Metabolism of Nutrients and Energy Balance PDF

Unit III: Metabolism of Nutrients and Energy Balance Outline :  the body deals with energy in take above or below requirements.  Food energy value (metabolism|).  The body of measures related below and their strength and weakness.  Body mass index (BMI).  Body Circumference mea...

Unit III: Metabolism of Nutrients and Energy Balance Outline :  the body deals with energy in take above or below requirements.  Food energy value (metabolism|).  The body of measures related below and their strength and weakness.  Body mass index (BMI).  Body Circumference measurement. Learning objectives At the end of this chapter, the student should be able to: 1. Define concepts 2. Discuss the energy balance. 3. Describe the factors which Affect Basal Metabolic Rate. 4. Discuss the term of Body weight and body mass standards. 5. Outline the classification of overweight and obesity by BMI and arm circumference. 6. Identify examples of energy requirements for people according to their daily activities and nature of work. Energy  Metabolic rate refers to the rate of heat liberation during chemical reactions; it is expressed in units called calories.  A calorie is the quantity of heat required to raise the temperature of 1 gram of water 1_C; it is used to express the quantity of energy released from different foods or expended by different functional processes of the body. 21 University of Mosul / College of Nursing Nutrition   Because a large quantity of energy is released during metabolism, the energy is expressed in terms of kilocalories (kcal), each of which is equivalent to 1000 calories.  The basal metabolic rate(BMR) refers to the energy needed to maintain essential physiological functions, such as respiration, circulation, and muscle tone, when a person is at complete rest both physically and mentally. Energy Balance  Energy balance is the relationship between the energy derived from food and the energy used by the body.  The body obtains energy in the form of calories from carbohydrates, protein, and fat.  The body uses energy for voluntary activities such as walking and talking and for involuntary activities such as breathing and secreting enzymes.  A person's energy balance is determined by comparing his or her energy intake with energy output. Energy Intake  The amount of energy that nutrients or foods supply to the body is their caloric value. A calorie (c, cal, kcal)is a unit of heat energy.  A small calorie (c, cal)is the amount of heat required to raise the temperature of I gram of water 1°C. This unit of measure is used in chemistry and physics. 22 University of Mosul / College of Nursing Nutrition   A large calorie (Calorie. kilocalorie, kcal)is the amount of heat energy required to raise the temperature of 1 gram of water 15 to 16°C.  The energy liberated from the metabolism of food has been determined to be: 1 gram of carbohydrates = 4 Calories 1 gram of protein = 4 Calories 1 gram of Fat = 9 Calories Energy Output  Metabolism refers to all biochemical and physiologic processes by which the body grows and maintains itself.  Metabolic rate is normally expressed in terms of the rate of heat liberated during these chemical reactions.  The basal metabolic rate (BMR) is the rate at which the body metabolizes food to maintain the energy requirements of a person who is awake and at rest.  The energy in food maintains the basal metabolic rate of the body and provides energy for activities such as running and walking. Factors which Affect Basal Metabolic Rate (BMR) 1. Body surface area  This is a reflection of height and weight.  The greater the body surface area factor. the higher the BMR. 23 University of Mosul / College of Nursing Nutrition   Tall, thin people have higher BMRs If we compare a tall person with a short person of equal weight, then if they both follow a diet calorie controlled to maintain the weight of the taller person, the shorter person may gain up to 15 pounds in a year. 2. Sex: Males average a higher BMR because of a greater proportion of lean body mass 3. Body temperature: Fever, for example, increases BMR. 4. Hormones: Thyroid hormones have a stimulatory effect on the metabolism of the body and, therefore, BMR. Thus BMR is raised in hyperthyroidism and reduced in hypothyroidism. 5. Age: Metabolic rate declines with age. In infants and children BMR is higher and in adults it is less 6. Diet: Starvation or serious abrupt calorie reduction can dramatically reduce BMR (30%). Restrictive low-calorie weight loss diets may cause BMR to drop as much as 20%. 7. Pregnancy/breast feeding: these increase metabolic rate 8. Environment: In cold climates, the BMR is higher compared to warm climates. 9. Rapid growth and/or development: infancy, growth spurts, healing after illness or injury. 10. Disease states: BMR is higher in cardiac failure, leukemia, and hypertension. It is marginally lowered in Addison's disease. 