nieman dc. exercise testing and prescription: a health-related approach. 6/e. copyright ©2007...

Nieman DC. Exercise Testing and Prescription: A Health-Related Approach. 6/e. Copyright ©2007 McGraw-Hill Higher Education. All rights reserved.

Chapter 13Obesity


How can an individual know if they are overweight/overfat? How can an individual know if they are overweight/overfat? There is a wide range of options, and a large industry has There is a wide range of options, and a large industry has

developed in body composition analysis.developed in body composition analysis.


How To Estimate Obesity

Obesity can be estimated by using a mathematical formula called the body mass index (BMI) - weight in kilograms divided by height in meters squared (BMI = kg/m2). A BMI of 18.5 to 24.9 is considered a "normal" weight.

A BMI of 25 to 29.9 is considered overweight

A BMI of 30 or above is considered obese.

Obesity threshold weights for given heights


Obesity/Overweight Prevalence

Obesity affects about 3 in 10 adults (compared to Healthy People 2010 goal of 15%), with the highest rates among the poor and minority groups (Figure 13.2).65% overweight/obese (Figure 13.3).Compared to 1960, average adult now weighs 24 pounds more (males = 190 pounds, 69 inches, BMI 28; females = 163 pounds, 64 inches, BMI 28) and the average teenager 15 pounds more.Figure 13.4 shows dramatic increase in obesity prevalence on a state-by-state basis.Among children and adolescents, 16% is rated as overweight, up substantially from the 1960s (Figure 13.5)


48.8

27.8

38

27.8

30.7

28

33.2

27.5

30.4

0 10 20 30 40 50 60

Black females

Black males

Mexican-American females

Mexican-American males

White females

White males

All females

All males

All adults

Prevalence of Obesity (BMI 30+)

Figure 13.2Healthy People 2010 Goal


13.3

14.6

15.1

23.3

31.1

44.8

47.7

47.4

56

65.2

51.2

48.8

49.6

41.7

32.9

0 10 20 30 40 50 60 70

1960-62

1971-74

1976-80

1988-94

1999-02

Percent of Population (20 years of age and older)

Obese Overweight or obese Healthy weight

Figure 13.3


19961991

Obesity Trends* Among U.S. AdultsBRFSS, 1991, 1996, 2004

(*BMI 30, or about 30 lbs overweight for 5’4” person)

No Data <10% 10%–14% 15%–19% 20%–24% ≥25%

2004


Figure 13.5

4.6

6.1

5

10.5

16

4.2

4

6.5

11.4

16

0 5 10 15 20

1963-70

1971-74

1976-80

1988-94

1999-02

Prevalence of overweight

12-19 yrs old 6-11 yrs old


Health Risks of Obesity

A psychological burdenIncreased high blood pressure (Fig 13.6)Dyslipidemia (high cholesterol, triglycerides, LDL-C, low HDL-C (Fig 13.7)Increased risk of gallstones (Fig 13.8)Increased osteoarthritis (Fig 13.9)Increased diabetes (type 2) (Chapter 12, Figs 12.6-12.8)Increased cancer (colon, rectum, prostate, pancreas, liver, kidney, breast, uterus, ovaries, gallbladder, bile ducts) (Chapter 11, Figs 11.6, 11.19, 11.24)Increased mortality and early death (Figs 13.10, 13.11)Increased heart disease and stroke (Figs 13.12, 13.13)


Fig. 13.14 Health risks are worst for androids (waist circumference >35 inches in women, and >40 inches in men)


What Factors Best Explain The Obesity Epidemic In America?

1.

2. 3.


Genetic and Parental Influences

Dr. Mayer, 1965: 80% of offspring of 2 obese parents become obese, 40% with one, and 14% with none. Parental obesity predicts obesity in their offspring, especially when present during the first 10 years of life (Fig 13.18). More than 80% of obese adolescents remain obese as adults (Fig 13.20).Twin studies show that identical twins reared apart have BMIs as close as when reared together.Adults adopted before age 1 have BMIs most similar to biologic parents.Inheritance accounts for 25% of variance in fatness, with lifestyle/environment 45%. See figure 13.19). Subsequent research suggests 25-40% of variance in obesity has genetic basis.Some people are obesity prone because of their genes and must exercise more and eat less than others to achieve desirable weight.


Genetics? Parental influences? One-third of preschoolers become obese as adults, but 80% of

teenagers end up obese as adults (Fig 13.20).

Prev Med 22:167-177, 1993.


