energy intake and expenditure

Question 1

general principles of energy expenditure
- calculation of what happens to energy produced and what each means
- what 3 things make up energy expenditure
- calculation for energy expenditure
- how to increase and decrease metabolism

Answer 1

-sum of energy = heat + work
energy released from breakdown of chemical bonds in organic molecules is either released as heat (75-80%) or used to perform work (20-25%)
- basal metabolic rate (BMR)- energy expended at rest (around 65%)
- thermic effect of food (TEF)- energy required to digest and absorb food (around 10%)
- energy expended during physical activity (around 25%, but varies depending on individual, intensity, etc.)
- EE = BMR x physical activity level
- increase- growth, pregnancy, menstruation, when ill, body temp high, eating, activity, stress
- decrease- sleep, ageing, gender, fasting

Question 2

how to measure it
- oxygen consumption- VO2 (and why)
- metabolic equivalent of task- MET
- calories- kcal
- kilojoules
- link the last 2

Answer 2

• volume of o2 used by body to convert energy from food to work/heat. all energy releasing reactions depend on o2 (ATP replacement) so vo2 is an accurate indirect measurement of energy expenditure.
• multiples of resting metabolic rate, so 1 MET is energy expenditure when sitting quietly (3.5 ml02 / kg of body weight / min)
• 1 kcal is quantity of heat needed to raise temp of 1L of water by 1 deg
• is the standard unit of food energy. 1J is replaced in 1 sec by average person at rest
• kcal->KJ = multiply kcal by 4.184, therefore 0.004184 kcal released in 1 sec by average person at rest

Question 3

energy intake
- what is it
- most to least energy dense macronutrients
- average person uses of kcal and how it impacts intake
- average recommendations of kcal intake

Answer 3

• energy obtained by food and drink (macronutrients) by oxidation of carbs, fat, protein, alcohol
• fat, alcohol, protein, carbs
• average kcal use between 1500-3500 dependent on BMR and activity levels, so intake levels different for everyone
• men 2500 kcal, women 2000 kcal