protein ba-

sically the same as before) or a fat-deficit diet, with

most of the caloric reduction resulting from restric-

tion of fat, can be prescribed. The latter approach

is preferable for Americans, whose typical diet is too

high in fat. Also, a greater volume of food can be eaten

on a diet that emphasizes complex carbohydrates and

reduces fat intake to 20–25% of calories consumed.

In either case, the focus of a calorie- reduced food-

based plan should be on nutritional balance, with

calories distributed appropriately among carbohy-

drates, protein, and fat, based on recommendations

outlined in the US Department of Agriculture Dietary

Guidelines for Americans or similar World Health

Organization guidelines.

0025 The diet must be realistic – that is, based on dietary

modification and practical changes in eating habits.

Nutritional recommendations should be determined

by the patient’s current eating habits, lifestyle, ethni-

city and culture, other coexisting medical conditions,

and potential nutrient–drug interactions. The patient

should be advised to drink at least 1.5–2.0 l of water

daily, unless contraindicated, e.g., by congestive heart

failure, edema, or renal insufficiency. Patients should

also be encouraged by the dietitian to self-monitor

their food intake, which may include measuring por-

tion sizes and recording and calculating calories, fat

grams, and/or carbohydrate grams. If energy intake

is prescribed below 1200 calories per day, daily sup-

plementation is usually indicated to ensure adequate

vitamin and mineral intake.

0026Suggesting gradual changes is helpful in altering

diet composition. Depending on the initial quality

of the patient’s diet, the dietitian may focus on

revamping one meal at a time, so as not to overwhelm

the patient. For example, if a patient’s usual breakfast

consists of biscuits with gravy, bacon, and sausage

from a fast-food restaurant, an alternative of home-

prepared oatmeal, yogurt, and fruit may be sug-

gested. Once the patient has incorporated this

change, the dietitian may then move on to improving

the lunch meal. It is better to recommend dietary

changes that are feasible (and achievable) for a pa-

tient, rather than prescribing a diet that the patient

will reject or not be able to follow. Similarly, reducing

the fat content of milk or meats in stages (e.g., 2%

to 1% to skim milk) gives the patient a chance to

adjust to the new taste before further reducing to a

lower-fat version.

0027Exercise treatment Although regular, moderate

physical activity alone results in limited weight loss

over the long term, it is an essential and high-priority

component of any weight management program.

Regular physical activity is thought to be the most

important predictor of long-term weight mainten-

ance. Research has shown that patients who diet

and exercise regularly are much more likely to

maintain weight loss than those treated with diet

alone. When performed in conjunction with caloric

restriction, regular, moderate physical activity

achieves the following effects: increases 24-h energy

expenditure; maintains (or minimizes loss of) lean

body mass; reduces cardiovascular risk by producing

beneficial changes in the lipid profile; has positive

psychological effects; improves insulin sensitivity;

and may provide other health benefits independent

of weight loss.

0028In determining an appropriate, individualized exer-

cise program, the exercise physiologist and the

patient together should consider a plan that: (1)

fitsinto the patient’s schedule and lifestyle; (2)

considers the patient’s likes/dislikes; (3) makes use

of the patient’s resources; and (4) is based on the

patient’s current level of fitness. The exercise

physiologist should ensure that, before beginning a

fitness program, all patients can recognize and

dealwith abnormal physical responses to physical

activity.

0029Eventually, the exercise goal of any weight

management program should be 30–60 min of

continuous, moderate-intensity physical activity five

to seven times per week. Until a patient can tolerate

4236 OBESITY/Treatment

30 min of continuous activity, several 10-min periods

of physical activity throughout the day can help build

the patient’s endurance while still burning calories.

Additionally, short exercise and rest intervals can be

alternated. The intensity, duration, and frequency of

activity should be progressively increased, according

to the patient’s increasing ability. Patients should be

encouraged to self-monitor their daily physical activ-

ities, including type of activity, time performed, and

duration, so that progress can be appreciated and the

goal reset a bit higher from time to time. The exercise

physiologist may serve as a personal exercise trainer

for those who desire additional motivation and

accountability.

