Principles of Human Nutrition - Assignment Example

Principles of Human Nutrition Using the FAO/WHO/UNU (1985) equations calculate the BMR (kJ/day) of: a) A 26 year old woman weighing 62 kg b) A 26 year old man weighing 76 kg The Schofield equation or FAO/WHO/UNU (1985) equation is used to predict the basal metabolic rate (BMR) in kcal/day. The BMR is the rate at which the body expends energy on maintenance activities such as heart beat, cellular processes, moving of respiratory muscles. The BMR is affected by e.g. gender, climate, body weight, body composition, genetics. The equation varies according to gender, age and body weight. Thus, after selecting the correct age-bracket and gender, an equation is given with the body weight as variable. Then the body weight is entered into the equation (in kg), which finally allows the calculation of the BMR in kcal/day. Since the question asks for the BMR in kJ/day, this has been converted by multiplying the BMR value with 4.184 (1 kcal = 4.184 kJ). 1a) Schofield equation for an 18 – 30 year old female: BMR = 14.7 x weight (kg) + 496 in kcal/day BMR calculation for a 26 year old female weighing 62 kg: BMR = 14.7 x 62 + 496 = 1407.4 kcal/day Conversion of the value from kcal/day into kJ/day: BMR = 1407.4 x 4.184 kJ/day = 5888.6 kJ/day 1b) Schofield equation for an 18 – 30 year old male: BMR = 15.3 x weight (kg) + 679 in kcal/day BMR calculation for a 26 year old male weighing 76 kg: BMR = 15.3 x 76 + 679 = 1841.8 kcal/day Conversion of the value from kcal/day into kJ/day: BMR = 1841.8 x 4.184 kJ/day = 7706.1 kJ/day Therefore, a 26 year old woman weighing 62 kg has a BMR of 5889 kJ/day and a 26 year old man weighing 76 kg has a BMR of 7706 kJ/day. 2) Using the FAO/WHO/UNU (1985) equations calculate the BMR (kcal/day) of: a) A one year old girl weighing 10 kg. b) A three year old boy weighing 16 kg The calculation is been carried out in a similar fashion as in question 1. The Schofield equation also gives age-brackets for children considering the special energy requirements for growing bodies. 2a) Schofield equation for a 0 - 3 year old girl: BMR = 61 x weight (kg) - 51 in kcal/day BMR calculation for 1 year old girl weighing 10 kg: BMR = 61 x 10 - 51 = 559 kcal/day 2b) Schofield equation for a 3 - 10 year old boy: BMR = 22.7 x weight (kg) + 495 in kcal/day BMR calculation for a 3 year old boy weighing 16 kg: BMR = 22.7 x 16 + 495 = 858.2 kcal/day Therefore, a one year old girl weighing 10 kg has a BMR of 559 kcal/day and a three year old boy weighing 16 kg has a BMR of 858 kcal/day. 3) Calculate the daily energy requirements (kcal/day) of a woman aged 32 years, weighting 66 kg and who works as a nurse. The daily energy requirements of a person combine the energy requirements for regular maintenance activities of the body (as measured with the BMR) with any other activities, especially physical activities. It is largely influenced by the basal metabolic rate, but also on physical activity, dietary induced thermogenesis (DIT) and on growth. The daily energy requirements can be predicted by multiplying the basal metabolic rate with an activity factor according to the magnitude of physical activity undertaken throughout the day. The factors also vary depending on the gender. Therefore, the BMR is initially calculated as described above. The resulting value is then multiplied by the activity factor to give the daily energy requirement. Schofield equation for a 30 – 60 year old female: BMR = 11.6 x weight (kg) + 879 in kcal/day BMR calculation for a 32 year old female weighing 66 kg: BMR = 11.6 x 66 + 879 = 1644.6 kcal/day Daily energy requirement of a woman aged 32 years, weighing 66 kg and who works as a nurse: Nurse: moderate activity, activity factor 1.6 EE = BMR x activity factor = 1644.6 kcal/day x 1.6 = 2631.4 kcal/day Therefore, a woman aged 32 years, weighing 66 kg has a daily energy requirement of 2631 kcal/day. 4) What are the minimum energy requirements (kJ/day) for survival for the subject listed in question 1 b. The basal metabolic rate (BMR) gives the rate at which the body expends energy only on maintenance activities and general life-sustaining activities such as heart beat and respiration. In this sense the BMR gives the minimum energy requirement for survival e.g. without any physical activity. A 26-year-old man weighing 76 kg (subject listed in question 1b) has therefore a minimum energy requirement of 7706 kJ/day, if he does not engage in any other (e.g. physical) activities. In situations of fasting or starving, the body will use energy reserves of the body, initially glycogen and body fat, then proteins as source of energy. This can only be sustained for a limited time. 5) Determine how many grams of rice will be required to feed 200 male army new recruits at Sandhurst for 3 days (for simplicities sake assume they don’t eat anything other than rice)! The Schofield equation cannot be applied without the knowledge of the weight and age of an individual. The gender is given in the question, but one has to estimate age and body weight of the recruits. First the energy requirement per day will be calculated for one recruit with use of estimated average values of age and body weight. Then this value will be scaled up to 200 men for 3 days. And finally this energy requirement will be converted into the required amount of rice. One can estimate an average of 75 kg body weight per man. Furthermore, all