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Chapter 5 47 Energy KEY OBJECTIVES By the end of the chapter, the reader will be able to describe the following: Unit of Energy Measurements of Energy Energy Value of Food Calculation of Energy Requirement for an Individual Energy Requirements for Different Categories of People Energy Balance Energy Requirements by Indians Obesity Energy is the ability to do work. We eat food to supply energy to the body. A body requires energy not only when it is at work but also when it is at rest. Why do we need energy when the body is resting? The body needs energy to carry out its basal requirements like breathing and metabolism and to regulate body functions like temperature and heart rate. This energy is calculated and it is considered to be the energy required for basal metabolism. This energy is called resting energy expenditure (REE). Brain is an organ that uses only glucose for its proper function. Food we eat consists of major nutrients like carbohydrates, proteins and fats. Energy is released by the metabolism of food, which is utilized by the body regularly to maintain life. This continuous process involves many biochemical reactions that include digestion, absorption, synthesis and maintenance of tissues, conduction of nerve impulses and regulation of body temperature.UNIT OF ENERGY The energy present in foods is usually expressed as calories. A calorie is the amount of heat energy required to raise the temperature of 1 mL of water at a standard unit temperature by 1°C. So, the unit of energy is calorie (cal). But, the energy content of foods is usually expressed in kilocalories (kcal); 1 kcal = 1000 cal.
Nutrition and Biochemistry for Nurses48 The amount of heat required to raise the temperature of 1 kg of water by 1°C is defined as 1 kcal. The SI unit of energy is joule. The joule, a unit of energy based on mechanical energy, is defined as the work done by a force of 1 N acting through a distance of 1 m. ENERGY VALUE OF FOOD Carbohydrates are the major source of energy for our body; 1 g of carbohydrates = 4 kcal (17 kJ). Protein is used mainly for the synthesis of tissues, but it is also used as a source of energy; 1 g of protein = 4 kcal (17 kJ). Fat is a concentrated source of energy, as 1 g of fat yields 9 kcal. The energy supplied by the food should be as follows: 60–65% of the total energy should be supplied by carbohydrates mainly by complex carbohydrates. 20–30% of energy should come from proteins. 10–15% of energy should be from fats (saturated fats but mainly from polyunsaturated and monounsaturated fatty acids). ENERGY REQUIREMENTS FOR DIFFERENT CATEGORIES OF PEOPLE The energy requirement of an individual depends on Energy required for basal metabolism (BMR) Thermogenic effect of food Physical activity There should always be a balance between the energy requirement and the energy expenditure to ensure good health and vitality. When the energy requirements for individuals are being considered, their stage of life cycle should also be taken into consideration; stages such as pregnancy and lactation require additional energy. Basal Metabolic Rate BMR is defined as the minimum amount of energy required by a person at complete physical and mental rest and in the postabsorptive state (10–12 hours after the last meal). In the resting state, the energy is expended for regulatory activities and to sustain life processes such as respiration, circulation and regulation of body temperature.
Energy 49Factors affecting BMR Body size and composition: This is associated with heat loss and energy required to maintain lean muscle mass at rest. Body surface area: BMR is directly proportional to body surface area. Higher the body surface area, higher the BMR. This is because the metabolic rate is affected significantly by the amount of heat lost in the atmosphere by evaporation from the skin, the need to maintain body temperature. Age: BMR is higher in infants and young children as compared to adults. It is highest during the periods of rapid growth—the first and the second years of life. Gender: Males have a higher BMR than females. Weather conditions: BMR is higher in cool climates compared to warmer climates. Exercise: BMR increases during exercise. This factor is an important point to note in weight loss as diet alone cannot cause significant weight loss. The ideal way to lose weight is to eat right and perform regular physical activity. Sleep: Sleep decreases BMR by 10% below that of levels measured while the person is awake and reclining. Fever: Rise in body temperature increases the metabolic rate by about 7% for each degree rise in body temperature. Hormones: Thyroxine and norepinephrine are the hormones secreted by the endocrine glands. In hypothyroidism, when the supply of thyroxin is inadequate, the basal metabolism is decreased by 30–50%. In a hyperactive thyroid gland, as in the case of hyperthyroidism, the BMR almost doubles.Units for BMRBMR is usually measured by using Benedict‒Roth apparatus using the indirect calorie method. It is ex-pressed in kilocalories per square metre body surface area per hour (kcal/m2/hour).Calculation of BMRBMR is expressed as per kilogram body weight. Normal BMR of an adult male is 24–26 kcal/kg bodyweight/day. Normal BMR of an adult female is 22–24 kcal/kg body weight/day.Thermic Effect of FoodThermic effect of food- or diet-induced thermogenesis is the consumption of extra energy when the foodis being metabolized by the body or in the process of consumption of that food. Consumption of calorie orfat increases the metabolic rate by about 5% of the total calorie consumption. If the entire food is made up of proteins, the metabolic rate is about 25%. But the food we eat is a combination of major nutrients likecarbohydrates, proteins and fats. Hence, it is generally calculated as 10%.