Popular Weight-Loss Approaches

0030 Many overweight and obese individuals do not seek

or have access to the type of multidisciplinary treat-

ment described above, so instead, they turn to

popular or fad diets, commercial weight-loss pro-

grams, and/or self-help groups. These three types of

approaches will be briefly reviewed in the following

section.

Popular Diets

0031 Numerous commercially advertised diets are avail-

able to consumers today that promise quick results

and a ‘magic bullet’ approach to weight reduction.

We believe that it is best to be skeptical, and instill

such skepticism in overweight individuals, about diets

that are not part of a comprehensive approach to

weight management. Many popular diets are based

on very limited menus, because monotony may help

curtail consumption. Any severely reduced-calorie

diet will initially cause diuresis, which makes the

diet seem efficacious at first. This diuresis usually

results in approximately 2–4% loss of body weight

during the first 7–10 days, although most of this

weight will be regained when the period of severe

caloric restriction ends.

0032 Many popular diets are based on the dieter

counting and limiting calories or some other constitu-

ent (such as fat, sugar, carbohydrates), with the end

result that energy intake is decreased. Another type of

popular diet is a fixed-energy-level diet, which limits

intake by controlling portion sizes, menu choice, and

composition. Popular diets of this type include

prepackaged and portion-controlled foods available

in supermarkets or from commercial and nonprofit

weight management programs. Other popular diets

may use an energy-deficit approach (described previ-

ously) or prescribe moderate hypocaloric plans, such

as 1800 calories per day for men and 1200 calories

for women.

0033A current trend in the USA is that of high-protein,

low-carbohydrate plans, such as the Atkins diet,

Sugar Busters, and the Carbohydrate-Lover’s diet (to

name a few). These diets are not nutritionally bal-

anced and have not been scientifically demonstrated

to be effective or healthful in the long term. They

promote the metabolic state of ketosis, resulting in a

large initial diuresis, as described above, which will

be reversed once carbohydrates are reintroduced into

the diet.

Commercial and Self-Help Approaches

0034Self-help and commercial groups have the potential

to offer the personal involvement and comprehensive

approach needed to promote behavior changes

in complex problems such as obesity. This potential,

combined with the large numbers of people who

can be reached, make these groups the most influen-

tial approaches to weight management currently

available. On the negative side, these groups often

generate expectations greater than can be reasonably

achieved, sometimes through misleading advertising.

In addition, evaluations and outcome statistics

of these programs (if existing) have not been made

public.

0035Commercial programs Many commercial (for-

profit) programs provide information on dieting and

nutrition and may include elements of physical activ-

ity, behavioral techniques, the provision of food, and

group support. In the USA, we have seen the recent

emergence of local, commercial weight-loss centers,

run by physicians, in which the primary treatment is

medication that is either prescribed or dispensed at

the center. Often, preprinted diet plans are given to

patients with limited, if any, nutritional or behavioral

counseling.

0036Self-help groups Self-help groups gather people

with weight and/or eating problems and operate at

little or no cost, generally without professional inter-

vention. These groups offer considerable social sup-

port but vary in their philosophy. A group such as

TOPS (Take Off Pounds Sensibly) includes more be-

havioral principles, whereas Overeaters Anonymous

is based on the 12-Step model used in addiction pro-

grams and focuses on ‘compulsive overeating’ as the

core problem.

0037Lack of evaluation It is striking how little is

known about the effectiveness of commercial and

self-help approaches. A few scattered papers have

been published on such groups, but the focus has

been on attrition rates rather than on the weight

OBESITY/Treatment 4237

loss and maintenance of the participants. It is

possible that the lack of evaluation is due to prob-

lems with confidentiality in the self-help groups and

with protecting the financial interests of the

commercial programs. The closed atmosphere that

now surrounds these programs will probably remain

so unless regulatory action forces a scrutiny of

treatment results.

0038 In light of the lack of evaluation of commercial and

self-help programs, and the similar lack of research

on the safety of many popular diets, we recommend

that all self-initiated weight loss attempts be ap-

proved and monitored by the individual’s primary

physician or an expert in weight management, if the

primary physician is not trained or experienced in this

area.

