ch 13 PPT lecture(1)

Chapter 13 Lecture

The Science of NutritionThird Edition

© 2014 Pearson Education, Inc.

Achieving and Maintaining a Healthful Body Weight


What Is a Healthful Body Weight?

• Appropriate for age, physical development

• Maintained without constant dieting• Based on genetic background and family history of body shape and weight

• Compatible with normal blood pressure, lipid levels, and glucose tolerance

• Promotes good eating habits and allows for regular physical activity

• Acceptable to you



• Underweight: having too little body fat to maintain health

• Overweight: having a moderate amount of excess body fat



• Obese: having an excess of body fat that adversely affects health

• Morbid obesity: body weight exceeding 100% of normal, a very high risk for serious health consequences


Evaluating Body Weight

• Determining if a person's body weight is healthful should include:– Determining the body mass index (BMI)

– Measuring body composition– Assessing the pattern of fat distribution


Body Mass Index

• Expresses the ratio of a person's weight to the square of his or her height

• BMI = weight (kg)/height (m)2

• BMI = [weight (lbs)/height (inches)2] × 703

• BMI values below 18.5 or above 30 have increased health risks

• Not an indication of body composition


Body Composition

• Measure body fat and lean body mass by– Underwater weighing– Skinfold measurements– Bioelectric impedance analysis– Near-infrared reactance– Dual-energy x-ray absorptiometry (DXA)

– Bod Pod™


Fat Distribution Pattern

• Apple-shaped fat patterning—upper body– Increased risk for chronic diseases– Men tend to store fat in the abdominal region

• Pear-shaped fat patterning—lower body– No significant increased chronic disease risk

– Women tend to store fat in the lower body


Fat Distribution Pattern

• Abdominal fat increases risk for chronic disease

• Waist-to-hip ratio– Men: waist-to-hip ratio higher than 0.90

– Women: waist-to-hip ratio higher than 0.80

• Waist circumference– Men: above 40 in. (or 102 cm)– Women: above 35 in. (or 88 cm)


Gaining and Losing Weight

• Weight gain or loss depends on– Energy intake vs. energy expenditure

– Genetic factors– Childhood weight– Behavioral factors– Social factors


Energy Balance

• Energy balance equation– Energy intake = energy expenditure– Energy intake is kcal from food, beverages

– Energy expenditure is energy expended at rest and during physical activity


Energy Intake

• Calculating the energy that is in a particular food – Carbohydrate is 4 kcal/g – Protein is 4 kcal/g– Fat is 9 kcal/g– Alcohol is 7 kcal/g

• 1 cup of quick oatmeal has 142 kcal– 6 grams protein × 4 kcal/gram = 24 kcal– 25 grams carbohydrate × 4 kcal/gm = 100 kcal – 2 grams fat × 9 kcal/gram = 18 kcal– Total kcal = 24 kcal + 100 kcal + 18 kcal = 142 kcal


Energy Intake

• When total daily energy intake exceeds the amount of energy expended, weight gain results

• An excess intake of approximately 3,500 kcal will result in a gain of 1 pound– Without exercise, this gain will likely be fat


Energy Expenditure

• Energy is expended to maintain basic body functions and to perform activities

• Total 24-hour energy expenditure is composed of three components: – Basal metabolic rate (BMR)– Thermic effect of food (TEF)– Energy cost of physical activity


Energy Expenditure

• Direct calorimetry is a method that measures the amount of heat the body releases

• Indirect calorimetry estimates energy expenditure by measuring oxygen consumption and carbon dioxide production


Basal Metabolic Rate (BMR)

• Energy expended to maintain basal (resting) functions of the body

• Includes respiration, circulation, maintaining body temperature, new cell synthesis, secretion of hormones, and nervous system activity

• Primary determinant of BMR is the amount of lean body mass


Energy Expenditure

• Thermic effect of food (TEF)– Energy expended to process food– About 5−10% of the energy content of a meal

• Energy cost of physical activity – About 15−35% of total daily energy output


Genetic Factors

• Influence height, weight, body shape, metabolic rate

• About 25% of one's body fat is accounted for by genetic influences

• Different ideas have been suggested to explain the impact of genetics on body fat– Thrifty gene theory– Set-point theory


Thrifty Gene Theory

• Proposes that a gene (or genes) causes people to be energetically thrifty

• People with this gene expend less energy than other people

• Protects from starvation during times of extreme food shortages

• A ''thrifty gene'' has not been identified


Set-Point Theory

• Suggests that body weight stays within a narrow range (set point)

• Compensates for changes in energy balance and keeps a person's weight at his or her set point


Composition of the Diet

• Theory states that overeating dietary fat promotes storage as adipose tissue

• Overeating carbohydrate or protein: – Used for energy, storage, or tissue building

– Smaller amount of the excess stored as fat

– Also leads to weight gain• Important to maintain a balanced diet combining fat, carbohydrate, and protein

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Physiologic Factors

• Hunger and satiety• Proteins affect the regulation of appetite and storage of body fat – Leptin acts to reduce food intake – Ghrelin stimulates appetite – Peptide YY (PYY) decreases appetite – Uncoupling proteins in brown adipose tissue increase energy expenditure


Physiologic Factors

• Increase satiety (or decrease food intake) – Hormones—serotonin, cholecystokinin (CCK)

– Increase in blood glucose levels after meal

– Stomach expansion– Nutrient absorption from the small intestine

• Decrease satiety (or increase food intake) – Hormones—beta-endorphins – Neuropeptide Y – Decreased blood glucose levels