Nutrition and Biochemistry for Nurses50 Physical Activity Physical activity can be classified as heavy, moderate or sedentary. Heavy: Heavy or strenuous physical activity is the work done by farmers toiling in their field, factory workers, manual labourers and construction workers. Moderate: Work done by housewives and students. Sedentary: Physical activity that involves only a desk job for 8 hours a day like a BPO employee, IT worker, teacher and people in clerical jobs. ENERGY REQUIREMENTS BY INDIANS The ICMR Expert Group of 2009 on nutrient requirement and safe dietary intake of Indians used data on energy requirements of adults and children by using doubly labelled water, i.e. 2H2O18 turnover because this technology measures energy requirements more directly and accurately under normal living conditions. Energy requirements computed by this method are lower than those computed using the dietary intake and factorial method. The reference body weight for Indians was taken as 95th percentile of the body weight of Indians and the physical pattern as surveyed by the National Nutrition Monitoring Bureau (NNMB). Activity Status in Rural India (NNMB) Activity status Men Women Total n % n % n % Sedentary 1349 33.3 2705 62.7 4114 48.6 Moderate 2650 66.5 4282 37 4282 50.6 Heavy 48 1.2 14 0.3 62 0.8 Pooled 4047 100 4411 100 8458 100 n = sample size
Energy 51Recommended Energy Requirement ICMR Expert Group 2009 Age groups Category Requirements Difference from 1989 RDAs (kcal/day) (kcal/day) Sedentary work 2318 –107 Men Moderate work 2727 –148 Heavy work 3485 –315 Sedentary work 1899 +24 Women Moderate work 2234 –9 Heavy work 2854 –71 Pregnant woman +350 +50 Lactating woman +600 +50 0–6 months +520 +120 6–12 months Infants 0–6 months 92 kcal/kg/day –16 kcal/kg/day 6–12 months 79 kcal/kg/day –19 kcal/kg/day Children 1–3 years 1036 –204 4–6 years 1350 –340 7–9 years 1691 –259 Boys 10–12 years 2189 — 13–15 years 2748 +298 16–18 years 3017 +377 Girls 10–12 years 2008 +48 13–15 years 2328 +268 16–18 years 2070 +10Energy requirement is estimated for an average weight gain of 10 kg during pregnancy.Reference Body Weight of Indians Group Age Weight (kg) Infants 0–6 months 5 6–12 months 8 Children 1–3 years 12 4–6 years 18 7–9 years 25 Girls 10–12 years 35.0 13–15 years 46.6 16–18 years 52.1 Boys 10–12 years 34 13–15 years 47 16–18 years 55.5 Men 18–30 years 60.0 Ht = 172 cm BMI = 20.0 Women 18–30 years 55.0 Height = 161 cm BMI = 22.2
Nutrition and Biochemistry for Nurses52 MEASUREMENTS OF ENERGY The amount of energy present in foods or the potential energy in foods can be measured by calorimetry. Direct Calorimetry When a food is oxidized, the amount of heat produced by the oxidation of food is measured by using bomb calorimeter or Atwater Rosa respiration calorimeter. Indirect Calorimetry In this method, the energy released is measured indirectly by the oxygen used up or consumed by food materials. Benedict’s oxycalorimeter, Benedict–Roth respiration apparatus and Douglas bag use indirect calorimetry method. CALCULATION OF ENERGY REQUIREMENT FOR AN INDIVIDUAL Energy requirement can be calculated after taking into consideration the age, sex, physical activity and weight. Method Calculate the energy required for the basal metabolism. For men, 26 kcal/kg body weight For women, 24 kcal/kg body weight Calculate the energy required for physical activity. Add both the requirements. Add 10% for the thermogenesis effect of food. This gives the total energy required by the individual. Sample: Energy requirement of an adult man (70 kg sedentary work) Energy required for BMR = 26 kcal/kg body weight = 70 × 26 = 1820 kcal Energy required for physical activity = (Add 30–40% of BMR) = 40/100 × 1820 = 728 + 1820 = 2548 kcal Additional 10% energy required for thermogenesis = 2548 × 10%= 254 kcal Total energy requirement = 2548 + 254 = 2802 kcal/day The total energy requirement for an adult man of 70 kg doing sedentary work = 2800 kcal/day.