Aggressive Approaches to Weight Loss

0039 More aggressive weight management approaches are

available under medical supervision and are appro-

priate for individuals who are severely overweight

(generally BMI 35) and/or those with serious med-

ical conditions related to their obesity. Obese patients

who have failed multiple weight reduction attempts

through traditional programs may also be considered

for aggressive strategies. Examples of aggressive ap-

proaches include supervised VLCDs, pharmacologic

treatment, and surgery.

Very-Low-Calorie-Diets

0040 A medically supervised VLCD (fewer than 800 cal-

ories per day) may consist of food, commercially

available liquid supplements, or a combination of

the two. The first incarnation of these diets was in

the form of egg- or milk-based protein combined with

water. The use of these severely calorie-restricted diets

in medically unsupervised individuals led to at least

58 highly publicized deaths, often resulting from elec-

trolyte imbalances and sudden cardiac death. How-

ever, with experience and careful patient selection

and monitoring, VLCDs have evolved into compara-

tively safe weight-loss techniques. It is recommended

that patients being considered for VLCDs undergo

a comprehensive medical examination and an ECG.

Absolute contraindications include the presence of

untreated or severe cardiac, hepatic, renal, or throm-

boembolic disease; type 1 diabetes; cancer; and eating

disorders. Weekly medical supervision is recom-

mended while on the VLCD. With full adherence,

weight loss averages 1.1–1.8 kg per week, depending

on body mass and physical activity level. The initial

diuretic phase may be pronounced and accompanied

by symptoms such as lightheadedness, headache,

or fatigue. Later symptoms may include constipa-

tion and cold intolerance. The diet period is followed

by progressive refeeding. Throughout the course

of dieting, education on nutrition, exercise, and

behavior modification will help the patient maintain

his/her weight loss during and beyond the refeeding

phase. For this reason, multidisciplinary treat-

ment is strongly recommended in combination with

the VLCD. Without this education and support,

weight gain will likely occur almost as rapidly as

weight loss.

Pharmacologic Treatment

0041Adjuvant anorectic medications may be useful in

select obese patients (BMI 30 or BMI ¼27–29

with at least one major comorbidity) who have been

unsuccessful in previous coordinated weight-loss

efforts. Commonly used medications in the treatment

of obesity are listed in Table 1. Among the safest and

most effective medications currently available are

phentermine and sibutramine, both centrally active

appetite suppressants.

0042Phentermine is thought to increase the release and

inhibit the reuptake of norepinephrine (noradren-

aline) and dopamine from nerve terminals in the

brain, thereby suppressing feelings of hunger. The

Food and Drug Administration (FDA) has approved

phentermine for short-term use (that is, a few weeks

to 3 months). Sibutramine, a serotonin and norepin-

ephrine reuptake inhibitor, appears to decrease food

intake and may increase energy expenditure as well.

Sibutramine has been approved for use for up to

1 year, to aid in weight loss or maintenance of weight

loss.

0043An entirely different mechanism of action is

employed by the recently FDA-approved agent,

orlistat tetrahydrolipstatin. Orlistat is an inhibitor

of pancreatic lipase; thus, it blocks absorption of

fat, resulting in about 30% of ingested fat being

tbl0001Table 1 Medications currently used for treatment of obesity

and example trade names

Centrally acting anorexic agents

Phentermine (Fastin, Adipex-P, Ionamin)

Sibutramine (Meridia)

Mazindol (Mazanor, Sanorex)

Diethylpropion HCl (Tenuate)

Phenylpropanolamine (Dexatrim, Acutrim, decongestants)

Ephedrine (decongestants, herbal weight-loss supplements)

Locally acting agents

Orlistat tetrahydrolipstatin (Xenical)

HCl, hydrochloride.

4238 OBESITY/Treatment

excreted in the stools, with predictable side-effects.

Its efficacy in weight loss is probably not only

due to the decreased absorption of calories, but

also to the Antabuse-like effect when a high-fat eating

episode occurs. Orlistat is to be used in obese adults

three times per day before meals and has been shown

in studies of up to 2 years’ duration to improve weight

loss and maintenance. Because the malabsorption

of fat induced by orlistat also causes malabsorption

of fat-soluble vitamins, use of a vitamin supplement

is recommended.