High Energy Intake

Do obese people eat more than the nonobese? Older studies used 3-7 day food records, and data suggested energy intake was similar between obese and nonobese.However, obese people tend to underestimate intake by 20-50% (Figure 13.21).Use of respiratory chambers and doubly labeled water show that obese people both expend and ingest more energy (Figure 13.22).


Most obese people are in self-denial. This study showed that obese subjects underestimate food intake by 50% and

overestimate physical activity by 33% (Fig.13.21).


High Energy Intake

When dietary fat intake is high, most adults and children tend to gain weight easily and quickly.

Obese compared to lean people tend to choose high-fat and energy-rich foods more often.

High fat foods are more palatable, prompting people to take in more energy (Figs 13.23 to 13.25).


Low Energy Expenditure

Humans expend energy in 3 ways (Figure 13.26).The resting metabolic rate is directly related to body weight (high in the obese, lower in the lean), and parallels changes in weight (Table 13.1, Fig 13.27).Regular physical activity is related to a reduced risk of body weight gain (Figs 13.28, 13.29).Physical activity is significantly lower in obese people (Fig 13.30, 13.31; Table 13.2). The thermic effect of food (10%) is slightly lower in the obese (Figs 13.32, 13.33).


Daily Energy Expenditure

Fig. 13.26 The largest number of calories expended by most people (except for athletes during heavy training) is from the resting metabolic rate (RMR). Am J Clin Nutr 55:242S-s45S, 1992.

RMR67%

Activity23%

TEF10%


Resting Metabolic Rate (RMR)Description

The basal metabolic rate (BMR) represents the energy needed to support the basic cost of living, including the metabolic activities of cells and tissues, blood circulation, respiration, and gastrointestinal and kidney functions.


Energy Expenditure and Body Mass Change

Fig. 13.27 The resting metabolic rate is directly related to body weight (higher in the obese, lower in the lean), and parallels changes in weight. N Engl J Med 332:621-628, 1995

500

- 25

- 300

- 400 - 200 0 200 400 600

Energy Expenditure Change (kcal/day)

10% weight loss

Back to initial weight

10% weight gain


Table 13.1 RMR Estimation Through Equations

BMR prediction equations have been developed using easily and accurately measurable variables such as age, height, and body weight. The Food and Nutrition Board of the Institute of Medicine recently developed these equations for estimating BMR in adults:

Men: BMR (kcal/day) = 293 - (3.8 x age) + (456.4 x height) + (10.12 x weight)Women: BMR (kcal/day) = 247 - (2.67 x age) + (401.5 x height) + (8.6 x weight)

– [Age is in years, height is in meters, and weight is in kilograms].

Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients). Washington, D.C.: The National Academies Press, 2002.


Equation Example40 yr old woman, 65 inches, 140 pounds

Women: 65 inches x 0.0254 = 1.65 meters

140 pounds x 0.4536 = 63.5 kg

BMR (kcal/day) = 247 - (2.67 x age) + (401.5 x height) + (8.6 x weight)

BMR (kcal/day) = 247 - (2.67 x 40 yr) + (401.5 x 1.65 m) + (8.6 x 63.5 kg) = 1,349

Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients). Washington, D.C.: The National Academies Press, 2002.


47.5

38

28.5

19

9.5

05

101520253035404550

No

n-R

MR

En

erg

y E

xp

en

ditu

re

(kcal/k

g/d

ay)

Lean Normal Above Desired Obese Very Obese

Body Fat Classification

Body Fatness and Energy Expenditure In 300 Subjects (Doubly Labeled Water Method)

Physical activity decreases in direct relationship to

the degree of obesity (Fig. 13.31).

Am J Clin Nutr 60:676-681, 1994


Figure 13.32


Treatment of Obesity Is Challenging

Four in 10 U.S. adults at any given time are trying to lose weight (Fig. 13.34).

Among adults trying to lose weight, only one in five follow 2 key recommendations: eat fewer calories and increase physical activity.

Many obese people will not stay in treatment, and of those who do, most will not achieve ideal weight. Of those who lose weight, most will regain it (Fig. 13.35).

Regular exercise is a marker of long-term success in maintaining weight loss (Fig. 13.36, Box 13.2).


Figure 13.35

-29

-10

2

-29

-15

6

-37

-23

6

-40

-35

-30

-25

-20

-15

-10

-5

0

5

10

Weig

ht L

oss/G

ain

(P

ou

nd

s)

VLCD Alone Behavior Therapy Both

Type of Weight-Loss Program

Maintenance of Weight Loss Over 5 Years After Treatment

End of Therapy 1 year later 5 years later

Int J Obesity 13(suppl 2):39-49, 1989.


