Metabolism Lec 2 Nutrition Theory PDF

Nutrition & Whole Body Metabolism Nutrition & body weight • • • • Overview of nutrient metabolism Metabolic energy Metabolic rate Nutritional requirements Metabolism Module Dr Shara K Nizamaddin Week 2 Nov 13, 2023 [email protected] 1 Learning Objectives (LO) • Define and give app...

Nutrition & Whole Body Metabolism Nutrition & body weight • • • • Overview of nutrient metabolism Metabolic energy Metabolic rate Nutritional requirements Metabolism Module Dr Shara K Nizamaddin Week 2 Nov 13, 2023 [email protected] 1 Learning Objectives (LO) • Define and give approximate values to the components of your daily energy expenditure. • List the essential components of the diet and explain why they are essential. • Explain the clinical consequences of protein and energy deficiency in human. ‘MUST assessment’ • Determine the body mass index of a patient and interpret the value. • Define obesity and describe the factors involved in the regulation of body weight. 2 Energy Is the capacity to do work It is required to perform different types of work in our body: • Biosynthetic (synthesis of cellular components) • Transport work across cell membrane (uptake of nutrients) • Mechanical work (muscle contraction) • Electrical work (nervous conduction) • Osmotic work (kidney) Unit of Energy The Joule (J) is the unit of energy now widely used, but term calorie (1 cal = 4.184 Joules) is more generally understood by patients. 1 kJ = 1,000 Joules. 1 kcal =1,000 calories. 3 Energy exists in many forms, & they are all inter-convertible : • Thermal (heat) • Light • Mechanical • Electrical • Osmotic • Chemical Chemical bond energy is used to drive the energy-requiring activities in the cells of the human body 4 Chemical bond energy • Is a form of potential (stored) energy and making or breaking chemical bonds involves energy changes. • All chemical reactions involve breaking and formation of chemical bonds. • Reactions where more energy is released than used are exergonic • Reactions where more energy is used than released are endergonic 5 Coupling •Metabolism is all about coupling the energy released by exergonic reactions to that needed for endergonic reactions • Needs an intermediate process –The ATP/ADP cycle • ATP is a form of circulating energy currency in cells. 6 • Chemical bond energy in fuel molecules is released by oxidation • Some of this energy is conserved by the formation of adenosine triphosphate (ATP) from adenosine diphosphate (ADP) and phosphate (Pi) • Remainder is lost as heat. • Controlled release of energy from ATP in cells (ATP-ADP cycle) is used to perform biological work such as movement, membrane transport and biosynthesis. 7 Metabolism: Is the processes which derive energy and raw materials from food and use them to support: • repair • growth • activity of the tissues of the body Metabolism is either: Catabolism –Breaks down large molecules to small molecules to release Energy OR Anabolism –Uses Energy to make molecules for growth and maintenance 8 Daily Energy Expenditure Assuming moderate physical activity the daily energy expenditure of a 70kg adult male would be 12,000kJ and that of a 58kg adult female 9,500kJ. This daily energy expenditure has three components: i. Energy to support our basal metabolism-basal metabolic rate (BMR) ii. Energy for voluntary physical activities iii. Energy required to process the food we eat (diet-induced thermogenesis) 9 i) Basal Metabolic Rate (BMR) BMR is the rate at which the body expends energy (calories) to maintain essential life functions- functioning of various tissues of the body at physical, digestive, & emotional REST So it is a measure of the basal energy required to maintain: Ø Body temperature Ø Cells Ø Ion transport Ø Function of organs The major tissues contributing to BMR are: • Skeletal muscle about 30% of BMR • Liver 20% • Brain 20% • Heart 10% • Other 20% A recommended 2,100-kcal diet consisting of: 58% carbohydrate, 12% protein, and 30% fat content: 305 g of carbohydrate • 0.58 × 2,100 kcal = 1,218 kcal • 1,218 kcal/4 kcal/g = 305 g (1 cal = 4.184 Joules) 63 g of protein • 0.12 × 2,100 = 252 kcal • 252 kcal/4 