0044 Incremental weight loss in controlled trials of an-

orexic agents tends to be in the range of 0.2 kg per

week greater than placebo. This is a definite benefit,

but the risks of drug therapy (as illustrated by the fen-

phen controversy) must be carefully balanced against

the benefits. There is the potential for medications to

be prescribed inappropriately, to individuals who do

not meet criteria for use or beyond the duration of

continued efficacy. Physiologic or behavioral toler-

ance to these medications, resulting in decreased

effects, may occur over time, and some are not

recommended, and have not been studied, for longer

than 3 months. At best, antiobesity agents may pro-

vide certain obese patients with a ‘jump-start’ to

weight loss, or they may be used to improve dietary

adherence during a particularly difficult time in the

course of treatment.

Surgery

0045 Surgical treatment of obesity may be considered only

in carefully selected patients who meet the following

criteria: (1) a very high medical risk exists (BMI 40

or BMI ¼35–39 with life-threatening or disabling

comorbidities); (2) obesity has been present for at

least 5 years; (3) no history of or current untreated

alcoholism, drug abuse, or major psychiatric disorder

is noted; and (4) the patient is between 18 and 65

years of age. In addition, patients should have failed

previous attempts at medically supervised weight

reduction and should have realistic expectations

about the long-term outcome achievable with sur-

gery. A multidisciplinary team approach to screening

patients preoperatively, including evaluation with the

surgeon, a dietitian, a psychologist, and the patient’s

primary physician, is critical to the patient’s long-

term success.

0046 Two proven surgical options are available for

the treatment of morbid obesity: purely restrictive

operations such as the vertical banded gastroplasty

(gastric stapling), and gastric bypass operations such

as the Roux-en-Y gastric bypass. These procedures

primarily involve either the mechanical restriction of

caloric intake by creating a small gastric reservoir, or

the induction of malabsorption by bypassing variable

lengths of the small intestine. The vertical banded

gastroplasty (Figure 2) achieves weight loss by creat-

ing a small pouch with a narrowed outlet in the

stomach by using a band of synthetic material. With

the gastric bypass procedure (Figure 3), a small pouch

is created of 20–30 ml, which limits oral intake, and a

moderate degree of malabsorption is created by a

Roux-en-Y loop of bowel anastomosed to this small

gastric remnant.

0047The Roux-en-Y gastric bypass produces more sub-

stantial weight loss than vertical banded gastroplasty

and may have longer-lasting effects. The gastric

bypass results in weight loss averaging 50–60% of

excess body weight, with good weight control docu-

mented for up to 10 years. This procedure is not

without risks, including post surgical complications,

food intolerance, nutritional deficiencies, extreme

psychiatric distress, and even death. However, in the

majority of patients, obesity-related comorbidities,

such as diabetes and hypertension, are either reversed

or prevented after obesity surgery, as long as weight

loss is maintained.

Maintenance of Weight Loss

0048Maintaining weight loss seems to be inherently

more difficult than losing weight, particularly for

Esophagus

Staples

Stomach

pouch

Band

Small

intestine

fig0002Figure 2 Vertical banded gastroplasty. A vertical staple line

reduces the size and accommodation of the stomach. Mesh

banding of the distal portion of the newly created gastric pouch

slows the exit of food, leading to early satiety. Reproduced with

permission from Schaefer DC and Cheskin LC (1998) Update on

obesity treatment. Gastroenterology 6(2): 136–145.

OBESITY/Treatment 4239

individuals who used or were treated with caloric

restriction. Unfortunately, the long-term success rate

for all weight-loss methods (excluding surgery), de-

fined as losing weight and keeping the majority of it

off for at least 5 years, is low – perhaps 5–15%. Even

after the most state-of-the-art, medically monitored

comprehensive treatment, it is likely that patients

will gradually return to their baseline weight within

3–5 years after treatment termination. Given this

very high relapse rate, obesity can be considered a

chronic condition, much like cigarette smoking

or other substance abuse. As such, only the continu-

ous-care model of management, which views obesity

as a chronic disease requiring continuous support

or contact after the end of formal treatment, has

been found to produce significant maintenance

of weight loss.