Conservative Treatment Guidelines

Obesity should be treated as a chronic condition, not an acute illness.

Incorporate change in diet, increase in physical activity, and change in behavior.

Aim for about 0.5-2 pounds of weight loss a week.

Each pound of fat = 3,500 calories.


How to Lose Weight: The NHLBI Obesity Education Initiative (Box 13.3)

In 1998, the first federal guidelines for the treatment of overweight and obesity in adults were released by the National Heart, Lung, and Blood Institute (NHLBI) as a part of their nationwide Obesity Education Initiative. Key diet recommendations from this initiative include the following:

The initial goal of a weight loss regimen should be to reduce body weight by about 10%. With success, further weight loss can be attempted, if needed.Weight loss should be about 1 to 2 pounds per week for a period of 6 months, with additional plans based on the amount of weight loss. Seek to create a deficit of 500 to 1,000 calories per day through a combination of decreased caloric intake and increased physical activity.


How to Lose Weight: The NHLBI Obesity Education Initiative (Box 13.3) (Cont.)

• Reducing dietary fat intake is a practical way to reduce calories. But reducing dietary fat alone without reducing calories is not sufficient for weight loss.

• Each pound of body fat represents about 3,500 calories. To follow the NHLBI for weight loss, one must expend 500 to 1000 calories more than the amount taken in through the diet. This can be accomplished by increasing energy expenditure 200-400 calories a day through physical activity, and reducing dietary fat intake by 300-600 calories. Each tablespoon of fat represents about 100 calories, so an emphasis on low-fat dairy products and lean meats, and a low intake of visible fats is the easiest way to reduce caloric intake without reducing the volume of food eaten.


How to Lose Weight: The NHLBI Obesity Education Initiative (Box 13.3) (Cont.)

The NHLBI recommends this diet for weight loss:Eat 500-1,000 calories a day below usual intake.Keep total dietary fat intake below 30% of calories, and carbohydrate at 55% or more of total calories.Emphasize a heart-healthy diet by keeping saturated fats under 10% of total calories, cholesterol under 300 mg per day, and sodium less than 2,400 mg per day.Choose foods high in dietary fiber (20-30 grams per day).


The NHLBI Obesity Education Initiative promotes weight loss surgery is an option for weight reduction in patients with clinically severe obesity, defined as a BMI≥40, or a BMI≥35 with comorbid conditions. (See Box 13.5).

Weight loss surgery should be reserved for clinically severe obese patients in whom other methods of treatment have failed. See Figure 13.37 for surgery options.

Gastric Reduction Surgery


Weight Loss Drugs

The NHLBI Obesity Education Initiative promotes FDA-approved weight loss drugs for long-term use as an adjunct to diet and

physical activity for patients with a BMI≥30 and without concomitant obesity-related risk factors or disease. (See Box 13.5).

Drug therapy may also be useful for patients with a BMI≥27 who also have concomitant obesity-related risk factors or diseases.

In general, drugs should be used only as part of a comprehensive program that includes behavior therapy, diet, and physical activity. Appropriate monitoring for side effects must be continued while drugs are part of the regimen. Since obesity is a chronic disease, the short-term use of drugs is not helpful. The health professional should include drugs only in the context of a long-term treatment strategy.


The VLCD provides 400-800 Calories/day; long-term success is poor (see Figure 13.39).The NHLBI recommends that VLDCs not be used routinely for weight-loss therapy:

Energy deficits are too great.Nutritional inadequacies will occur without supplements.Moderate energy restriction is just as effective over the long-term.Rapid weight reduction does not promote gradual change in eating behavior.Linked to increased risk of gallstones.Require special monitoring.

Very Low Calorie Diets


Misconceptions Regarding the Role of Exercise In Weight Loss (Box 13.9)

Accelerates weight loss significantly when combined with a reducing diet (Figs 13.40 to 13.43).

Causes the RMR to stay elevated for a long time after the bout, burning extra calories (Figs 13.44, 13.45).

Counters the diet-induced decrease in RMR (Figs 13.46, 13.47, 13.48).

Counters the diet-induced decrease in fat- free mass (Fig 13.46, 13.49, 13.50).


Misconception #1: Aerobic Exercise Accelerates Weight Loss Significantly When Combined With A

Reducing Diet

Some obese people have been led to believe that if they start brisk walking 2-3 miles/day (or workout for 30-45 min/day) significant

amounts of body weight will be lost quickly. This is not true.

