Energy Balance Past Paper PDF - CBF 2023-2024

Metabolic Rate Energy Input And Output Energy Balance Code: CBF-103 By Dr. Rasha Mohammed Ali Lecturer of Medical Physiology, Faculty of Medicine, Assiut University At the end...

Metabolic Rate Energy Input And Output Energy Balance Code: CBF-103 By Dr. Rasha Mohammed Ali Lecturer of Medical Physiology, Faculty of Medicine, Assiut University At the end of the lecture, the student will be able to: Briefly describe energy balance. Understand the respiratory quotient and explain its significance. Understand the basal metabolic rate and the factors affecting it. 2  Metabolism Definition: All chemical reactions & energy transformations that occur inside the body. It include 2 processes : 1. Anabolism Definition: It is the process of synthesis of carbohydrate, fat, protein & high energy rich phosphate compounds from simpler modules by processes which take up rather than liberate energy. 2. Catabolism Definition: It is the process of breakdown of fat, carbohydrate (CHO), protein into small ones with liberation of energy. 3 Energy balance Positive energy balance: More anabolism occur than normal. The energy stores increase. In obese persons &in growing children. Negative energy balance: More catabolism than normal. The body weight decreases. In undernutrition & starvation. 4  The Calorie kilocalorie or C or K cal Definition: It is the amount of heat energy necessary to raise the temperature of one kilogram water 1°C (from 15°C to 16°C). 1 C=1000 c. 5  Physiological heat values of food Definition: It's the amount of heat liberated from oxidation of foodstuffs inside the body. (4.1C for 1gm CHO & 9.3C for 1gm fat and 4.1C for 1gm protein). Physical heat values of food Definition: It is the amount of heat liberated from oxidation of food stuffs outside the body.(4.1C for 1gm CHO & 9.3C for 1gm fat and 5.3C for 1gm protein). They are the same CHO and fat because both substances are completely oxidized to Co2 and H2o inside or outside the body. In case of protein the physiological heat value is less than the physical value because it is not completely oxidized in the body and form some nitrogenous compounds which is exerted in urine  R.Q) Significance of R.Q: 1-Index of the substance that has been oxidized during time of estimation: If this substance is CHO, the R. Q will be 1. C6 H12 O6 +6O2 → 6 CO2+ 6 H2O R.Q=6/6=1 The R.Q will be less than 0.7 for fat and 0.8 for protein. 2 C51 H 98 O 2+ 145 O 2 →102 CO2+ 98 H2O R.Q=102/145=0.7 (tripalmitin) Normally, the R.Q of the mixed diet is 0.85 and that of the brain tissue is about 1 (0.97-0.99) indicate7 s that CHO is the only fuel utilized by the nervous system. 2.It indicates transformation of one food substance into another in the body : CHO are transformed to fat, the R.Q rises above 1. This is because a substance rich in O2 (CHO) is transformed into a substance poor in O2 (fat). The opposite occur if fat are transformed into CHO (gluconeogenesis). 3. Estimation of R.Q is used in determining the energy equivalent (heat value) of O 2 : It is the amount of heat in calorie produced when one liter of O 2 is used to oxidize different mixtures of food stuffs in the body. This is greatly helpful in calculation of metabolic rate by indirect colorimeter.  Factors affecting the R.Q: Factors increasing the Factors that decreasing the R.Q above unity: R.Q below unity: Transformation of CHO Transformation of fat into into fat. CHO. Hyperventilation. During recovery period During muscular exercise. following muscular exercise. Metabolic acidosis. Metabolic alkalosis. Fever. Diabetes mellitus. Starvation.  The Excess R.Q Definition: It is R.Q of the excess metabolism that occur during the exercise period and the following recovery period. It is calculated as: 𝐂𝐨𝟐 𝐩𝐫𝐨𝐝𝐮𝐜𝐞𝐝 𝐝𝐮𝐫𝐢𝐧𝐠 𝐞𝐱𝐞𝐫𝐜𝐢𝐬𝐞 & 𝐫𝐞𝐜𝐨𝐯𝐞𝐫𝐲 − 𝐂𝐨𝟐 𝐩𝐫𝐨𝐝𝐮𝐜𝐞𝐝 𝐝𝐮𝐫𝐢𝐧𝐠 𝐬𝐢𝐦𝐢𝐥𝐚𝐫 𝐩𝐞𝐫𝐢𝐨𝐝 𝐨𝐟 𝐫𝐞𝐬𝐭 / 𝐎𝟐 𝐜𝐨𝐧𝐬𝐮𝐦𝐞𝐝 𝐝𝐮𝐫𝐢𝐧𝐠 𝐞𝐱𝐞𝐫𝐜𝐢𝐬𝐞 & 𝐫𝐞𝐜𝐨𝐯𝐞𝐫𝐲 − 𝐎𝟐 𝐜𝐨𝐧𝐬𝐮𝐦𝐞𝐝 𝐝𝐮𝐫𝐢𝐧𝐠 𝐬𝐢𝐦𝐢𝐥𝐚𝐫 𝐩𝐞𝐫𝐢𝐨𝐝 𝐨𝐟 𝐫𝐞𝐬𝐭 If it's around unity, it indicates a short exercise in which CHO mainly utilized. If it's below unity, it indicates an exercise for long time in which mainly lipids are utilized.  The metabolic rate It is the energy output per unit of time. It is measured by special technique called calorimetry 10 Basal Metabolic rate (BMR) Definition: Rate of energy expenditure or heat produced (C) in a specific time (hour) per meter square surface area (m2) under standard basal conditions. (i.e. When a person is at complete rest, considerable energy is required to perform all the chemical reactions of the body). This minimum level of energy required to exist is called BMR. It is measured under the following standard basal conditions: 1- The person must not have eaten food for at least 12 hours. 