24 University of Mosul / College of Nursing Nutrition  11. Weight. Heavier the weight, the higher BMR. Example: The metabolic rate of obese women is 25 'percent higher than the metabolic rate of thin women. 12. Exercise: Physical exercise not only influences body weight by burning calories, it also helps raise our BMR by building extra-lean tissue. (Lean tissue is more metabolically demanding than fat tissue.) So, we bum more calories even when sleeping. 13. Amount of lean body mass: muscle, liver ,brain, kidney all metabolize at a high rate at rest, and have high energy needs when more active Body weight and body mass standards  Maintaining a healthy or ideal body weight requires a balance between the expenditure of energy and the intake of nutrients.  Generally, when energy requirements of an individual equate with the daily caloric intake, the body weight remains stable.  Ideal body weight (lBW) is the optimal weight recommended for optimal health; however, many health professionals consider the body mass index to be a more reliable indicator of a person's healthy weight.  For people older than 18 years, the body mass index (BMI) is an indicator of changes in body fat stores and whether a person's weight is appropriate for height, and may provide a useful estimate of malnutrition.  However, the results must be used with caution in people who have fluid retention (e.g., ascites or edema), athletes, or elders.  To calculate the BMI. 1. Measure the person's height in meters, e.g., 1.7 m 25 University of Mosul / College of Nursing Nutrition  2. Measure the weight in kilograms, e.g., 72 kg 3. Calculate the BMI using the following formula Weight in kilograms BMI=_______________________ (Height in meters}2 Or 72 kilograms ______________= 24.9 1.7(meters)2 26 University of Mosul / College of Nursing Nutrition Methods of Determining Caloric Needs  The first step in designing a personal nutrition plan for ourselves is to calculate how many calories we burn in a day; our total daily energy expenditure (TDEE).  TDEE is the total number of calories that our body expends in 24 hours, including all activities. Specific Dynamic Action  Ingestion of food is accompanied by an increased rate of heat production. The extra-heat production by the body, over and above the calculated caloric value, when a given food is metabolized by the body, is called as specific dynamic action. Examples :- The energy requirement of a man (age 20 years, BMR=42 Cal/ Sq. meter body surface/hr., body surface area=1.7 sq. m) engaged in light work- The energy demand depends on three important factors: a. Basal metabolic rate b. Physical activity c.Specific dynamic action The food provides energy for:  Basal metabolism (8 hours) 27 University of Mosul / College of Nursing Nutrition   Simple activities: standing, sitting, walking, dressing and writing (8hours).  Professional work: i) light work, ii) moderate work, iii) heavy work iv)very heavy work (8 hours).  Other 10% as SDA. The daily energy requirement is variable which depends on age, sex, and body size.  Sleep-basal level (8 hour) BMR x body surface area x 8 hr. = 42 x 1.7 x 8 = 571 Cal  Simple activities (8 hr.) at basal level = 571 Cal For simple activities at 25 Calories / hr. over basal level 25 x 8 = 200 Cal  For professional work (light work) at basal level = 571 Cal For professional work at 55 Calories/hr. over basal level 55 x 8 = 440 Cal Subtotal = 2353 Extra 10 % for SDA, = 235 Cal Total = 2588 Cal/day The energy requirement of dental student (age 18 years, BMR = 40 Cal/Sq.meter body surface/hr, body surface area = 1.7 sq.m) engaged in moderate work  Sleep-basal level (8 hour) BMR x body surface area x 8 hr. = 40 x 1.7 x 8 = 544 Cal.  Simple activities (8 hr.) at basal level = 544 Cal For simple activities at 28 University of Mosul / College of Nursing Nutrition  25 Calories/hr. over basal level 25 x 8 =200 Cal For professional work (light work) at basal level = 544 Cal For professional work at 75 Calories/hr. over basal level 75 x 8 = 600 Cal Sub total = 2432 Extra 10 % for SDA, = 243 Cal Total =2675 Cal/Day The energy requirement of men (age 25 years, BMR=40 Cal/Sq.meter body surface/hr, body surface area=l.7 sq.m) engaged in heavy work  Sleep- basal level (8 hour) BMR x body surface area x 8 hr. = 40 x 1.7 x 8 = 544 Cal.  Simple activities (8 hr.) at basal level = 544 Cal For simple activities at 25 Calories/hr. over basal level 25 x 8 =200 Cal  For professional work (heavy work) at basal level =544 Cal For professional work at 150 Calories/hr. over basal level 150 x 8 =1200 Cal Subtotal =3032 Cal Extra 10 % for SDA, =303 Cal Total =3335 Cal/Day From the above calculations the reference ranges of Caloric requirements of various types of work for an adult per day is as follows: Light work......... 2100- 2600 Moderate work... 2500-3000 Heavy work....... 3000-3500 Very heavy work 3500-4000 29 University of Mosul / College of Nursing Nutrition