The measure of energy Flashcards
calculating energy requirements
the body will consume about 25 kcals per kg of body weight per day
25 x BW = BMR
eg 70kg person would have a BMR of 1750 (25x70)
highly unlikely someone will remain sedentary over 24 hour period
if said person had a sedentary lifestyle an additional 20% would need to be added onto BMR
if said person was moderately active an additional 50% would need to be added to BMR
if said person was very active, an additional 100% would need to be added on
E.g. 1750 x 0.5 (50%) = 875
875 + 1750 = 2625 kcals (RMR)
The Schofield Equation
takes into account gender. Also has SEE (standard error of estimation ~ can use this number to add or minus to BMR depending on person’s actual energy requirement).
males:
10-17 years ~ BMR = 17.7 x BW + 657 (SEE = 105)
18-29 years ~ BMR = 15.1 x BW + 692 (SEE = 156)
30-59 years ~ BMR = 11.5 X BW + 873 (SEE = 167)
females:
10-17 years ~ BMR = 13.4 X BW + 692 (SEE = 112)
18-29 years ~ BMR = 14.8 X BW + 487 (SEE = 120)
30-59 years ~ BMR = 8.3 X BW + 846 (SEE = 112)
activity level ~ males ~ females:
sedentary ~ BMR X 1.4 ~ BMR X 1.4
moderately active ~ BMR X 1.7 ~ BMR X 1.6
very active ~ BMR X 1.9 ~ BMR X 1.8
extremely active ~ BMR 2.4 ~ BMR X 2.2
calculating nutrient requirements (carbs, fats, protein)
carbs = 60% of total energy eg. 3069 x 0.60 (60%) = 1841 1841 / 4 (kcal per gram) = 460g fat = 25% of total energy eg. 3069 x 0.25 = 767 767 / 9 (kcal per gram) = 85g protein = 15% of total energy eg. 3069 x 0.15 = 460 460 / 4 (kcal per gram) = 115g
fat storage/mass
if a person weighing 60kg had 20% body fat, their actual fat mass (FM) would be:
60 x 0.2 = 12kg
carbs storage
(glycogen storage)
fluctuates depending on body size and muscularity
body stores about 6.25g of glycogen per kg of bodyweight - those following high carb diet can increase this capacity.
an 80kg person would therefore store glycogen in following manner:
liver glycogen 100g = 400 kcal
muscle glycogen 400g = 1600 kcal
blood plasma glucose 3g = 12 kcal
protein storage
no reference to the energy value of protein storage is made in this section because:
- the use of protein as a source of energy is an undesirable outcome that would only occur when glycogen stores are depleted
- its not possible to accurately calculate how much muscle or protein tissue is actually stored within the body because fat free mass includes many other variables including bone mass, water, minerals, connective tissues, none of which have energy value.
metabolism
- term used to describe the sum of all energy-related reactions in the body
- directly related to body temperature
- all metabolic processes ultimately result in heat production - so metabolic rate and body temp are considered to be the same
- during exercise or physical activity, energy expenditure increases; this results in a greater production of heat = raises body temperature
- shivering is an involuntary muscle contraction used to increase energy expenditure and raise body temperatures in cold environments
energy
- defined as ‘the ability or capacity to perform work’
- cannot be created or destroyed, but transforms from one state to another without being depleted
- generally measured using kilogram calories (1000 calories) which are usually referred to as kcals
- to convert kcal to kj use 1kcal = 4.186 kj
chemical energy
- stored in foods we consume
- not immediately metabolised to fuel work by the body
- stored for use at a later time
- when this stored energy is required during exercise, it is metabolised to created mechanical energy within skeletal muscles
- this energy changes again into heat energy, which is then released or dissipated from the cells
kilocalorie
defined as the volume of energy and heat required to raise the temperature of 1 litre of water (1 kg) by 1 degrees
catabolic reactions
those that require the breakdown of larger molecules into smaller ones
- the breakdown of carbs into glucose, proteins into amino acids
anabolic reactions
- those that require the synthesis of larger molecules from smaller ones
- e.g. the combination of amino acids to form skeletal muscle and combination of fatty acids to create adipose fatty tissue
- hypertrophy of skeletal muscles after resistance training is one of most commonly discussed anabolic reactions
metabolic rate
- describes the quantity of energy required by the body to perform all its biological processes during a specific period of time
- mostly used to describe the quantity of energy needed each day to sustain all metabolic reactions
- it is affected by and comprises of 3 components = basal metabolic rate, thermic effect of feeding, physical activity
basal metabolic rate (BMR)
- describes the minimum amount of energy required by the body to sustain life
- it is the quantity of energy needed to keep you alive if you were to remain completely inactive and refrained from eating for a 24 hour period
- largely influenced by age, body mass and body composition ~ higher levels of lean muscle tissue will require more energy
the thermic effect of feeding
(TEF)
- describes total energy required to fuel all digestive and absorption processes
- TEF represents approx 10% of the body’s total energy expenditure - but this is also influenced by types of foods consumed and their micro and macro content
- whilst TEF stimulates an increase in energy expenditure, a lack of feeding has the opposite effect ~ this is why starvation and fasting are not the best techniques for weight loss because they do not increase energy expenditure ~ instead they reduce metabolism and make it harder to expand energy in the long term