recruits will be within the age bracket of 18 – 30 years old. Rice consists mainly of carbohydrates, therefore, one can assume that 1 gram of rice contains 4 kcal in stored energy. Schofield equation for an 18 – 30 year male: BMR = 17.5 x weight (kg) + 651 in kcal/day BMR calculation for an average male recruit weighing 75 kg: BMR = 17.5 x 75 + 651 = 1963.5 kcal/day Now the activity factor has to be included for the calculation of the daily energy requirement. The daily energy requirement of a recruit aged between 18 and 30 years, weighing 75 kg: Recruit: heavy activity, activity factor 2.1 EE = BMR x activity factor = 1963.5 kcal/day x 2.1 = 4123.4 kcal/day So far this has been calculated for a single recruit for one day. 200 recruits need for 3 days: EE = 4124.4 kcal/day x 3 days x 200 = 2,474,000 kcal Rice is mainly composed of carbohydrates and it has an energy content of 4 kcal/g. For 200 recruits for 3 days, one needs: (2,474,000 kcal) / (4 kcal/g) = 618,500 g = 618.5 kg rice Therefore, 200 recruits need 618,500 g rice for three days, if one assumes that the recruits only eat rice and weigh 75 kg in average. This value would be ca. 13 % lower, if one assumes an average body weight of 60 kg, and it would be ca. 13 % larger, if one assumes an average body weight of 90 kg (calculation using the same equation as above). 6) The Department of Health recommends that a balanced diet include more than 50% its energy from carbohydrate. In kilograms, what is the minimum amount of carbohydrate per day a male aged 26 years and weighing 82 kg who works in an office consume? Schofield equation for an 18 – 30 year old male: BMR = 17.5 x weight (kg) + 651 in kcal/day BMR calculation for a 26 year old male weighing 82 kg: BMR = 17.5 x 82 + 651 = 2086.0 kcal/day Daily energy requirement of a male aged 26 years, weighing 82 kg who works in an office: Work in office: light activity, activity factor 1.6 EE = BMR x activity factor = 2086.0 kcal/day x 1.6 = 3337.6 kcal/day Minimum energy requirement coming from carbohydrates: 0.5 x EE = 1668.8 kcal/day Carbohydrates contain 4 kcal per gram. Minimum amount of carbohydrates per day for a male aged 26 years, weighing 82 kg and working in an office: (1668.8 kcal/day) / (4 kcal/g) = 417.2 g carbohydrates/day = 0.4172 kg carbohydrates/day Therefore, 26 year old male weighing 82 kg and working in an office needs a minimum of 0.417 kg carbohydrates per day. 7) What is the main advantage of using an equation to predict BMR? The main advantage of using an equation to predict the BMR is the fact that the equation simplifies a rather complex situation. The basic information gender, age and body weight is usually available. Therefore it is possible to study large groups with a standardized scheme. The simplification using an equation allows epidemiological studies on basal metabolic rate and daily energy requirements. Furthermore a doctor (or nurse) can quickly assess the BMR of a patient. When also considering the activity level of a patient, the doctor can then calculate the daily energy requirement. Therefore it allows to quickly estimating whether an individual has a calorie intake above or below his/her daily energy requirement. Individuals can even self-assess themselves in order to control energy intake while maintaining a balanced diet. This is especially important with the increasing number of overweight and obese people, who have to control their energy intake in order to loose weight. 8) What is the main disadvantage of using an equation to predict BMR? The simplicity of the Schofield equation is also its main disadvantage. It is in fact a rather crude way to estimate the BMR. As already pointed out, there are several factors affecting the BMR besides gender, age and body weight. These are e.g. genetics, climate, body composition, hormone levels, pharmacological agents and emotions. When considering body composition it seems obvious that a very fit and muscular person will not have the same BMR compared to a person of the same age weight and gender, but with fat tissue instead of muscles. The same can be considered for two people of the same gender, age and body weight, who live in different climates. In a cold climate, the body needs to convert more energy into heat in order to maintain a constant body temperature. Hence, the person’s BMR can be expected to be higher. This means that the Schofield equation cannot give a detailed answer how a person’s calorie intake relates to the BMR and the daily energy requirement. Thus the Schofield equation does not consider any other circumstances of a person and this increases the potential error when using the equation. However, it can serve as a rough guide when no further information is available. 9) Find a journal article about basal metabolic rate and then write one sentence using that reference in the correct context. In a recent study, the BMR of Australian men and women has been measured. The found values have been compared to the predicted data, calculated with the Schofield equation (Piers et al 333). 10) Give the full details of the reference you used in question 9 (as you would put in a reference list at the end of your report). Piers, LS; Diffey, B; Soares, MJ; Frandsen, SM; McCormack, LM; Lutschini, MJ; Odea, K. “The validity of predicting the basal metabolic rate of young Australian men and women.” European Journal of Clinical Nutrition 51 (1997): 333-337. Read More