0049 It is probable that some form of continuous or

punctuated long-term care will be necessary for

many (if not all) obese patients to maintain the diet-

ary and lifestyle changes that produced their weight

loss. With ongoing support from a physician or other

health care providers, patients will be better able to

maintain their changes in eating and activity behavior

and the resultant weight loss. Regrettably, optimal

strategies for weight maintenance are in a state of

evolution and represent the key limitation of our

current treatment of this highly prevalent, medically

hazardous, and chronic condition. Research has iden-

tified continued program contact (e.g. monthly),

regular physical activity, nutritional sophistication,

and self-monitoring as four predictors of weight

maintenance. It not surprising that the strategies help-

ful in promoting weight loss, such as self-monitoring,

physical activity, regular weigh-ins, and attendance at

a multidisciplinary program, will be the same strat-

egies necessary for long-term maintenance of weight

loss.

See also: Behavioral (Behavioural) Effects of Diet;

Body Composition; Bulimia Nervosa; Exercise:

Muscle; Metabolic Requirements; Fat Substitutes: Use of

Fat-replaced Foods in Reducing Fat and Energy Intake;

Hunger; Metabolic Rate; Nutrition Education;

Nutritional Assessment: Importance of Measuring

Nutritional Status; Obesity: Etiology and Diagnosis; Fat

Distribution; Epidemiology; Satiety and Appetite: Food,

Nutrition, and Appetite; Slimming: Slimming Diets;

Metabolic Conseqences of Slimming Diets and Weight

Maintenance

Further Reading

AACE/ACE Obesity Task Force (1998) AACE/ACE pos-

ition statement on the prevention, diagnosis, and treat-

ment of obesity (1998 revision). Endocrine Practice 4(5):

297–330.

Bray GA (1998) Contemporary Diagnosis and Manage-

ment of Obesity. Newtown, PA: Handbooks in Health

Care.

Brownell KD and Fairburn CG (1995) Eating Disorders

and Obesity: A Comprehensive Handbook. New York:

Guilford Press.

Cheskin LJ (1997) Losing Weight for Good: Developing

Your Personal Plan of Action. Baltimore, MD: Johns

hopkins University Press.

Foreyt JP and Poston WSC (1998) What is the role of

cognitive-behavior therapy in patient management?

Obesity Research 6 (suppl. 1): 18S–22S.

National Institutes of Health Consensus Development

Panel (1991) Gastrointestinal surgery for severe obesity.

Annals of Internal Medicine 115: 956–961.

Perri MG, Nezu AM and Viegener BJ (1992) Improving

the Long-term Management of Obesity: Theory,

Research, and Clinical Guidelines. New York: John

Wiley.

Schaefer DC and Cheskin LJ (1998) Update on obesity

treatment. Gastroenterologist 6(2): 136–145.

Thomas PR (ed.) (1995) Weighing the Options: Criteria for

Evaluating Weight-Management Programs. Washing-

ton, DC: National Academy Press.

Wadden TA and Van Itallie TB (1992) Treatment of

the Seriously Obese Patient. New York: Guilford

Press.

Small

intestine

Stomach

pouch

Esophagus

Staples

Unused

portion of

stomach

Bypassed

part of small

intestine

fig0003 Figure 3 Gastric bypass. A horizontal staple line reduces the

size and accommodation of the stomach. A jejunal limb is

attached to the new gastric pouch, thus allowing bypass of the

duodenum. Reproduced with permission from Schaefer DC and

Cheskin LC (1998) Update on obesity treatment. Gastroenterology

6(2): 136–145.

4240 OBESITY/Treatment

Epidemiology

N E Sherwood and M Story, University of Minnesota,

Minneapolis, MN, USA

Introduction

0001 Obesity is a major public health problem in the USA.

The dramatic increase in the prevalence of obesity

over the last few decades has raised concerns about

associated health risks for children, adolescents,

and adults. Obesity is considered the second leading

cause of preventable death in the USA. Recent data

suggest that the estimated number of annual deaths

in the USA due to obesity approaches 300 000. A

continuation of current trends could lead to fur-

ther increases in the number of people affected by

obesity-related health conditions and premature

mortality. Prominent among the health risks associ-

ated with obesity are hypertension, type 2 diabetes

mellitus, dyslipidemia, stroke, gallbladder disease,

osteoarthritis, sleep apnea, respiratory problems,

and certain cancers (e.g., endometrial, breast, pro-

state, and colon). Obesity is also associated with

psychosocial problems such as binge-eating disorder

and depression. Furthermore, individuals who are

obese are adversely impacted by social bias and

discrimination.

