Energy Balance, Weight Control, and Eating Disorders

Transcription

1 Energy Balance, Weight Control, and Eating Disorders

2 What is the Energy Balance? It is the relationship between energy intake and energy expenditure. Energy Equilibrium: the calories consumed from food and beverage (energy intake) match the amount of energy expended.

3 Positive Energy Balance Energy intake exceeds energy expended. The excess energy consumed is stored, resulting in weight gain. Positive energy balance is desired in some situations, such as during the growth stages of the life cycle and to restore body weight to healthy levels after losses caused by starvation, disease, or injury.

4 Negative Energy Balance Energy intake is less than energy expenditure. Weight loss occurs because energy stored in the body fat and muscle is used to make up for the shortfall in energy intake. Negative energy balance is desired in adults when body fatness exceeds healthy levels. Negative energy balance during growth stages of the life cycle generally is not recommended because it can impair normal growth.

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6 Energy Intake The amount of energy in a food or beverage can be estimated using nutrient databases or nutrient analysis software. Calorie value in these tables and programs can be derived by directly measuring calorie content using device called bomb calorimeter

7 Energy Intake Bomb Calorimeter Bomb calorimeters measure calorie content by igniting and burning a dried portion of food. The burning food raises the temperature of the water surrounding the chamber holding the food. The increase in water temperature indicates the number of kilocalories in the food because 1 kilocalorie equals the amount of heat needed to raise the temperature of 1kg of water by 1 c.

8 Energy Expenditure The body uses energy for 4 general purposes: Basal metabolism physical activity Thermic effect of food (TEF) Thermogenesis

9 Major components of energy intake and expenditure The size of each component shows the relative contribution of that component to energy balance. Alcohol is an additional source of energy only for those who consume it.

10 1- Basal Metabolism Expressed as basal metabolic rate (BMR) Represents the minimum amount of energy expended in a fasting state(12hours or more) to keep a resting, awake body alive in a warm, quiet environment.

11 Basal Metabolic Rate (BMR) For sedentary person, basal metabolism accounts for about 60 to 70% of total energy expenditure. The processes involved include the beating of the heart, respiration by the lungs, and the activity of other organs, such as the liver, brain, and kidney. The term resting metabolism is used (expressed as resting metabolic rate [RMR]) RMR is 6% higher than BMR is primarily affected by lean body mass, body surface area, and thyroid hormone concentrations.

12 BMR and RMR A rough estimate of basal metabolic rate for women is 0.9kcal/kg per hour and 1.0 kcal/kg for men. Calculate the BMR for a (70 kg) women

13 2- Physical Activity Physical activity is energy use above the amount expended when at rest. Climbing stairs rather than riding the elevator, walking rather than driving to the store, and standing in a bus rather than sitting increase physical activity and, hence, energy expenditure.

14 Classwork leads to mental activity, but little physical activity. Hence, energy is burned at a rate of only about 1.5 kcal per minute.

15 3- Thermic Effect of Food(TEF) The thermic effect of food is the energy the body uses to digest, absorb, transport, store, and metabolize the nutrients consumed in the diet. The TEF accounts for about 5 to 10% of the energy consumed each day. Calculate the TEF if daily energy intake were 3000 kcal.

16 In a sedentary person, about 70 to 80% of energy use is accounted for by basal metabolism and thermic effect of food.

17 3- Thermic Effect of Food(TEF) Food composition influences TEF. The TEF value for a protein-rich meal(20 to 30% of the energy consumed) is higher than that of a carbohydrate-rich(5 to 10%) or fatrich(0 to 3%) meal because it takes more energy to metabolize amino acids into fat than to convert glucose into glycogen or transfer absorbed fat into adipose stores.

18 4- Adaptive Thermogenesis Thermogenesis is heat production caused by shivering when cold, fidgeting, and other stimuli. It goes by other names, such as thermoregulation and non-exercise activity thermogenesis(neat).

19 Measuring Energy Expenditure 1. Direct calorimetry 2. Indirect calorimetry 3. Estimated energy requirements(eers)

20 1. Direct Calorimetry Estimates energy expenditure by measuring the amount of body heat released by a person.

21 2. Indirect Calorimetry The most commonly used method to determine energy use by the body, involves collecting expired air from an individual during a specified amount of time. This method works because a predictable relationship exists between the body s use of energy and the amount of oxygen consumed and carbon dioxide produced.

22 Indirect calorimetry measures oxygen intake and carbon dioxide output to determine energy expended during daily activities.