2- Complete physical and mental rest for at least 30 minutes (The BMR is determined after a night of restful sleep , all psychic and physical factors that cause excitement must be eliminated and no physical activity is performed for at least 1 hour before the test). 3-The temperature of surrounding air must be comfortable (20-25C). Methods of determination: while the subject in basal conditions. 1- Direct Calorimetry. 2- Commonly by indirect calorimetry (using metabolic tables). The energy output is calculated /hour, then divided by the body surface area which can be obtained from DuBois chart Significance (importance): The BMR investigates the metabolic rate in absence of the major factors affecting it (muscular activity, emotion, food intake & environmental temperature) and is related to the body surface area to eliminate the effect of body size. The energy expenditure due to vital body activities (heart beating, respiratory movements, activity of liver, kidneys , brain ,etc.) Standard BMR is usually expressed as: kilocalories per square meter surface area per hour. For an adult it is : 40 Kc/m2/hour =40 C/m2/hour. But clinically expressed as a percentage of increase or decrease from the normal standard value for the subject e.g. if BMR is 60C/m2/ hour; it is expressed as +50%(20/40 x100). The BMR is considered normal if it is within ± 15%of the standard value for his age and sex. 13  Factors affecting BMR I- Physiological factors: 1) Age: Newly born infants: 25 kcal/m2/h, so infants are greatly susceptible to cold. At age of 20 years: 40 cal/m2/h. After 20 years: the BMR decreases at a rate of 1 kcal for each 10 years due to loss of muscle mass and its replacement with adipose tissue that has a lower rate of catabolism. 2) Sex: BMR is lower in women compared with men, due to their lower percentage of muscle mass and higher percentage of adipose tissue. 3) Physical habits: Athletes have a higher BMR than those having sedentary life. Training increases the bulk of active muscles and reduces the store of fat. 4) Dietetic habits: High p1r4otein diet raises the BMR by 10% more than eating carbohydrates. 5) Sleep: The metabolic rate decreases 10-15 % below normal during sleep. This fall is due to decreased tone of the skeletal musculature and decreased activity of the central nervous system. 6) Climate: People living in cold regions have BMR 10 % higher than those of persons living in tropical regions. This is due to adaptation of the thyroid gland (more secretion in cold climates and less secretion in hot climates) 7) Pregnancy, lactation and menstruation: BMR is more in women in those conditions than normal standard. In pregnancy; the BMR increases due to: A. Increase thyroid activity. B. Additional metabolic activity of the fetus. 15 8) Race: Affect BMR as Orientals and Africans have lower BMR than Europeans. 9) Anxiety and tension: They increase BMR because they are associated with increase in epinephrine secretion and muscle tone. II- Pathological factors: Factors that increase BMR: 1 Hyperthyroidism: raises BMR by about 50-100% above normal. Thyroxin increases the rates of the chemical reactions of many cells in the body and therefore increases metabolic rate. 2 Hyperpituitarism: growth hormone can increase the metabolic rate 15-20% as a result of direct stimulation of cellular16metabolism. 3 Hyperadrenalism: Tumors of the suprarenal medulla raises BMR by about 150%. This also occur with secretion of adrenaline. 4 Fever: It increases the chemical reactions of the body by an average of about 120% for every 10°C rise in temperature. 5 Anemia &leukemia. 6 Heart failure accompanied by dyspnea II- Pathological factors: Factors that decrease BMR: 1.Hypothyroidism 2. 3. Hypocorticism. Hypopituitarism. 5. Starvation. 4. Hypothermia. 6. Shock. 17  Specific dynamic action (SDA) Definition: power of food to stimulate metabolic rate. It is the amount of energy expenditure above basal metabolic rate due to the cost of processing of food for use and storage It is an obligatory increase in the metabolic rate that occurs after recent ingestion of food (which about 1 hour after food intake, reach a maximum within 4-5 hours and last for 12-14 hours). Factors affecting the SDA: 1. Type of food: CHO:6% ,fat :4% ,protein :30% ,mixed diet :10% 2. Amount of food: The greater the protein ingested, the more the increase in metabolic rate (advised in treatment of obesity). 3. Environmental temperature: The excess heat produced as a result of SDA is completely lost from the body at atmospheric temperature 33 °C. Causes of SDA SDA is not mainly due to energy expended during digestion and absorption of food (Since I.V. administration of food also produces SDA). It is due to metabolic reaction in the liver (not due to digestion or absorption of food. It is a waste heat except during exposure to cold (keep your temperature within normal)