Chapter 11 - Lecture notes 11 PDF

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Chapter 11: Weight Management LEARNING OBJECTIVES After completing this chapter, the student will be able to:  Discuss different methods for assessing body weight and body composition.  Explain the health risks associated with overweight and obesity.  Explain factors that may contribute to a weight problem, including genetic, physiological, lifestyle, and psychosocial factors.  Describe lifestyle factors that contribute to weight gain and loss, including the roles of diet, exercise, and emotions.  Identify and describe the symptoms of eating disorders and the health risks associated with them.  Design a personal plan for successfully managing body weight.

LECTURE OUTLINE This chapter presents information about appropriate methods of weight management, with particular emphasis on adopting permanent changes in lifestyle. The health implications of obesity and eating disorders also are discussed. I.

Basic Concepts of Weight Management A. The number of severely obese people has nearly tripled in the last decade. 1.

B.

C.

2. Some predict that by 2050, 75 percent of adults will be overweight and 42 percent will be obese. The most important element of body composition is the proportion of total weight that is fat—the percent body fat. 1. The body is composed of fat-free mass and body fat. a. Fat-free mass is composed of all the body’s nonfat tissues: bone, water, muscle, connective tissue, organ tissues, and teeth. b. There are two types of body fat. Subcutaneous fat makes up about 3 to 5 percent of total fat in men and 8 to 12 percent in women. Visceral fat exists primarily within adipose tissue, or fat cells, often located just below the skin and around major organs behind the abdominal wall. (1) Women tend to gain fat in the lower body more readily than men and are more likely to develop a pear-shaped body. (2) Men tend to deposit fat around their stomachs, thus developing an apple-shaped body. (3) Accumulation of fat around the waist has an adverse affect on health risk. (4) Total weight is not the most important issue for health; more important is the proportion of the body’s total weight that is made up of fat—the percent body fat. c. Most people who want to lose weight lose storage fat. Maintaining an energy balance is crucial to keeping a healthy ratio of fat to fat-free mass. Energy (calories) comes from food and is used for maintaining resting metabolism, for digestion, and 1. for fueling physical activity. Weight is maintained when energy taken in equals energy expende d. 2. 3.

D.

According to NIH, 68.8 percent of American adults are overweight, including more than 35.7 percent who are obese.

Changes in the consumption or expenditure of calories results in weight loss or gain. An individual has the most control over intake of calories through food and over expenditure of calories through exercise. The process of evaluating body weight and body composition varies with the assessment method used. Overweight is defined as total body weight above the recommended range for good health. Obesity is 1. defined as a more serious degree of overweight. 2. Height–weight charts list a range of body weight associated with the lowest mortality for people of particular sex, age, and height. This provides only an indirect measure of body fatness. Body mass index (BMI) correlates with percent body fat for average people and is useful for 3. classifying health risks of body weight if a person does not have access to more sophisticated methods. a. BMI does not distinguish between fat weight and fat-free weight . It can be inaccurate for short people (under 5 feet tall), muscular athletes, and older adults with little muscle mass due to inactivity or underlying disease.

b.

It also is not particularly useful for tracking changes in body composition—gains in muscle mass and losses of fat.

c. d. e.

BMI is defined as body weight (in kilograms) divided by the square of height (in meters). Standards set by NIH state that a BMI between 18.5 and 24.9 is considered healthy. A person with a BMI of 25 or above is classified as overweight, while someone with a BMI of 30 or above is considered obese. A BMI of 17.5 or less is sometimes used as a diagnostic criterion for the eating disorder anorexia nervosa.

f. 4.

The most accurate way to evaluate body composition is to determine percent body fat through one of several methods. Although many methods are available, there are no established specific guidelines for body composition assessment. a. Hydrostatic (underwater) weighing and BOD POD (a specialized body composition analysis device) allows the highly accurate calculation of percent body fat from body density. (1)

b.

c.

d.

E.