23 3. Estimated Energy Requirements(EERs) Are based on formulas developed by the Food and Nutrition Board that can be used to estimate energy needs using a person s weight, height, gender, age, and physical activity level. Men 19 years and older EER= 662-(9.53x AGE) +PA x(15.91x WT x HT) Women 19 years and older EER= 354-(6.91x AGE) +PA x(9.36x WT+726 x HT)

24 Energy expenditure estimates from my pyramid

25 Eating Behavior Regulation Groups of cells in the hypothalamus and other regions in the brain affect hunger, the primarily internal desire to find and eat food. These cells monitor macronutrients and other substances in the blood and read low amounts as a signal to promote feeding.

26 Eating Behavior Regulation A variety of external (appetite related) forces, such as food availability, affect satiety. Hunger cues combine with appetite cues to promote feeding. Numerous factors elicit satiety, such as flavor, smell, chewing, and the effects of digestion, absorption, and metabolism.

27 Although some factors have an impact on both hunger and appetite, internal factors are mainly responsible for hunger, whereas external factors primarily influence appetite. These factors combine to play a role in the complex and interrelated processes that help determine when, what, and how much we eat.

28 Factors affecting satiety

29 Estimating Body Weight and Composition A person of healthy weight generally shows good health and performs daily activities without weight-related problems. 1- Body Mass Index(BMI) 2- Measuring Body Fat Content 3- Assessing Body Fat Distribution

30 1- BMI BMI (weight in kilograms/height in meters height in meter)of 18.5 to 25 is one measure of healthy weight, although weight in excess of this value may not lead to ill health. A healthy weight is best determined in conjunction with a thorough health evaluation by a health-care provider. A body mass index of 25 to 29.9 represents overweight Obesity is defined as a total body fat percentage over 25%(men) or 35%(women), or a body mass index of 30 or more.

31 Height-weight table based on BMI

32 Examples of body shapes associated with different BMI values

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34 2- Measuring Body Fat Content Body fat can range from 2 to 70% of body weight. Desirable amounts of body fat are about 8 to 24% of body weight for men and 21 to 35% for women. Men with over 24% body fat and women with over about 35% body fat are considered obese.

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36 2- Measuring Body Fat Content To measure body fat content accurately using typical methods, both body weight and body volume must be measured. To estimate body volume, underwater weighing is one of the most accurate(2 to 3% error margin). This technique determines body volume by measuring body weight when under water and body weight in air and entering these values into a mathematical formula that accounts for the differences in the relative densities of fat tissue and lean tissue.

37 During underwater weighing, the person exhales as much air as possible and then holds his or her breath and bends over at the waist. When the person is totally submerged, under water weight is recorded. Body volume is calculated by entering this value and weight in air into formula.

38 Air Displacement Another method for determining body volume, measures the space a person takes up inside a small chamber. This method is accurate alternative to underwater weighing. Once body weight and body volume are known, body density and body fat can be calculated:

39 Abodypod* determines body volume by measuring the volume of air displaced when a person sits in a sealed chamber for a few minutes

40 Body density= Body weight Body volume %body fat=(495/body density) - 450

41 Skinfold Thickness Is a common anthropometric method to estimate total body fat content.

42 Bioelectrical impedance Estimate body fat content by sending a painless, low energy electrical current through the body.

43 Dual energy X-ray absorptiometry(dexa) Is considered the most accurate way to determine body fat(1 to 4% error margin) Expensive and not widely available.

44 3- Assessing Body Fat Distribution Upper-body fat storage, as measured by a waist circumference greater than 40 inches (102 cm)(men) or 35 inches(88cm) (women), increases the risks of hypertension, cardiovascular disease, and type 2 diabetes more than does lower-body fat storage.

45 3- Assessing Body Fat Distribution Body fat stored primarily in the upper-body (android) form brings higher risks of ill health associated with obesity than does lower-body (gynoid) fat. The women s waist circumference of 44 inches indicate that the man has upper-body fat distribution but the women does not, based on a cutoff of 35 inches for women and 40 inches for men.

46 Factors Affecting Body Weight and 1- Role of Genetics Composition Research suggests that genes account for up to 40 to 70% of weight differences between people. The genes may be those that determine body type, metabolic rate, and the factors that affect hunger and satiety. Some individuals are thought to have a genetic predisposition to obesity because they inherit a thrifty metabolism. The set-point theory proposes that humans have a genetically predetermined body weight or body fat content, which the body closely regulates.

47 Factors Affecting Body Weight and Composition 2- Role of environment: Environmental factors have important effects on what we eat. Environmental factors, including food availability and preferences, food marketing, social networks, culture, education, lifestyle, health concerns, and income all of which can affect calorie intake and weight gain. 3- Genetic and environmental synergy These factors may define when eating is appropriate, what is preferable to eat, and how much food should be eaten. Even though our genetic backgrounds have a strong influence on body weight and composition, genes are not destiny both nature and nurture are involved.