Energy 53ENERGY BALANCE Energy balance is achieved when the energy provided by the food and the energy expended by the body is nearly equal. This will enable the individuals to maintain ideal body weight. When the body has excess energy in the form of extra calories, the extra calories are converted into fat and stored in the adipose tissues. When individuals lead a sedentary lifestyle and their energy intake consistently exceeds their energy expenditure, it results in gradual weight gain. The person will be overweight and over a period of time, it will lead to obesity. When an individual does not get enough calories and the body weight is less than 10% of the reference weight, it leads to underweight.OBESITY Obesity is the deposition of excessive fat around the body, particularly in the subcutaneous tissue. It can be measured by calculating the weight/height ratio and by the body mass index (BMI).Causes of ObesityMany factors influence the development of obesity. Inappropriate eating due to work routine, unable to access or ignorance about healthy foods. Overeating may be due to psychological stress, anxiety, depression and loneliness. Food alleviates these emotions temporarily as food is seen as a comfort. Slow metabolic rate may be inherited. Obesity runs in families. If both parents are obese, the child has an 80% chance of being obese. If one parent is obese, the child has a 40% chance of being obese. Behavioural and poor eating habits also play a role in the occurrence of obesity. Eating certain calorie- dense foods over a period of time with no or very little physical activity makes a person gain weight.Body Mass Index (BMI)BMI is the body weight in kilograms divided by the square of height in metres (kg/m2). It correlates with body fatness and health risks associated with obesity. Obesity refers to the degree of fatness or the relativeexcess amount of fat in the total body composition. Weight in kilograms BMI = (Height in metres)2 = 58 kg/(162 cm)2 = 58/(1.62)2 = 58/2.62 = 22.1 If BMI = 20–25, mortality is least. ≥ 25 = overweight ≥ 30 = obese
Nutrition and Biochemistry for Nurses54 OBESITY GUIDELINES FOR I NDIA—F ORMULATED BY ThE hEALT h MINISTRY OF INDIA Bearing in mind a greater risk of obesity and metabolic syndrome among Indians, Ministry of Health has formulated a set of guidelines for Indians to prevent the rising epidemic of Type II diabetes and metabolic syndrome. Overweight, if the BMI is 23 kg/m2 or more. The international standard is 25 kg/m2. Obese, if the BMI is 25 kg/m2 or more. The international standard is 30 kg/m2. An Indian needs drug therapy for obesity if the BMI is 25 kg/m2. An Indian qualifies for bariatric surgery for obesity if the BMI is 32.5 kg/m2 as compared to 35 kg/m2 for international patients. Benefits of the new guidelines Absolute mortality due to chronic heart disease in India will increase. To prevent such deaths, these guidelines are formu- lated. The number of persons with diabetes in India is expected to increase by 170% in the next 20 years. These guidelines are for the substantial prevention of these diseases. Chapter in a Nutshell Energy is the ability to do work. Body requires energy not only to do work but also during rest. The energy required for basal metabolism like breathing, metabolism and regulation of body temperature is called resting energy expenditure. Energy is released by the metabolism of food and is utilized by the body to maintain life. The unit of energy is calorie. The energy requirement of an individual depends on his basal metabolic rate (BMR), physical activity and thermic effect of food. BMR is the minimum amount of energy required by a person; several factors like hormones, exercise and gender affect the BMR. Thermic effect of food is generally calculated as 10%. The amount of energy present in food is measured by calorimetry. Energy requirement of an individual is calculated using his age, sex, physical activity and weight. Energy balance is achieved when the energy provided by the food and the energy expended is nearly equal. Obesity is the deposition of excessive fat in the body and can be calculated by using the body mass index (BMI).
Energy 55 ExercisesLong Answer Question 1. Define total energy requirement and explain in detail the factors determining it.Short Answer Question 1. Write short notes on the following: a. Bomb calorimeter b. BMI and BMR c. Points to consider for calculating BMR in an individual d. Factors affecting energy requirementMultiple Choice Questions 1. Energy required in addition to total calories for a lactating mother from 0–6 months is (a) +350 kcal (b) +450 kcal (c) +550 kcal (d) +600 kcal 2. Basal metabolic rate is measured in (a) Postabsorptive state (b) Lying down (c) Awake (d) All of the above 3. Obesity is usually assessed by (a) BMI (b) BMR (c) Growth chart (d) None of the above 4. BMR is affected by (a) Body temperature (b) Body size (c) Gender (d) All of the above 5. Food energy is measured in (a) Kilocalories (b) Proteins (c) Grams (d) None of the aboveFill in the Blanks 1. Energy present in foods is usually expressed as ________. 2. Energy ________ will help individuals maintain ideal weight. 3. BMR is expressed as ________. 4. ________ is the deposition of excess fat in the body. 5. ________ are an example of sedentary physical activity.
Nutrition and Biochemistry for Nurses56 True or False 1. Benedicts’s oxycalorimeter uses indirect calorimetry to measure the amount of energy present in foods. ( ) 2. Mortality is least when BMI is 20‒25. ( ) 3. Work done by students is considered as heavy physical activity. ( ) 4. Sleep increases BMR by 10%. ( ) 5. Thermogenic or thermic effect of food is always calculated as 15%. ( ) ANSWERS Multiple Choice Questions 1. (d), 2. (d), 3. (a), 4. (d), 5. (a). Fill in the Blanks 1. kilocalories, 2. expenditure, 3. kcal/m²/h, 4. Obesity. 5. Desk jobs. True or False 1. True, 2. True, 3. False, 4. True, 5. False.