Energy Metabolism and BMR Energy Metabolism Metabolism refers

Energy Metabolism and BMR

Energy: Metabolism �‘Metabolism refers to chemical process that occur in the body that are necessary to maintain life. ’ (Magee & Oliver 2010) �Metabolism involves two key processes: Catabolism � Substances are broken down into simpler substances. For example, carbohydrate is converted to glucose. Anabolism � Larger molecules or structures are built from smaller ones. For example, proteins build body tissue. �Energy is released during catabolic reactions to create (adenosine triphosphate)

Carbohydrate Metabolism Carbohydrates from food Monosaccharides Blood glucose Cellular use Excess stored as glycogen or converted to fat and stored ATP Energy Stores broken down to glucose if needed for ATP

Lipid Metabolism Lipids from food Converted to glycerol and fatty acids Metabolised in liver to acetic acid Cellular Use Cell membranes Insulation ATP if not enough glucose

Protein Metabolism Protein Amino Acids Cellular Use Build and repair body tissue ATP only if inadequate glucose and fats. Least preferred option

Energy: Storage and Balance �Storage of metabolised food is essential for times of famine and when the body requires great energy output. �Storage occurs in cells in the form of either glycogen or triglycerides. �If the body’s energy needs are in balance, energy consumption equals energy expenditure.

Energy: Storage and Balance �The body requires energy for: Maintaining body temperature (heat energy) Brain and nerve transmission (electrical) Movement (mechanical) Digestion and Metabolism (chemical energy) �The energy is easily transferred from one form to another depending on the body’s requirements.

Basal Metabolic Rate (BMR) �Only 30% of energy intake is used for physical activity. �Remaining 70% is used for all the other metabolic processes that occur in the body. �Basal energy is the minimum amount of energy used to maintain normal body temperature and muscle tone, to keep the heart beating and all vital organs functioning. �The rate at which energy is needed for these metabolic processes is called the Basal Metabolic Rate.

How to calculate BMR? Females Males 1 kg of body weight burns roughly 0. 9 of a calorie per hour. 1 kg of body weight burns roughly 1. 0 calorie per hour. 70 kg X 0. 9 X 24 hours = 1512 calories per day 80 kg X 1. 0 X 24 hours = 1920 calories per day To convert to kilojoules Calories X 4. 184 (4. 2) = 6350 kj/per day To convert to kilojoules Calories X 4. 184 (4. 2) = 8064 kj/per day Turn to p 52 and complete activity 11.

Influences on BMR �Body size The larger the body the greater the BMR due to increased energy demands �Body fat Fatty tissues have a lower BMR than muscle tissue. Therefore, greater lean body tissue increases your metabolic rate, because it is an active tissue that burn kilojoules at a faster rate.

Influences on BMR �Hormones People with an overactive thyroid have a higher BMR. �Illness Increased BMR as the body works harder to fight infection �Fasting Reduces BMR, because the body conserves energy to keep vital organs functioning.

Influences on BMR �Drugs Caffeine and nicotine increase BMR Anti-Depressants, social and prescription drugs reduce BMR �Exercise BMR increases during exercise. BMR remains high during intense prolonged activity. �Gender Males have an elevated BMR than females

Influences on BMR �Climate Cold temperatures increase BMR given the body uses energy to stabilise body temperature. �Age Decreases with age due to less activity and reduce lean tissue

Energy Balance �To identify a person’s energy balance you must calculate energy intake and expenditure. If intake is higher than expenditure a person will store energy. If intake is lower than expenditure a person will burn energy. �To calculate daily energy intake list all the food and beverages consumed. Using a food kilojoule table work out their values. �Energy Expenditure for the day = BMR + thermic effect + exercise Calculate BMR Take into account thermic effects of food (10%) Work out the kilojoule expenditure for various activities.

Thermic Effect of Food �‘…the energy used in digestion, absorption, metabolism and the storage of ingested nutrients. ’ �Thermic effect is estimated at 10% of energy intake.

Energy Expenditure Calculation Example (p 53) � 73 kg female consuming 8500 k. J walked for 30 minutes using 462 k. J and cycled for 60 minutes using 1344 k. J �BMR = 73 X 0. 9 X 24 = 1576. 8 calories = 1576. 8 x 4. 2 = 6623 kj �Thermic effect =. 10 X 8500 kj = 850 kj �Energy Expenditure for the day = 6623 + 850 + 1806 = 9279 kj �Energy balance = Intake – Expenditure � 8500 kj – 9279 kj= 779 kj

Your Turn – Calculate Energy Balance � 68 kg male consuming 11000 kjwho jogged for 30 minutes (300 calories) and cycled for 1. 5 hours (420 calories) BMR = 68 x 1. 0 x 24 = 1632 calories = 1632 x 4. 2 = 6854 kj Thermic Effect =. 10 x 11000 kj = 1100 kj Energy Expenditure = 6854 + 1100 + 1260 +1764= 10978 kj Energy Balance = 11 000 – 10978 = 22 kj

Your Turn – Calculate Energy Balance �Female 62 kg consuming 6985 k. J and burning 486 calories in daily activities. BMR = 62 kg x 0. 9 x 24 = 1339. 2 x 4. 2 = 5625 kj Thermic Effect = 6985 x. 10 = 699 kj Energy Expenditure = 5625 + 699 + 2041 = 8365 kj Energy Balance = 6985 – 8365 = - 1380 kj

Body Mass Index (BMI) �BMI is a measure of weight for height. �BMI does not distinguish between weight due to fat or weight due to muscle. �BMI data developed based on data from Anglo-Saxon background; thus, height, weight and fat distribution among different ethnic groups is not taken into account.

BMI Women Men <18 <19 Healthy weight 19 -24 20 -25 Overweight 25 -30 26 -30 >30 Underweight Obese