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49 4- Diseases and disorders Body weight and fatness can be affected by certain diseases, hormonal abnormalities, rare genetic disorders, and psychological disturbances. For instance, cancer, AIDS, hyperthyroidism, Marfan syndrome, and anorexia nervosa tend to cause a person to have limited fat store. Avery small percentage of obesity cases are caused by brain tumors, ovarian cysts, hypothyroidism, and congenital syndromes, such as Prader-Willi syndrome Marfan syndrome Genetic disorder affecting muscles and skeleton, characterized by tallness, long arms, and little subcutaneous fat. Some medical historians speculate that Abraham Lincoln suffered from Marfan syndrome. Prader-Willi syndrome Genetic disorder characterized by shortness, mental retardation, and uncontrolled appetite, caused by a dysfunction of the nervous system, leading to extreme obesity.

50 Treatment of Overweight and Obesity A sound weight loss program emphasizes a wide variety of low-energy- density foods; adapts to the dieter s habits; consists of readily obtainable foods; strives to change poor eating habits; stresses regular physical activity; and stipulates the participation of a physician if weight is to be lost rapidly or if the person is over the age of 40(men) or 50 (women) years and plans to perform substantially greater physical activity than usual.

51 Treatment of Overweight and Obesity Characteristics of a sound weight-loss diet. The body makes numerous physiological adjustments during times of underfeeding or overfeeding that resist weight change. This compensation is most pronounced during times of underfeeding and is why slow, steady, weight loss is advocated.

52 Treatment of Overweight and Obesity A sound weight-loss program should include 3 key components 1. Control of energy intake 2. Regular physical activity 3. Control of problem behaviors

53 The key to weight loss and maintenance can be thought of as a triangle, in which the 3 corners consist of controlling energy intake, performing regular physical activity, and controlling problem behaviors. The 3 corners of the triangle support each otherwithout 1 corner, the triangle becomes incomplete.

54 1. Control of energy intake A pound of adipose tissue contains about 3500 kcal. Thus, if energy output exceeds intake by about 500 kcal per day, a pound of adipose tissue can be lost per week. Using energy density as a Guide to food selection helps Individuals consume foods that health professionals recommend--fruits, vegetables, Legumes, low-fat dairy products, and whole grains.

55 Meal replacement formulas to replace a meal or snack are appropriate to use once or twice a day, if one desires. These are not a magic bullet for weight loss, but they have been shown to help some people control calorie intake.

56 2. Regular physical activity Physical activity as part of a weight-loss program should be focused on duration, rather than intensity. Behavior modification is a vital part of a weight-loss program because the dieter may have many habits that discourage weight maintenance.

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58 3. Control of problem behaviors Controlling of energy intake and increasing physical activity also means modifying problem behaviors. Key behavior modification techniques: Chain-breaking Stimulus control Cognitive restructuring Contingency management Self-monitoring

59 Steps for modifying behaviors that promote weight loss and maintenance

60 Weight-loss maintenance There are 4 behaviors for successful maintainers 1. Eat a low-fat, high-carbohydrate diet. 2. Eat breakfast at least 4 days a week. 3. Self-monitor by regularly weighing oneself and keeping a food journal. 4. Have a physical activity plan.

61 Fad Diets Many fad diet promise rapid weight loss; however, these diets are not designed for permanent weight loss. Low-carbohydrate diets work in the short run because they limit total food intake; however, long-term studies have shown that the weight generally returns in about a year.

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63 Fad Diets Weight loss drugs are reserved for those who are obese or have weight related problems, and they should be administered under close physician supervision.

64 Fad Diets The treatments for sever obesity include surgery to reduce stomach volume to approximately 1 oz. (30 ml) and very-low calorie diets containing 400 to 800 kcal/day. Both of these measures should be reserved for people who have failed at more conservative approaches to weight loss. They also require close medical supervision.

65 The most common forms of gastroplasty for treating sever obesity. The gastric bypass is the most effective method. In banded gastroplasty, the band prevents expansion of the outlet for the stomach pouch.

66 Under weight can be caused by a variety of factors, such as excessive physical activity and genetic background. Sometimes requires medical attention. A physician should be consulted first to rule out underlying disease. The under weight person may need to increase portion sizes and include energydense foods in the diet.

67 Eating Disorders Anorexia nervosa Bulimia nervosa Eating disorders not otherwise specified (EDNOS) Prevention of eating disorders