0002 As the prevalence of obesity has been rising, the

economic burden of obesity has been a topic of con-

siderable discussion. The economic costs of obesity

have been categorized into three areas, the cost to

individuals because of the impact of obesity on

health, costs to society due to lost productivity and

premature mortality associated with obesity, and

costs to individuals and service providers in treating

obesity. Recent estimates suggest that obesity-related

mortality may account for 7% of US health care

costs. Medical care costs alone attributable to obesity

in the US were estimated to toal almost $46 billion

in 1990. Although no study to date has taken into

account the entire range of costs associated with

obesity, estimates of the economic burden are as

high as $100 billion per year.

0003 Monitoring the prevalence of obesity and associ-

ated health behaviors is critical for understanding

and documenting the scope of the problem. The

goal of this chapter is to review definitions of

overweight and obesity in adults and children, pre-

sent available data regarding the epidemiology of

obesity and related risk factors, and discuss impli-

cations for future public health research and inter-

vention.

Definitions of Overweight and Obesity

0004The terms obesity and overweight are often used

interchangeably, but they are distinct conditions.

Obesity refers to excess adipose tissue, whereas over-

weight refers to excess weight for height. Because it is

difficult to obtain direct measures of obesity and since

body weight tends to be highly correlated with adi-

posity, weight-for-height measures are generally used

to classify overweight and obesity in adults and

youths.

Adults

0005Definitions of obesity and overweight have varied

over time and in different countries. In the USA,

many studies have used the 1959 or 1983 Metropol-

itan Life Insurance tables of desirable weights for

heights and defined overweight as a weight exceeding

the midpoint of these standards by a certain percent-

age. In 1985, a NIH Consensus Conference en-

dorsed the use of body mass index (BMI; kg m

2

)

and adopted the 85th percentile of BMI from the

second National Health and Nutrition Examination

Survey (NHANES II) as the standard for defining

overweight. The 85th percentile corresponded well

to approximately 20% overweight according the

1983 Metropolitan Life tables. Using this standard,

overweight was defined as BMI 27.8 for men and

27.3 for women. In 1995, a World Health Organ-

ization (WHO) expert committee recommended an

alternative classification system for overweight and

obesity; overweight was defined as a BMI of 25–

29.9 kg m

2

and obesity as a BMI 30 kg m

2

. Al-

though the previous definition of overweight in the

US used a cut-off of about 27 kg m

2

, epidemi-

ological data show increases in mortality with BMIs

above 25 kg m

2

. The category of obesity is further

subdivided into three classes: obese class I (BMI 30–

34.9), obese class II (BMI 35.0–39.9), and obese class

III (BMI 40).

0006BMI has been accepted by numerous groups as the

most practical and valid screening tool for assessing

weight status in individuals and the most useful popu-

lation-level measure of overweight and obesity. BMI

provides meaningful prevalence estimates within and

between populations and is useful for identifying

individuals and groups at increased health risk and

for evaluating the efficacy of obesity interventions.

However, it is important to recognize that BMI does

not provide information on body fat or body-fat dis-

tribution. Body-fat distribution has been identified as

an independent predictor of health risk. Individuals

with excess abdominal fat are at increased risk of

negative health consequences of obesity. In adults,

OBESITY/Epidemiology 4241

the waist-to-hip ratio, or waist circumference, is often

used as a marker of intraabdominal adipose tissue.

