Energy balance (the difference between energy consumption and energy expenditure) should always be considered a corner stone of nutritional planning. Energy balance dictates many metabolic processes which influence nutrient needs. Considering this ensuring an appropriate energy intake relative to expenditure will ensure nutritional recommendations are correct.
Components of energy balance
Expenditure –
There are a myriad of factors that alter an individuals Total Energy Expenditure (TEE) or how much total energy an individual burns each day. Below is a breakdown of the components of energy expenditure.
BMR/RMR (Basal/Resting Metabolic Rate)
Basal metabolic rate is the amount of energy an individual needs to survive when the individual is at total rest (no movement, no stimulation and no influences from food or any other substances). This is basically the amount of energy that’s needed for basic bodily functions such as breathing, and normal cellular turnover.
BMR is body weight dependent (obviously there is more tissue to support). However in terms of BMR fat is reasonably inactive metabolically (although not totally), this is why a greater muscle mass will increase an individuals metabolic rate.
To determine your BMR it’s possible to use the Schofield equation presented in fig 6.1
Fig 6.1
Note: W is weight in kilograms.
During energy restriction a change in hormones can effect BMR (i.e. T2 out put etc)
PAL (Physical activity level)
To perform an activity requires energy, so the more active you are the higher your energy expenditure will be. Differing activities require differing energy expenditures to complete and it’s possible to work out in detail all the activities in a day and multiple your BMR by the corresponding PAR (physical activity ratio – how many times above resting energy values the activity takes to complete). For simplicity sake it’s easier to use an average based on how active you are at work and during your leisure (non occupational) time. Figure 6.2 gives these estimates based on work, gender and leisure time. In relation to occupational activity, light is considered office based work; moderate is shop floor type activities and light labour whilst heavy would constitute hard physical labour.
To calculate an estimate of TEE you would just multiple your BMR by the PAL (Physical Activity Level) that’s determined by your occupational and non occupational activities.
Fig 6.2
It has to remember that these calculated levels are estimates and should only be used as such. It becomes obvious that exercise although a great energy burning activity will only constitute one to two hours of activity in a twenty four hour period and as such non exercise activities can aid greatly in raising or lowering ones energy expenditure when trying to increase or decrease body weight or alter body composition.
The second factor relating to energy expenditure and physical activity is the influence of certain activities upon resting metabolic rate after the activity has been completed. It has been shown that a person’s metabolism can be elevated after exercise for any were up to twenty four to forty eight hours. It appears this elevation in metabolism is dose responsive with higher intensities linearly increasing the amount and duration that the metabolism is increased by.
It is thought that the increase in metabolism is a natural response in order for greater tissue turnover and substrate repletion to occur which obviously requires energy.
DIT (Dietary Induced Thermogenosis)
When food is eaten and digested and metabolized it requires a certain amount of energy to do this. This expenditure of energy to process the energy from food is called Dietary induced thermogenosis (DIT) or the Thermic Effect of Feeding (TEF).
The thermic effect of feeding is not a constant as it varies with certain factors such as differing macronutrient composition and possibly the amount of feeds within a day. Typically the thermic effect of food is estimated at ten percent of total energy, although this varies from around five to fifteen percent for a mixed meal. the composition of the meal determines the thermic effect as different macronutrients have different thermogenic qualities. Fat appears to have the least thermic effect with an increase of 0-3% for lipids ingested, carbohydrates are 5-10% and proteins 20-30% of energy ingested (Tappy 1996)
NEAT (Non Essential Activity Thermogenosis)
Some individuals appear to have a higher metabolic rate than others even though they can be similar in build and activity levels. Some believe the differences are due to non essential activities, in other words small bodily movements that are hard to account for such as foot tapping, fidgeting etc.
It is believed that reducing these movements is one of the first ways the body compensates against reduction of dietary energy in order to maintain body weight. Considering this it has been suggested that you can artificially raise or maintain NEAT by performing activities such as chewing gum, squeezing small rubber balls with your hands, performing finger extensions against elastic bands etc during your normal everyday activities.
Some individuals who are termed spendrift phenotypes appear to raise their levels of NEAT in response to overfeeding and would typically not gain as much weight as individuals who don’t who are termed thrifty phenotypes.
Adaptive Thermogenosis
This is energy expended that cannot be accounted for under the above categories, some people include NEAT within this category for simplicity sake. Adaptive thermogenosis also includes energy expended due to emotional and environmental factors such as anxiety, cold and various other stimulatory factors.
Energy consumption
Energy is obtained via four possible sources, either carbohydrates, fat, protein or alcohol. The amount of energy per gram for each nutrient differs and is termed the atwater facors. Typically fat is the most energy dense of the macronutrients withit providing nine calories per gram.After this alcohol presents the next energy dense substrate with seven calories per gram. Finally carbohydrates both provide roughly four calories per gram.