Cultural and Economic Factors

• Religious beliefs • Learned food preferences • Fast-food culture• Sedentary lifestyle• Economic status • Access to healthcare


Psychologic and Social Factors

• Appetite: psychological drive to eat• Meal timing and size: portion distortion

• Sight and fragrance of foods • Mood, depression• Barriers to physical activity • Technological lifestyle • Social pressures


Achieve and Maintain Healthful Weight• Healthful weight change requires

– Gradual change in energy intake– Regular and appropriate physical activity

– Behavior modification techniques• Tips

– Avoid fad diets– Achieve negative energy balance

ABC News Video: Fad Diets

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Weight-Loss Diets

• Moderate-fat, high-carbohydrate, moderate-protein diets – Balanced in nutrients: 20−30% calories from fat, 55−60% from carbohydrate, 15−20% from protein

– Weight Watchers, Jenny Craig, DASH diet, and the USDA MyPyramid

– Gradual weight loss (1−2 pounds per week)

– Typical energy deficits = 500−1,000 kcal per day


Weight-Loss Diets

• High-fat, low-carbohydrate, high-protein diets – 55–65% of total energy intake as fat and less than 100 g of carbohydrate per day

– Dr. Atkins' Diet Revolution, Protein Power

– Cause ketosis, which will decrease blood glucose and insulin levels and reduce appetite

– Concerns about long-term compliance, potential health risks, and side effects


Weight-Loss Diets

• Low-fat and very-low-fat diets – About 11−19% of total energy as fat, while very-low-fat-diets contain less than 10%

– Dr. Dean Ornish's Program for Reversing Heart Disease and The New Pritikin Program

– Emphasize complex carbohydrates and fiber – Regular physical activity is a key component

– Lower LDL cholesterol, triglyceride, glucose, and insulin levels, and lower blood pressure


Achieve and Maintain Healthful Weight• Set realistic and achievable goals that are:– Specific– Reasonable– Measurable

ABC News Video: Crash Diet

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ABC News Video: Diet Meals

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Achieve and Maintain Healthful Weight• Follow recommended serving sizes• Reduce high-fat and high-energy food intake

• Consume foods that are relatively low in energy density

• Participate in regular physical activity

• Incorporate appropriate behavior modifications into daily lifeABC News Video: Extreme Healthy

Eating: What is Orthorexia?PLAY

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Underweight

• As harmful as obesity• Can be due to many factors

– genetics– consuming too few Calories for exercise level

– heavy smoking– underlying disease– Anorexia nervosa


Safe and Effective Weight Gain

• Underweight: BMI of less than 18.5 kg/m2

• Limit fat: <30% of total energy intake

• Eat 500 to 1,000 extra kcal/day• Eat frequently throughout the day• Avoid tobacco (depresses appetite and increases BMR)

• Exercise regularly with resistance training


Dietary Supplements

• Dangerous or ineffective supplements can be marketed and sold without meeting the FDA's strict safety and quality standards

• Insufficient evidence to support their use

• Stimulants speed up metabolic processes; are controversial; and may be dangerous– Caffeine, phenylpropanolamine (PPA), and ephedra


Protein Supplements

• Include amino acid supplements, anabolic steroids, and androstenedione

• Do not enhance muscle gain or result in improvements in strength

• Cause major health problems: unhealthful changes in blood cholesterol, mood disturbances


Overweight

• BMI between 25 and 29.9 kg/m2

• Health risks: high blood pressure, heart disease, type 2 diabetes, sleep disorders

• Many overweight people will become obese

• Recommend healthful eating and regular physical activity to prevent additional weight gain, achieve a healthful weight, support long-term health


Obesity and Morbid Obesity

• Obesity: BMI from 30 to 39.9 kg/m2

• Morbid obesity: >100% normal weight• Considered an epidemic in the United States

• Linked to many chronic diseases: – Hypertension– Dyslipidemia– Diabetes– Heart disease– Stroke


Metabolic Syndrome

• A cluster of factors increases risk for heart disease, type 2 diabetes, and stroke:– Abdominal obesity (waist circumference ≥40 inches for men, 35 inches for women)

– Triglyceride levels (≥150 mg/dL)– HDL cholesterol levels (<40 mg/dL in men and 50 mg/dL in women)

– Blood pressure (≥130/85 mm Hg)– Fasting blood glucose ≥100 mg/dL


Obesity: Weight Loss Medications

• Used only with a physician's supervision

• Long-term safety and efficacy explored• Sibutramine (Meridia): reduces appetite

• Orlistat (Xenical): inhibits fat absorption

• Should only be used if a person has– A BMI of 30 kg/m2

– A BMI of 27 kg/m2 and other health risk factorsABC News Video: Obesity in

AmericaPLAY

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ABC News Video: Can You Be Slim and Obese

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ABC News Video: Diet Dream Drug – Hope or Hype: Pros and Cons of Alli

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How do People Become Obese?

• Genetic and physiologic factors• Childhood obesity linked to adult obesity

• Critical periods might increase risk– Gestation and early infancy– Period of weight gain (adiposity

rebound) that occurs between 5 and 7 years of age

– Adolescence (or puberty)• Social factors


Obesity Treatment

• Lifestyle: low-Calorie diet, regular exercise

• Prescription medications• Over-the-counter medications/supplements

• Surgery for morbid obesity– Vertical banded gastroplasty– Gastric bypass surgery– Gastric banding– Liposuction

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