-1.8 -2.2

-17.2 -17.8

-18

-16

-14

-12

-10

-8

-6

-4

-2

0

Weig

ht L

oss (P

ou

nd

s)

Controls Walking Diet Diet and Walking

Group Status (Diet 1,300 kcal/day); Exercise (5-45 min walk/wk)

Body Weight Changes Over 12-Weeks With Diet And/Or Exercise

Int J Sports Nutr 8:213-222, 1998.

Fig. 13.40


Why? The net energy expenditure of exercise is small (only about 135 kcal per 3-mile walk). To be accurate, the RMR and potential informal activity

calories must be subtracted out.

Fig. 13.43


Misconception #2: Exercise Causes the Resting Metabolic Rate to Stay Elevated for a Long Time after the Bout, Burning Extra Calories

The truth is that the energy expended after aerobic exercise is small unless a great amount of high intensity exercise is engaged in.

Moderate intensity exercise for 30 min increases the RMR for only 20-30 min, burning 10-20 extra calories.

High intensity exercise for 30 min increases the RMR for 35-45 min, burning 15-30 extra calories.

Thus when the obese individual walks for 20-30 min, about 10 extra calories will be burned afterwards, hardly enough to be meaningful.


-5-15

-25

90

75

50

10

25

50

-40

-20

0

20

40

60

80

100

1200-1500 400-800 FastingEnergy Intake (Kcal/day)

Per

cen

tag

eRMR Fat Mass Fat-Free Mass

Fig. 13.46 During caloric restriction (dieting), the resting metabolic rate drops 5-30%, and the fat-free mass drops 10-50% (with degree of

decrease depending on the severity of the energy decrease).


Misconception #3: Exercise counters the diet-induced decrease in RMR.

Most studies have found that exercise during dieting does not counter the decrease in RMR and fat-free mass.

65 obese, 8 wk, formula diet at 70% RMR; aerobics 3/wk, leg/arm cycling; weights 3x/wk, 3x6, 8 stations.Am J Clin Nutr 66:557-563, 1997.

-88

-148

-127

-160

-140

-120

-100

-80

-60

-40

-20

0

Diet Alone Aerobics & Diet Weights & Diet

Ch

an

ge in

RM

R (

kcal)

Fig. 13.47


-10.3 -10.6 -10.3

-9

-12

-10

-8

-6

-4

-2

0

Diet Alone Weights & Diet

Perc

en

t D

ecre

ase in

RM

R

Fig. 13.48 90 day study of 69 obese females, all on 520 kcal/day formula. Aerobics = 4 d/wk, 20 min progressing to 60 min/session; weights = 4 d/wk, 2-3 sets, 6-8 reps.

Am J Clin Nutr 54:56-61, 1991.


Practical Conclusions

To sum up, individuals adopting a moderate exercise program to lose weight should not count on a revved up metabolism to burn a

significant amount of extra calories beyond that linked to the exercise itself.


2005 USDA Dietary Guidelines

■ To reduce the risk of chronic disease in adulthood: Engage in at least 30 min of moderate-intensity physical activity, above usual activity, at work or home on most days of the week.■ To help manage body weight and prevent gradual, unhealthy body weight gain in adulthood: Engage in approximately 60 min of moderate- to vigorous-intensity activity on most days while not exceeding caloric intake requirements.■ To sustain weight loss in adulthood: Participate in at least 60-90 min of daily moderate-intensity physical activity while not exceeding caloric intake requirements.


The Power Behind Weight Loss?

Eating less has the biggest impact on weight loss.Exercise helps, but must exceed 60 minutes a day to be meaningful (more than most obese individuals are willing to endure) (Jeffery et al. Am J Clin Nutr 2003;78:684-689).

Exercise is more important in improving the health of the obese individual during weight loss than in accelerating weight loss.

Thus in the “battle of the bulge,” jab with exercise and deliver the knock-out blow with diet.


Box 13.10 So Then Why Exercise When Trying to Lose Weight?

Improves heart lung fitness (which tends to be low in obese individuals).

Improves overall health, and decreases the risk of obesity-related diseases such as heart disease, stroke, cancer, and hypertension.

Improves the blood lipid profile, with an increase in HDL-C and a decrease in triglycerides.

Improves psychological state, especially increased general well-being and vigor and decreased anxiety and depression.