kcal/g = 63 g 70 g of fat • 0.30 × 2,100 = 630 kcal • 630 kcal/9 kcal/g = 70 g 11 How to estimate BMR A very rough estimate of BMR (in kJ/24hr), in individuals who are not obese, may be obtained by: multiplying the body weight in kg by 100 BMR = weight in kg* 100 e.g In an adult, 70 kg male. 58kg female BMR= 7,000kJ BMR =5,800kJ Although BMR is related mainly to body wight, many other factors affect it. It is mainly controlled by thyroid hormone 12 Factors affecting BMR: • Mainly body size (surface area) • Gender (male BMR higher than female): women has more adipose tissue that’s less metabolically active than lean tissue. • Temperature: the BMR increase by ~ 10% for every 1⁰C increase in body temperature. (in case of fever) • Endocrine status (increases by Hyperthyroidism) • Reproductive hormones (increases in pregnancy and lactation) H.W/ Why fever or any change of body temperature increases BMR? ii) Voluntary Physical Activity In addition to BMR ,the energy required by skeletal and cardiac muscle for voluntary physical activity contributes to our daily energy expenditure. •Very rough estimate of total daily energy required for physical activity can be made using the following values: –Sedentary person –Moderate activity –Very active 30% of BMR(30 kJ/kg/d) 65% of BMR (65kJ/kg/d) 100% of BMR(100kJ/kg/d) 14 iii) Diet-Induced Thermogenesis (DIT) Thermic Effect of Feeding • DIT is energy dissipated as heat after a meal • The ingestion of nutrients causes an obligatory increase in heat production by the body as a result of the metabolic costs of digestion, absorption, metabolism, and storage of nutrients • Metabolic rate increases after food ingestion • Thus, our daily energy expenditure includes a component related to processing food we eat- That energy is equal to ~10% of the energy content of the ingested food. 15 Calculations of Daily Energy Expenditure • The total daily energy expenditure (TDEE) is usually calculated as the sum of: BMR (weight in kg* 100)+ Energy required for Voluntary Physical Activity + 10% of the energy content of the ingested food Thermic Effect of Feeding H.W/ Calculate your approximate daily energy expenditure 16 Nutrition We eat about 500 Kg of food a year, that contains: 1-Macronutrient, form the main bulk of food: Ø Carbohydrates -- main source of immediate energy+ recognition Ø Fats – long term source of energy+ steroid hormones Ø Proteins – structure, enzyme, proteins, hormones, long term source of energy .. 2- Micronutrients, required in small amounts, are essential for speeding chemical reactions: Ø Vitamins Ø Minerals 3- Water: essential-hydration 17 Upon digestion, which convert the nutrient into their smaller units, nutrient will be absorbed and inter blood circulation then to tissues and cells In Blood • Blood is the body fluid in the circulatory system, contains many chemicals: –Nutrients from diet on way to tissues for: Utilization, Storage, Inter-conversion –Nutrients released from storage on way to utilization elsewhere –Materials produced in cells for blood itself Proteins, clotting factors etc –Waste products from tissues on way to excretion 18 In Tissues Tissue Storage •Kidney No •Liver Yes •Adipose tissue Yes •Skeletal muscle Yes •Red blood cells No •Heart muscle No •Brain No Interconversion Yes Yes No No No No No Utilization Yes Yes Yes Yes Yes Yes Yes 19 Clinically important cell nutrients and waste products that can be measured in biological samples Note: the normal ranges are NOT REQUIRED from you 20 An adequate diet is one which contains: • Sufficient fat (lipid) and carbohydrate to satisfy the body's energy requirement • Provides the minimal amounts of protein, vitamins, minerals and water to prevent deficiency. To maintain our body weight we must stay in energy balance i.e. the energy in the food we eat must match our energy consumption over time 21 Recommended Dietary Allowances (RDA) Is average daily level of intake sufficient to meet the nutrient requirements of nearly all (97–98%) healthy individuals; often used to plan nutritionally adequate diets for individuals. It depend on: • Age, gender, and level of physical activity • Increased in pregnancy & lactation • minimum required to prevent symptoms & signs of deficiency 22 Energy available from foods Energy available: (1 cal = 4.184 Joules) –Carbohydrate –Protein –Lipid –Alcohol 17 kJ/gm 17 kJ/gm 37 kJ/gm 29 kJ/gm 4 kcal/gm 4 kcal/gm 9 kcal/gm 7 kcal/gm Fat & carbohydrate are the major energy containing components of the diet. We can, however, derive energy from the metabolism of proteins and from alcohol. 