21

Obesity, Diabetes, and Physical Activity

chapter

Learning Objectives

• Differentiate between overweight and obesity• Find out how body mass index is calculated and how

BMI is used to differentiate between normal weight, overweight, and obesity

• Discover the prevalence of obesity in the United States and the health-related problems that are associated with obesity

• Learn how body weight is precisely controlled under most conditions (set point) and how it can get out of balance, resulting in weight gain or loss

(continued)

Learning Objectives (continued)

• Understand the three components of energy expenditure and how they function in the control of body weight

• Determine the etiology of obesity, understanding that genetics plays a role but other factors interact with genetics

• Examine the interrelationship of obesity, coronary artery disease, hypertension, and diabetes

• Learn the most effective methods for treating and preventing obesity

• Review the two types of diabetes and the role exercise plays in their treatment

Terminology

Overweight is body weight that exceeds the normal or standard weight for a particular person based on height and frame size

Obesity is the condition of having an excessive amount of body fat (in general, more than 25% in men and more than 35% in women)

Body mass index (BMI) is the most widely accepted standard to estimate obesity

BMI = body weight (kg) / height (m2)

Waist circumference reflects visceral abdominal fat, which increases the risk for disease

Obesity and Overweight in the U.S.

• Prevalence has dramatically increased since the 1970s• 31% of men and 33% of women in the United States

are obese• 71% of men and 62% of women in the United States

are overweight or obese• Prevalence in children has increased markedly since

1980• The average adult gains 0.45-0.90 kg (1-2 lb) per year

after age 25

The Increasing Prevalence of Overweight in the United States From 1960-2004

Data from Flegal et al., 1998; Flegal et al., 2002; and Ogden et al., 2006.

The Increasing Prevalence of Obesity in the United States From 1960-2004

Data from Flegal et al., 1998; Flegal et al., 2002; and Ogden et al., 2006.

The Increasing Prevalence of the Combination of Overweight and Obesity

in the United States From 1960-2004

Data from Flegal et al., 1998; Flegal et al., 2002; and Ogden et al., 2006.

Prevalence of Overweight, Obesity, and the Combination of Both in (a) Men and (b)

Women by Race (2004)

Data from C.L. Ogden et al., 2002, "Prevalence of overweight and obesity in the United States, 1999-2004," Journal of the American Medical Association 295: 1549-1555.

Data from C.L. Ogden et al., 2002, “Prevalence of overweight and obesity in the United States, 1999-2004,” Journal of the American Medical Association 295: 1549-1555.

Increasing Prevalence of Overweight in Children and Adolescents in the United

States From 1963 Through 2004

Data from C.L. Ogden et al., 2002, "Prevalence and trends in overweight among US children and adolescents," Journal of the American Medical Association 288: 1728-1732; and from C.L. Ogden et al., 2006, "Prevalence of overweight and obesity in the United States, 1999-2004," Journal of the American Medical Association 295: 1549-1555.

Control of Body Weight

Body weight appears to be regulated around a set point

Resting Metabolic Rate (RMR)– 60% to 75% of daily energy expended

Thermic Effect of a Meal (TEM)– Energy expended for digestion, transport, and

metabolism of ingested food– 10% of daily energy expended

Thermic Effect of Activity (TEA)– Energy above RMR needed to perform activities– 15% to 30% of daily energy expended

The Three Componentsof Energy Expenditure

Adapted, by permission, from E.T. Poehlman, 1989, "A review: Exercise and its influence on resting energy metabolism in man," Medicine and Science in Sports and Exercise 21: 515-525.

Etiology of Obesity

• Genetic factors• Decreased physical activity• Overconsumption of calories• Hormonal imbalances• Emotional trauma• Homeostatic imbalances• Cultural influences

Similarity in Weight Gains Between Twins in Response to a 1,000 kcal

Increase in Dietary Intake for 84 Days of a 100-Day Study

Adapted, by permission, from C. Bouchard et al., 1990, “The response to long-term overfeeding in identical twins,” New England Journal of Medicine 322: 1477-1482. Copyright © 1990 Massachusetts Medical Society. All rights reserved.

A Genetic Predisposition to Obesity: The Pima Indians

The BMI for Pima Indian men and women living in Arizona and in northern Mexico (2006)

From L.O. Schultz et al., 2006, “Effects of traditional and western environments on prevalence of type 2 diabetes in Pima Indians in Mexico and the U.S.,” Diabetes Care 29: 1866-1871.

Health Risks Associated With Excessive Weight and Obesity

Increased mortality rates of the following diseases:• Heart disease• Hypertension• Type 2 diabetes• Certain types of cancer• Gall bladder disease• Osteoarthritis

The Relationship of Body Mass Index to Excess Mortality

Bray, G.A. “Obesity: Definition, diagnosis and disadvantages.” MJA 1985; 142: S2-S8. © Copyright 1985. The Medical Journal of Australia—reproduced with permission.

Obesity-Induced Changes in Normal Body Function

• Respiratory problems including sleep apnea• Polycythemia (increased red blood cell production)• Thrombosis (blood clot)• Hypertrophic cardiomyopathy (enlarged heart)• Congestive heart failure• Decreased exercise tolerance

Fat Distribution

Upper Body (Android) Obesity• Fat is stored in upper body and abdominal area

(apple-shaped)• Occurs more frequently in men• Carries greater risk for CAD, hypertension, stroke,

elevated blood lipids, and diabetes

Lower Body (Gynoid) Obesity• Fat is stored in the lower body around the hips,

buttocks, and thighs (pear-shaped)• Occurs more frequently in women

(a) Upper Body Obesity,(b) Lower Body Obesity

CT Scans to Assess Visceral Fat: (a) Undergoing a CT Scan, (b) Scan of a Lean Subject, (c) Scan

of a Subject With More Visceral Fat

a

b c

Scans from J.C. Seidell et al., 1987, “Obesity and fat distribution in relation to health – Current insights and recommendations,” World Review of Nutrition and Dietetics 50: 57-91.

Diseases That BenefitFrom Weight Reduction

• Angina pectoris• Hypertension• Congestive heart failure• Myocardial infarction• Varicose veins• Diabetes• Orthopedic problems

General Treatment of Obesity

• Not everyone responds to the same intervention in the same way

• Weight loss should not exceed 0.45-0.9 kg (1-2 lb) per week

• Weight loss should be considered a long-term project• Extreme weight loss measures

– Very low calorie diets (350-400 kcal per day)– Weight-loss drugs– Surgery (intestinal by-pass, gastric banding)

Obesity

Key Points• The etiology of obesity is not simple• There is a genetic component to obesity• Overweight and obesity are associated with

increased risk of general excess mortality• Respiratory problems are common among people

with obesity• Obesity increases the risk of certain chronic

degenerative diseases• Upper body obesity increases the risk of developing

CAD, hypertension, stroke, elevated blood lipids, diabetes, and metabolic syndrome

(continued)

Obesity (continued)Key Points• Emotional or psychological problems may contribute to

obesity• Individuals will vary in their response to obesity

treatment• Weight loss should generally not exceed 0.9 kg (2 lb)

per week and should be considered a long-term project• Diet modifications, including reducing fat and simple

sugar intake, are sufficient to help most people lose weight

• The use of drugs or surgery in the treatment of obesity is generally not recommended unless deemed necessary for the patient’s health by a physician

Role of Physical Activityin Weight Control

• Altered body composition– ↓ Total weight– ↓ Fat mass and relative body fat – Either maintain or ↑ FFM

• Increases metabolism after exercise (EPOC)• Decreases visceral fat stores

Mechanisms for Changein Body Weight

Energy intake – energy excreted = RMR + TEM + TEA

• Increased energy expenditure from:– Energy expended during exercise– Increase in metabolic rate after exercise (EPOC)

• Exercise can suppress appetite• Resting metabolic rate may increase slightly

Low-Intensity Aerobics

• Low-intensity aerobic activity does not necessarily lead to a greater expenditure of calories from fat

• Total caloric expenditure for a given period of time is much less compared with higher-intensity aerobic activity

Rate of Fat Oxidationat Various Exercise Intensities

Reprinted, by permission, from J. Acten, M. Gleeson, and A.E. Jeukendrup, 2002, “Determination of the exercise intensity that elicits maximal fat oxidation,” Medicine and Science in Sports and Exercise 34: 92-97.

Diabetes Mellitus

• Characterized by high blood glucose concentrations• Type 1: inability of the -cells in the pancreas to

produce insulin– 5-10% of all diabetes cases

• Type 2: ineffectiveness of insulin to facilitate the transport of glucose into the cells (insulin resistance)– 90-95% of all diabetes cases

• Gestational: diabetes that develops during pregnancy– 4% of all pregnancies

• Prediabetes: impaired fasting glucose and/or impaired glucose tolerance

Symptoms of Diabetes

• Frequent urination• Excessive thirst• Unexplained weight loss• Extreme hunger• Sudden vision changes• Tingling or numbness in hands or feet• Feeling very tired much of the time• Irritability• Sores that are slow to heal• More infections than normal

Prevalence of Diabetes

• ~14.6 million Americans have been diagnosed• ~6.2 million people are undiagnosed• ~41 million people are prediabetic• The risk of developing diabetes is higher in Mexican

Americans and American Indians• Type II diabetes in children has increased 10-fold over

the last 20 years (estimate)

Etiology of Diabetes

• Type 1: Destruction of insulin-secreting -cells (heredity)

• Type 2: Delayed insulin secretion or impaired insulin reaction, insulin resistance, excessive glucose output from the liver

• Type 2: -cells become less responsive to increased blood glucose, target cells have a reduction in the number and/or activation of the insulin receptors

Health Problems and Diabetes

• Coronary artery and peripheral vascular disease• Cerebrovascular disease and stroke• Hypertension• Peripheral vascular disease• Kidney disease• Eye disorders, including blindness• Toxemia during pregnancy

Treating Diabetes

• Individualized insulin administration and monitoring(if needed)

• Well-balanced diet• Regular exercise and physical training• Drugs: sulfonylureas, biguanides• Weight loss

Physical Activityand Type 1 Diabetes

• In people with type 1 diabetes, exercise may or may not improve their glycemic control but will help lower their risk for coronary artery disease

• Blood glucose concentration must be carefully monitored during exercise in people with type 1 diabetes so that they can alter their insulin dosage

• Attention to foot care is especially important for individuals with type 1 diabetes due to decreased sensation and peripheral blood flow in the feet

Physical Activityand Type 2 Diabetes

• Type 2 diabetes responds well to exercise• Membrane permeability to glucose improves with

exercise, likely associated with an increase in GLUT-4 receptors, which decreases the person’s insulin resistance and increases insulin sensitivity