The Bod Pod uses air instead of water. A person sits in a chamber, and computerized pressure sensors determine the amount of air displaced by the person’s body. (2) With hydrostatic weighing people with more fat tend to float and weigh less underwater; leaner people tend to sink and weigh more underwater. Skinfold measurements determine the thickness of fat under the skin. Folds of skin are measured with a caliper, and the numbers are put into equations that calculate body fat percentage. Bioelectrical impedance analysis (BIA) measures the conduction of an electrical current through tissues. The current favors a path through fat-free tissues rather than fat ones. Fat percentages can be computed from these measurements. Scanning procedures are highly accurate but require expensive equipment; procedures include computed tomography, magnetic resonance imagery, dual-energy X-ray absorptiometry (DEXA), and dualphoton absorptiometry. (1) Other procedures include infrared reactance (Futrex 1100) and total body electrical conductivity (TOBEC).

Excess body fat and wellness 1. Obesity doubles mortality rates and can reduce life expectancy by 10 to 20 years. Obese people have a 50 to 100 percent increased risk of death from all causes compared with a. people with normal weight. b. If the current trends continue, scientists believe the average American’s life expectancy will soon decline by five years. c. Obesity is associated with unhealthy cholesterol and triglyceride levels, impaired heart function, and death from cardiovascular disease. d. Hypertension, many types of cancer, impaired immune function, gallbladder and kidney diseases, skin problems, impotency, sleep and breathing disorders, pregnancy complications, back pain, arthritis, and other bone and joint disorders also are health risks of obesity. e.

f.

2.

Obesity is also associated with complications of pregnancy, menstrual irregularities, urine leakage, psychological disorders, increased surgical risk, and psychological disorders and problems (such as depression, low self-esteem, and body dissatisfaction). There is a strong association between excess body fat and diabetes mellitus, a disease that causes a disruption of normal metabolism. Diabetes is the seventh leading cause of death in the United States. (1) Insulin, which stimulates cells to take up blood sugar (glucose) to produce energy, is normally secreted by the pancreas. This process is disrupted in a person with diabetes, and the level of glucose in the blood stream becomes excessive. (2) Diabetes is associated with kidney failure; nerve damage; circulation problems and amputation; retinal damage and blindness; and increased rates of heart attack, stroke, and hypertension. Excess body fat is a major risk factor for the most common form of diabetes (type 2 (3) diabetes).

The risks from obesity increase with its severity and are more likely to appear in people twice their desirable body weight.

a.

The risks depend on a person’s overall health and other risk factors, such as hypertension, unhealthy cholesterol levels, body fat distribution, and tobacco use.

b. c.

3.

A person with a BMI 25 or above should consult a physician to determine a healthy BMI. It is important to note that small weight losses—5 to 10 percent of total body weight—can lead to significant improvements in health. The distribution of body fat, that is, the location of fat on the body, is also an indicator of health. Men and postmenopausal women tend to store fat in the upper region of their body, a. particularly in the abdominal area (“apples”). The apple shape increases risk of high blood pressure, diabetes, early-onset heart disease, and certain types of cancer, strokes, and mortality. This risk is independent of a person’s BMI. b. Premenopausal women usually store fat in hips, buttocks, and thighs (“pears”). c. Risk from body fat distribution is usually assessed by measurement of waist circumference (the distance around the abdomen at the level of the hip bone, known as the iliac crest). A total waist measurement of more than 40 inches (102 cm) for men and 35 inches (88 cm) for women is associated with increased risk of disease. d. e.

II.

At any weight, people with a large waist circumference and/or additional risk factors are at risk for health problems.

Abdominal obesity and any two other risk factors associated with cardiovascular health put an individual at risk for metabolic syndrome. Waist circumference is a primary component of metabolic syndrome and a forewarning of diabetes and heart disease. 4. Body image consists of perceptions, images, thoughts, attitudes, and emotions. a. A negative body image is characterized by dissatisfaction with the body in general or some part of the body in particular. b. Many individuals who are not actually overweight are unhappy with their body weight or with some aspect of their appearance. c. Losing weight or getting cosmetic surgery does not necessarily improve body image. 5. Problems associated with very low levels of body fat—having body fat levels less than 8 to 12 percent for women and 3 to 5 percent for men—has been linked with reproductive, circulatory, and immune system disorders. a. Extremely lean people may experience muscle wasting and fatigue and are more likely to suffer from dangerous eating disorders. b. Women participating in sports in which weight and appearance are important may develop a condition known as the female athlete triad. (1) The triad consists of abnormal eating patterns and excessive exercising , followed by amenorrhea or the absence of menstruation, followed by premature osteoporosis. (2) If untreated, the triad can lead to reduced physical performance, increased incidence of bone fractures, disturbances of heart rhythm and metabolism, and even death. F. The “right” weight for any individual should be the result of a healthy lifestyle. A person’s weight may turn out to be somewhat higher than societal standards but will be the right weight for the individual. Factors Contributing to Excess Body Fat A. Genetic factors affect the development of obesity. Nutrigenomics is the study of how nutrients and genes interact and how genetic variations can cause people to respond differently to nutrients in food. More than 600 genes have been linked to obesity. 1. 2. Genes affect body size and shape, body fat distribution, metabolic rate, the ease with which weight is gained, and where on the body extra weight is first added. 3. If both parents are obese, their children have an 80 percent risk of being obese; children with one obese parent face a 50 percent risk of becoming obese. 4. Hereditary influences, however, must be balanced against the contribution of environmental factors such as diet and exercise. B. Physiological factors may contribute to obesity. Resting metabolic rate (RMR), the largest component of metabolism, is the energy required to maintain 1. vital body functions while the body is at rest. RMR accounts for about 65 to 70 percent of daily energy expenditure. The energy required to digest food accounts for an additional +/-10 percent, and the remaining 20 to 30 percent is expended during physical activity.

a. b. c.

d.

2.

3.

Heredity and behavior both affect metabolic rate. A higher RMR means that a person burns more calories while at rest and therefore can take in more calories without gaining weight. Weight loss or gain also affects metabolic rate. (1) When a person loses weight, both RMR and the energy required to perform physical tasks decrease. (2) The reverse occurs when weight is gained. (3) One of the reasons exercise is so important during a weight-loss program is that exercise, especially resistance training, helps maintain muscle mass and metabolic rate. Exercise increases RMR and increases muscle mass, which is associated with a higher metabolic rate. Exercise also burns calories, raising total energy expenditure and allowing a person to eat more without gaining weight.

Hormones play a role in the accumulation of body fat, especially in females during puberty, pregnancy, and menopause. a. The hormone leptin is secreted by the body’s fat cells and carried to the brain, where it appears to let the brain know the size of the body’s fat stores. The brain can regulate appetite and metabolic rate accordingly. b. Several hormones may be involved in regulating appetite. c. Research is using these hormones to develop treatments for obesity based on appetite control. The amount of fat (adipose tissue) the body can store is a function of the number and size of fat (adipose) cells. a.

When existing fat cells are filled, the body makes more, thereby increasing its ability to store fat.

b.

Some people are born with an above-average number of fat cells, which leads to the potential for storing more energy as body fat.

c. d.

C.

Overeating at critical times, such as childhood, can cause the body to create more fat cells. If a person loses weight and the fat cell content is depleted, it is unclear whether the number of fat cells also can be reduced. e. Not all fat cells are created equal. (1) Visceral adipose tissue, located at waist level, contains many biologically active substances such as inflammatory chemicals and growth factors, which can adhere to the lining of blood vessels, cause insulin resistance, and have a negative influence on cardiovascular health. (2) The more visceral fat you have, the greater your chances of developing insulin resistance, metabolic syndrome, type 2 diabetes, and heart disease. (3) In contrast, subcutaneous fat carries little or no health risk. Found more often in women than men, subcutaneous fat appears on the lower body–the hips, upper thighs, and buttocks. As a result of their body shape, people with excess subcutaneous fat are described as “pears.” Lifestyle factors, such as increased eating and reduced physical activity, also contribute to obesity. 1. Most overweight people eat an excess of high-fat, high-sugar, and high-calorie foods. 2.

Eating more frequently, eating larger portion sizes, and relying on fast food and packaged foods has contributed to obesity. a.

Many of those extra calories come from carbohydrates, such as refined sugar. Sugar-free soft drinks do not appear to help people lose weight.

3.

Children depend on their parents’ food choices in establishing eating habits. School lunch programs often include soda and snack machines, as well as on-site outlets for fast-food chains.

4.

While daily calorie intake has increased over the last two decades, physical activity levels have declined for most Americans. a. b.

Most schools have cut back on physical education classes and recess. Leisure time is filled with television viewing, surfing of the Internet, and playing of video games, rather than physical activities.

c.

On average, Americans exercise 15 minutes per day and watch 170 minutes of TV and movies.

D.

III.

Psychosocial factors may contribute to weight problems. 1. Eating may be used as a distraction from difficult emotions and to combat low moods, low energy levels, or low self-esteem. 2. Obesity is strongly linked with socioeconomic status; as income level goes up, the prevalence of obesity goes down. 3. In some cultures and families, food is a symbol of love and celebration. Eating patterns may be difficult to change if they are linked to family or cultural values. Adopting a Healthy Lifestyle for Successful Weight Management A. Four factors are crucial to a lifestyle that yields a healthy body weight: eating habits; level of physical activity; thinking and emotions; and coping strategies. B. Use MyPlate or DASH as the basis for a healthy diet. For weight management, pay special attention to total calories, portion sizes, energy density, fat and carbohydrate intake, and eating habits . MyPlate suggests approximate daily energy intakes based on gender, age, and activity level. 1.

To maintain current weight, calories consumed must equal calories expended. a. To lose weight, a person must reduce calorie intake and/or increase calories burned. b.

An increase in physical activity combined with moderate calorie restrictio n is the best approach for weight loss.

c.

2. 3.

For most people, maintaining weight loss is more difficult than losing the weight in the first place. Limiting portion sizes is crucial to maintaining good health. It is also easier than calorie counting. Pay attention to energy density—the number of calories per ounce or gram of weight of a food. a. Foods low in energy density are relatively heavy but have few calories. b.

C.

Fresh fruits, vegetables, and whole-grain foods are low in energy density; meat, ice cream, potato chips, and cookies are high in energy density. Fresh fruits contain fewer calories and more fiber than fruit juices or drinks. 4. Watch out for processed foods, which can be high in fat and sodium. Even processed foods labeled “fat-free” or “reduced fat” may be high in calories; such products may contain sugar and fat substitutes. Eating small, frequent meals on a regular schedule is healthier than skipping meals, which leads to 5. excessive hunger. Skipping meals can also lead to binge eating or snacking. a. For weight management, it is better to consume the majority of calories during the day rather than in the evening. b. A regular eating pattern and personal rules to govern food choices help structure decisions about diet. c. Declaring certain foods permanently off limits is usually less effective than striving for moderation. Regular physical activity is another important lifestyle factor in protecting against weight gain and is essential for maintaining weight loss. Physical activity burns calories and changes metabolism so that more food will be used for energy than stored as fat. 1. Cutting food intake to lose weight is difficult; increasing physical activity is a better approach. 2.

D.

Regular physical activity protects against weight gain and is essential for maintaining weight loss and improving quality of life.

Thinking and emotions play interrelated and crucial roles in the way we see ourselves as individuals, our approaches to life events, and our overall ability to maintain a healthy lifestyle. 1. Self-esteem and self-image are closely related to overall health. 2. People who are overweight may think poorly of themselves because they do not meet a preconceived notion of the “ideal self”; therefore, they consider themselves less than perfect or even failures. Such irrational beliefs can in turn lead to eating in response to stress and emotional disturbance. 3.

The beliefs and attitudes people develop and use give rise to self-talk, an interior dialogue about events that happen to and around them. Self-talk can be positive or negative. a. Positive self-talk encourages you throughout a task and praises you when it is complete. b.

Negative self-talk is deprecating and sel...