23 Overall Nutritional requirements: Supply of energy and essential raw materials ü Carbohydrate: mostly supplies energy ü Fat: energy and essential fatty acids ü Protein: energy and amino acids (some a.a cannot be made) ü Vitamins & minerals: essential-deficiency or excess in diet might lead to disease ü Water: maintains hydration (2 liter/day recommended) ü Fiber: non-digestible plant materials such as cellulose is necessary for normal Gastrointestinal (GI) function H.W 1. What is the potential side effects of low-fat or free fat diet? 2. Why vegetarians and vegans might need to take supplement? 3. Why we should increases unsaturated fat and decreases saturated fat in our diet? 24 Q/ After a routine physical exam and blood work, a woman with a normal weight for her height was advised that her lipid profile showed an elevation of blood triglycerides. The doctor advises the patient to lower fat consumption which disappoints her since she avidly consumes whole milk. The woman consults a nutritionist, who states that whole milk is 3.5% fat, which corresponds to approximately 11 g of fat in 250ml serving. If she switches to drinking skim milk (nonfat), approximately how many additional grams of carbohydrates should she consume to make up for the loss of fat in the 250ml serving? a) 5 grams b) 15 grams c) 25 grams d) 35 grams 25 Energy Intake & Body weight: • If energy intake equals expenditure, the body weight will be stable • If intake exceeds expenditure, the energy stores will increase • If expenditure exceed intake : -first energy stores will deplete -then other body components (principally protein) will be utilized to provide energy Body composition (Body weight) Carbohydrate (kg) Lipid (kg) Protein (kg) Mineral Water 70 kg man 1 11 11 4 42 100 kg man 1 39 12 4 43 Energy Stores Very short term stores of energy rich molecules in muscle –few seconds •Carbohydrate stores for immediate use as glycogen –0.1 kg in liver –0.3 kg in muscle –Don’t last long -minutes or hours depending on activity. Long term stores in adipose tissue as lipid –11x37000kJ -About 40 days Muscle protein can be converted to carbohydrate (last options of energy, as its main function is structure) ––By Gluconeogenesis __About 6 kg available __ Support tissues (lipids cannot) 27 Ideal body weight A lot of evidence to suggest that both excessive body weight, & being underweight are associated with an early death For each of us there is an ideal or desirable weight that depends upon our height and the general shape of our body Body Mass Index (BMI): Weight in kg divided by height in meter squared BMI= Weight in Kg/(height)2 in m Male MBI FemaleBMI <20 <19 Underweight 20 -25 19 -24 Desirable weight 26-30 25 -30 Overweight >30 >30 Obese 28 Overweight/Obesity -A major potentially preventable cause of death in developed world -Factors may influence tendency to put on weight are: genetic, drug therapy, endocrine disorders- but its mostly imbalance between energy intake and energy expenditure. Obesity is associated with: –Diabetes –Hypertension –Heart disease --Stroke –Gall bladder disease Diet Analysis The Eatwell Guide UK) https://www.nhs.uk/live-well/eat-well/food-guidelines-and-foodlabels/the-eatwell-guide/ Diet Analysis- MyPlate (USA) • https://www.myplate.gov 30 Malnutrition: A major potentially preventable cause of death in developing world Protein energy malunion (PEM) in children: •Marasmus is the type of protein-energy malnutrition most commonly seen in children under the age of 5, due to low calorie intake •Kwashiorkor occurs typically in a young child displaced from breastfeeding by a new baby and fed a diet with very low protein content 31 Adult malnutrition screening https://www.bapen.org.uk/screening-and-must/must-calculator