Energy Flux - why a calorie isn’t a calorie
Energy balance is governed by the law of thermodynamics in that a reduction or increase in energy must result in either use of stored energy or storage of the excess energy, however energy balance isn’t a fixed entity in that as one variable changes on either side of the equation it can effect a factor from the other side. This will mean that even though there will be a decrease or increase in weight the composition of the diet will determine where the increase or decrease will come from - I.e. muscle or fat or whether a continued shift in energy balance will occur as energy expenditure will be mediated. For example if there is a large decrease in energy consumption several factors will change both in the short term and long term in order to bring down energy expenditure, for example muscle losses will mean a decrease in BMR, the body will down regulate thermogenic hormones, the body will attempt to decrease NEAT and other physical activities all in order to try to prevent further weight loss.
Not only energy consumption has this effect as it has been shown that different fatty acids have different effects on fat oxidation with oleic acid having different effects from the saturated fatty acid palmitic acid. The total energy from the two will be the same, but the consequential effect on long term metabolise will be different and therefore effect energy balance at a later point. Other factors are issues such as satiety and its effect on later energy consumption with an example being an individual was to take in two hundred calories in the form of table sugar compared to two hundred calories consumed from apples with the apples having a more pronounced effect on satiety and the total amount of energy consumed at the next meal.
The bottom line is that in the short term energy balance is the most important factor but for optimal and continued changes in body composition the composition of the diet is equally important.
Components of energy balance
Expenditure –
There are a myriad of factors that alter an individuals Total Energy Expenditure (TEE) or how much total energy an individual burns each day. Below is a breakdown of the components of energy expenditure.
BMR/RMR (Basal/Resting Metabolic Rate)
Basal metabolic rate is the amount of energy an individual needs to survive when the individual is at total rest (no movement, no stimulation and no influences from food or any other substances). This is basically the amount of energy that’s needed for basic bodily functions such as breathing, and normal cellular turnover.
BMR is body weight dependent (obviously there is more tissue to support). However in terms of BMR fat is reasonably inactive metabolically (although not totally), this is why a greater muscle mass will increase an individuals metabolic rate.
To determine your BMR it’s possible to use the Schofield equation presented in fig 6.1
Fig 6.1
Gender |
Age group |
Calculation for BMR (kcal/d) |
Male |
10-17 |
(17.7 xW)+657 |
|
18-29 |
(15.1 xW)+692 |
|
30-59 |
(11.5 xW)+873 |
Female |
10-17 |
(13.4 xW)+692 |
|
18-29 |
(14.8 xW)+487 |
|
30-59 |
(8.3 xW)+846 |
Note: W is weight in kilograms.
During energy restriction a change in hormones can effect BMR (i.e. T2 out put etc)
PAL (Physical activity level)
To perform an activity requires energy, so the more active you are the higher your energy expenditure will be. Differing activities require differing energy expenditures to complete and it’s possible to work out in detail all the activities in a day and multiple your BMR by the corresponding PAR (physical activity ratio – how many times above resting energy values the activity takes to complete). For simplicity sake it’s easier to use an average based on how active you are at work and during your leisure (non occupational) time. Figure 6.2 gives these estimates based on work, gender and leisure time. In relation to occupational activity, light is considered office based work; moderate is shop floor type activities and light labour whilst heavy would constitute hard physical labour.
Non occupational activity |
Occupational work |
|
|
|
|
|
|
Males |
|
|
Females |
|
|
|
light |
moderate |
heavy |
light |
moderate |
heavy |
Non active |
1.4 |
1.6 |
1.7 |
1.4 |
1.5 |
1.6 |
Moderately active |
1.5 |
1.7 |
1.8 |
1.5 |
1.6 |
1.7 |
Very active |
1.6 |
1.8 |
1.9+ |
1.6 |
1.7 |
1.8+ |
To calculate an estimate of TEE you would just multiple your BMR by the PAL (Physical Activity Level) that’s determined by your occupational and non occupational activities.
Fig 6.2
It has to remember that these calculated levels are estimates and should only be used as such. It becomes obvious that exercise although a great energy burning activity will only constitute one to two hours of activity in a twenty four hour period and as such non exercise activities can aid greatly in raising or lowering ones energy expenditure when trying to increase or decrease body weight or alter body composition.
The second factor relating to energy expenditure and physical activity is the influence of certain activities upon resting metabolic rate after the activity has been completed. It has been shown that a person’s metabolism can be elevated after exercise for any were up to twenty four to forty eight hours. It appears this elevation in metabolism is dose responsive with higher intensities linearly increasing the amount and duration that the metabolism is increased by.
It is thought that the increase in metabolism is a natural response in order for greater tissue turnover and substrate repletion to occur which obviously requires energy.
DIT (Dietary Induced Thermogenosis)
When food is eaten and digested and metabolized it requires a certain amount of energy to do this. This expenditure of energy to process the energy from food is called Dietary induced thermogenosis (DIT) or the Thermic Effect of Feeding (TEF).
The thermic effect of feeding is not a constant as it varies with certain factors such as differing macronutrient composition and possibly the amount of feeds within a day. Typically the thermic effect of food is estimated at ten percent of total energy, although this varies from around five to fifteen percent for a mixed meal. the composition of the meal determines the thermic effect as different macronutrients have different thermogenic qualities. