CHAPTER

9Achieving and Maintaining a Healthful Body Weight

Chapter 9 Outline

I. Is Your Body Weight Healthful?

A. Understand what a healthful body weight really is.

1. A weight appropriate for one’s age and physical development.

2. A weight based on genetic background and family history of body shape and weight.

3. A weight achieved and sustained without restraining food intake or constantly dieting.

4. A weight that is compatible with normal blood pressure, lipid levels, and glucose tolerance.

5. A weight that promotes good eating habits and allows for participation in regular physical activity.

6. A weight that is acceptable to the individual.

B. Determine your body mass index (BMI).

1. Underweight is defined as having too little body fat to maintain health.

2. Normal weight is defined as having an adequate but not excessive level of body fat for health.

3. Overweight is defined as having a moderate amount of excess body fat.

4. Obesity is defined as having an excess of body fat that adversely affects health.

5. Morbid obesity is defined as a body weight that exceeds 100 percent of normal.

6. Why is BMI important?

a. BMI less than 18.5 is associated with increased risk of health problems and death.

b. BMI greater than 30 is associated with increased risk for many chronic diseases.

c. BMI greater than 40 is associated with very high risk for serious health consequences.

7. There are limitations to the BMI.

a. BMI is of limited value for people with a disproportionately high muscle mass.

C. Measure your body composition.

1. Underwater weighing is one of the most accurate methods for assessing body composition.

2. Skinfold measurements involve pinching and measuring a person’s fold of skin and fat.

3. Bioelectrical impedance analysis (BIA) involves sending a low-level electric current through a person’s body.

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4. Dual-energy x-ray absorptiometry (DEXA) uses very-low-level x-rays to differentiate among bone tissue, lean tissue, and fat.

5. The Bod Pod uses air displacement to measure body composition.

D. Assess your fat distribution pattern.

1. The waist-to-hip ratio and waist circumference can determine the type of fat patterning.

II. What Makes Us Gain and Lose Weight?

A. We gain or lose weight when our energy intake and expenditure are out of balance.

1. Energy intake is the food and beverages we consume each day.

2. Energy expenditure includes more than just physical activity.

a. Basal metabolic rate (BMR) is energy output at rest.

b. The thermic effect of food is the energy expended to process food.

c. The energy cost of physical activity is highly variable.

B. How many kilocalories do you need?

1. Calculation of BMR and estimated daily activity level can be used to estimate energy needs.

C. Limitations of the Energy Balance Equation

1. The energy balance equation relates food intake to energy expenditure.

2. Current research points out that the equation fails to account for many factors that can alter energy intake and expenditure or to help explain why people gain and lose weight differently.

D. Genetic factors affect body weight.1. The FTO gene is currently under research as it appears to stimulate excessive food in-

take and may diminish feelings of satiety.

2. The thrifty gene theory suggests that some people possess a gene(s) that causes them to be energetically thrifty.

3. The set-point theory suggests that our bodies are designed to maintain weight within a narrow range or “set point.”

E. Composition of the diet affects fat storage.

F. Metabolic factors influence weight loss and gain.

1. A relatively low metabolic weight equals a risk for weight gain.

2. A low level of spontaneous physical activity, or fidgeting, indicates a risk for weight gain.

3. A low amount of sympathetic nervous system activity points to a risk for weight gain.

4. A lowered ability to metabolize fat indicates a risk for weight gain.

G. Physiologic factors influence body weight.

1. Ghrelin plays a role in appetite regulation through actions on the hypothalamus.

2. Peptide YY decreases appetite and inhibits food intake.

3. Uncoupling proteins in the mitochondria affect energy expenditure. This is especially prevalent in brown adipose tissue.

H. Cultural and economic factors affect food choices and body weight.

I. Social factors influence behavior and body weight.

1. Some social factors promote overeating.

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2. Some social factors promote inactivity.

3. Social pressures can promote underweight.

III. How Can You Achieve and Maintain a Healthful Body Weight?

A. If you decide to follow a popular weight-loss plan, choose one based on the three strate-gies.

1. Avoid fad diets.

2. Diets based on macronutrient composition may or may not work for you.

a. Diets high in carbohydrate and moderate in fat and protein have been well-re-searched and evidence indicates that they are effective in decreasing body weight.

b. Diets low in carbohydrate and high in fat and protein focus mainly on reducing carbohydrate intake.

c. Low-fat and very-low-fat diets are restrictive but seem to result in weight loss and decreased blood pressure, as well as other positive metabolic changes.

B. If you decide to design your own weight-loss plan, include the three strategies.

1. Set realistic goals.

2. Eat smaller portions of lower-Calorie foods.

3. Participate in regular physical activity.

4. Incorporate appropriate behavior modifications into daily life.

IV. How Can You Avoid Obesity?

A. Why is obesity harmful?

1. Obesity is linked to many chronic diseases and complications.

2. Abdominal obesity is one of five risk factors collectively referred to as metabolic syndrome.

B. Why do people become obese?

1. Obesity is a multifactorial disease.

a. Genetic and physiologic factors influence obesity risk.

b. Childhood obesity is linked to adult obesity.

c. Social factors appear to influence obesity risk.

C. Does obesity respond to treatment?

1. Twenty percent of obese people succeed in long-term weight loss.

2. Lifestyle changes can help.

3. Weight loss can be enhanced with prescribed medications.

4. Surgery can be used to treat morbid obesity.

V. What If You Are Underweight?

A. Consume more energy than is expended.

B. Eat frequent, healthy meals.

C. Incorporate resistance training into a regular exercise routine.

VI. Disordered Eating: Are You At Risk?

A. Disordered eating is a general term used to describe a variety of abnormal or atypical eating behaviors used to achieve or maintain a lower body weight.

B. An eating disorder is a psychiatric condition that must be diagnosed by a physician.

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1. Anorexia nervosa is a potentially life-threatening eating disorder that is characterized by self-starvation.

2. Bulimia nervosa is characterized by recurrent episodes of extreme overeating and compensatory behaviors to prevent weight gain.

C. Eating behaviors occur on a continuum.

D. Many factors contribute to disordered eating behaviors, including:

1. Influence of genetics.

2. Influence of social factors.

3. Influence of psychological factors.

E. Anorexia nervosa is a potentially deadly eating disorder.

1. Refusal to maintain body weight at or above a minimally normal weight for age and height.

2. Intense fear of gaining weight or becoming fat, even though considered underweight by all medical criteria.

3. Amenorrhea in females who are past puberty.

F. Bulimia Nervosa is characterized by bingeing and purging.

1. Recurrent episodes of binge eating followed by purging.

2. Body shape and weight unduly influencing self-evaluation.

G. Binge-eating disorder can cause significant weight gain.

1. Health risks of binge-eating disorder include obesity and the risks associated with obesity.

H. Disordered eating can be part of a syndrome

1. Night-eating syndrome is linked to insomnia and depression.

2. Sports that emphasize leanness increase the risk for the female athlete triad.

3. Three disorders characterize the female athlete triad.

a. Disordered eating is the first component of the female athlete triad.

b. Menstrual dysfunction can result from energy restriction combined with high levels of physical activity.

c. Osteoporosis may result from reduced estrogen levels.

I. Treatment of disordered eating requires a multidisciplinary approach.

1. nutritional management

2. psychological treatment

3. medications

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