The Surgeon General’s Call To Action To Prevent and Decrease Overweight and Obesity

The Nation must take action to assist Americans in balancing healthful eating with regular physical activity. Individuals and groups across all settings must work in concert to:

Ensure daily, quality physical education in all school grades. Reduce time spent watching television and in other similar sedentary behaviors. Build physical activity into regular routines and playtime for children and their families. Create more opportunities for physical activity at worksites. Make community facilities available and accessible for physical activity for all people. Promote healthier food choices, including at least 5 servings of fruits and vegetables each day, and reasonable portion sizes at home, in schools, at worksites, and in communities.


Exercise Prescription Guidelines

Initially, moderate levels of physical activity for 30 to 45 minutes, 3 to 5 days per week, should be encouraged.Starting a physical activity regimen may require supervision for some obese people. The need to avoid injury during physical activity is a high priority. Extremely obese persons may need to start with simple exercises that can be intensified gradually. For most obese patients, physical activity should be initiated slowly, and the intensity should be increased gradually.

Initial activities may be increasing small tasks of daily living. With time, the patient may engage in more strenuous activities.

A regimen of daily walking is an attractive form of physical activity for many people, particularly those who are overweight or obese.

The patient can start by walking 10 minutes, 3 days a week, and can build to 30 to 45 minutes of more intense walking at least 3 days a week and increase to most, if not all, days. All adults should set a long-term goal to accumulate at least 30 minutes or more of moderate-intensity physical activity on most, and preferably all, days of the week.Reducing sedentary time is another approach to increasing activity.


Box 13.11 Role of Physical Activity in Weight Management

Physical activity can influence body weight three different ways: Prevent weight gain in the first place.

Near-daily physical activity that is continued month after month, year after year, lowers the risk of weight gain with age.

Help one lose weight if overweight or obese.For most overweight and obese people, the extra weight lost with exercise is small when compared to that caused by the diet. Because most overweight people can only exercise moderately, the actual amount of energy expended tends to be lower than expected, and has a rather small impact on weight loss during a 2-4 month reducing diet.

• Maintain a good body weight after the excess weight is lost.Regular physical activity is one of the best predictors of those who are able to maintain weight loss over the long term.


Eating Disorders

An estimated 0.5 to 3.7% of females suffer from anorexia nervosa, and 1.1 to 4.2% in their lifetime.

85% of eating disorders have their onset during the adolescent age period.

Among the obese, 20-40% report problems with binge eating.

See Box 13.12 for danger signs and medical consequences of eating disorders.


Diagnostic Criteria for Anorexia NervosaDSM-IV, 1994, American Psychiatric Association

Refusal to maintain normal body weight (<85% of expected)

Intense fear of gaining weight or becoming fat, even though underweight

Body image disturbance

Amenorrhea (3 consecutive cycles)


Binge Eating Disorder

About 25%-50% of obese people suffer from binge eating, defined as consuming large amounts of food at one sitting while feeling out of control.

Binge eating disorder is diagnosed using these criteria:

During a binge eating episode, large amounts of food are eaten rapidly until feeling uncomfortably full, often while alone because of embarrassment.

The amount of food eaten is definitely larger than most people would eat in a similar period of time, and there is a feeling that one cannot stop eating or control what or how much one is eating.

The binge eater experiences feelings of disgust, depression, and extreme guilt after overeating.

The binge eating occurs, on average, at least two days a week for six months.

Binge eating is NOT associated with purging, fasting, or excessive exercise.


Diagnostic Criteria for Bulimia Nervosa DSM-IV, 1994, American Psychiatric Association

Recurrent episodes of binge eating (defined as eating a large amount of food within 2 h while feeling a lack of control)Recurrent inappropriate compensatory behavior to prevent weight gain (vomiting, laxatives, diuretics enemas, medications, fasting, excessive exercise)Binge eating and purging occur on average at least 2x/wk for 3 monthsBody image disturbance


Table 13.4Risk Factors for Anorexia Nervosa

High parental education and income

Early feeding problems

Low self-esteem

High neuroticism

Maternal over-protectiveness

Eating disorders among family members


Risk Factors for Bulimia NervosaChildhood obesity Early onset of menarche Weight concern Perfectionism Low self-esteem Social pressure about weight and eating Family dieting Eating disorders among family members Inadequate parenting Parental discord Parental psychopathology Childhood sexual abuse Chronic illness

nieman dc. exercise testing and prescription: a health-related approach. 6/e. copyright ©2007...

Documents

healthrelated approach

obesity obesity

mcgrawhill higher education

exercise testing

obesity slide

data nieman dc

health risks

parental obesity