Children and Adolescents

0007 Defining overweight or obesity in children and

adolescents is complicated by the normal pro-

cesses of growth, pubertal development, and body-

composition changes. No standard definition exists

for child or adolescent obesity. Classifications that

have been used include weight-for-height percentiles,

relative weight, percent of ideal body weight, skinfold

measures, and BMI. BMI is currently the most

accepted and widely used measure. For adults, BMI

criteria have been based on mortality or mortality

outcome research, but no risk-based criteria have

been established for youths, as it is difficult to link

youth weight status to chronic disease outcomes.

Adult BMI criteria also utilize a single cut-off value

for both sexes and all ages, which is inappropriate for

children and adolescents who are experiencing

growth and body-composition changes. Because

BMI changes dramatically with age during childhood

and adolescence, BMI needs to be assessed using age-

specific reference curves. Gender-specific values are

also needed for adolescents because of differences in

body composition and timing of puberty. During

puberty, males increase their lean body mass and

decrease the amount of body fat, whereas girls experi-

ence rapid fat accretion.

0008 The release of the revised National Center

for Health Statistics (NCHS) and the Centers for

Disease Control (CDC) growth charts incorporating

smoothed gender- and age-specific BMI percentiles

based on data from National Health Examination

Survey (NHES) and NHANES will provide a useful

reference for describing weight status in children and

adolescents. It has been suggested by US expert panels

that for clinical evaluation of obesity and epidemio-

logic application, overweight in youths should be

defined as a BMI greater than the 95th percentile for

age using national reference population data. Youths

between the 85th and 95th percentile are considered

at risk of becoming overweight.

Prevalence of Obesity: National Trends

Adults

0009 Comprehensive data of trends in the prevalence of

obesity provided by national surveys (NHES I

(1960–1962); NHANES I (1971–1974); NHANES

II (1976–1980); NHANES III (1988–1994)) show

that the percentage of obese persons has increased

over time. Although there was a small increase in

the estimated prevalence of obesity across the first

three periods (1960–1980), a much larger increase

was observed between the third and the fourth

surveys. The percentage of individuals classified as

obese increased from 15% in NHANESII to 23% in

NHANES III. An additional 33% of US adults in

NHANES III were classified as overweight according

to the BMI > 25.0 standard. According to these data,

an estimated 97.1 million adults (55% of US adults)

are classified as overweight.

0010Data from the Behavioral Risk Factor Surveillance

System (BRFSS) also show that the prevalence of

obesity has increased in recent years. The BRFSS is a

cross-sectional telephone survey of noninstitutiona-

lized adults aged 18 and older conducted by the

Centers for Disease Control and Prevention and state

health departments. Data from the BRFSS indicate

that the prevalence of obesity increased from 12% in

1991 to 18% in 1998. The prevalence of obesity in-

creased across both genders, all socio-demographic

groups and in all states. These data are derived from

self-reports of individuals; therefore, true rates of over-

weight and obesity are likely underestimated since

individuals tend to underreport their body weight.

Children and Adolescents

0011Regardless of the method used to classify over-

weight or obesity, studies have shown high prevalence

estimates among children and adolescents, and that

rates have increased dramatically since the mid-1960s

and continue to rise. NHANES data indicate that the

prevalence of overweight (BMI at or above the 95th

percentile) among youths doubled from 1976–1980

to 1988–1994, increasing from 8 to 14% for 6–11

year olds and from 6 to 12% for 12–17 year olds.

Currently, about 11% of US children and adolescents

are overweight, and an additional 14% have a BMI

between the 85th and 95th percentiles, indicating that

they are at risk for becoming overweight.

Gender Differences in Obesity

0012Data suggest that the prevalence of obesity is increas-

ing across all populations in the USA, but epidemi-

ological data show that certain subgroups of

individuals are at a particularly high risk of obesity.

Although the prevalence of obesity has increased over

time in both men and women, the prevalence of over-

weight has remained relatively stable. Data show that

men have higher rates of overweight compared with

women, but women have higher rates of obesity than

men. A major contributor to the high rates of obesity

in US adults is weight gain with age. About two-thirds

of obese adults became obese in adulthood. Between

the ages of 20 and 50 years, weight gain tends to

4242 OBESITY/Epidemiology

occur at a rate of 0.45–0.91 kg per year, and major

weight gain is most likely to occur between the ages of

25 and 34 among both men and women. Prospective

epidemiological data also show that women in the US

appear to be at twice the risk of major weight gain

as men. The prevalence of overweight and obesity

increases with age across both sexes, peaking around

the 50–59-year-old age range. After age 70, the preva-

lence of obesity is lower in adult men and women.

This lower prevalence may be due to both obesity-

related mortality and decreases in BMI with age.

0013 Among children and adolescents, national data

show few gender differences in obesity rates. Males

tend to have slightly higher rates of overweight com-

pared with females (e.g., 15% for males compared

with 14% for females).

Racial/Ethnic Differences in Obesity

0014 Significant racial/ethnic differences in the prevalence

of overweight and obesity have also been observed.

The most recent NHANES III data show that among

women, African American and Hispanic women are

at highest risk, with about two-thirds of women in

these ethnic groups meeting BMI criteria for over-

weight or obesity. Ethnic specific data from studies

such as Hispanic HANES (HHANES), which includes

Mexican Americans, Cuban Americans, and Puerto

Rican Americans, and smaller studies of American

Indians and Alaskan Natives, show high rates of

overweight and obesity in these populations. In con-

trast, ethnic-specific data show that Asian American

women have the lowest rates of overweight and

obesity. Among men, fewer ethnic differences in over-

weight and obesity have been observed. According to

NHANES III data, Hispanic men are at highest risk of

overweight and obesity compared with non-Hispanic

white men and African American men. According to

data from the BRFSS, the prevalence of obesity in

Hispanic men almost doubled over the last decade

(10% in 1991; 18% in 1997). Data from smaller

studies of American Indian and Alaskan Native men

also show elevated rates of overweight and obesity

compared with all-race data in US men.

0015 As with adults, differences in overweight preva-

lence by race and ethnicity have been observed

among children and adolescents. In NHANES III,

the overweight prevalence among youths was consid-

erably higher for male and female Hispanics, and

African American girls compared with whites. For

example, among 6–11 year olds, 16% of black girls,

14% of Hispanic girls, and 9% of white girls were

overweight. Among males aged 6–11, 17% of His-

panic boys were overweight, compared with 10% of

white and 12% of black boys. Other studies have

shown excessively high prevalence estimates of

obesity in American Indian youth. A recent survey

of over 12 000 American Indian youths aged 5–17

years of age in the Northern Plains area found that

22% of the males and 18% of the females were

overweight (BMI > 95th percentile).

Socio-economic Differences in Obesity

0016An inverse relationship between socio-economic

status and obesity has been observed in the USA and

is particularly pronounced for women. Data from

NHANES III show that collapsing across all races,

women with lower incomes are more likely to be

overweight or obese compared with those with higher

incomes. Examination of NHANES III all-race data

for men shows that the prevalence of overweight does

not vary across income groups. The relationship

between socio-economic status and obesity, however,

appears to vary across ethnic groups and according to

gender. There is a strong inverse relationship between

income and weight status among nonHispanic White

women and a moderate inverse relationship between

income and weight status among Hispanic American

women. However, among African American women,

weight status and income are only weakly associated.

A similar trend has been observed in other studies.

Although nonHispanic white men did not show any

difference in weight status across income groups,

examination of similar data in men shows that there

is a positive relationship between income and obesity

for Hispanic American and African American men.

0017Compared with adults, studies with children have

shown a weak and less consistent relationship

between SES and overweight. In NHANES III data,

there was an inverse relationship between SES and

overweight only for white adolescents. Overweight

prevalence was not related to family income in

African American or Hispanic youths.

Persistence of Childhood Obesity

0018Whether childhood-onset obesity leads to an in-

creased likelihood of obesity in later life is an import-

ant issue with clinical implications. The likelihood of

persistence of obesity from childhood to adulthood is

related to the degree and duration of obesity, family

adiposity, and age of the child. The likelihood of an

overweight infant becoming an overweight adoles-

cent or adult is small. Less than 15% of overweight

infants and only about 25% of overweight preschool

children will remain overweight into adulthood.

Obesity is more likely to persist if it is present during

the adolescent years. In general, the later into adoles-

cence overweight persists, the severity of the obesity

OBESITY/Epidemiology 4243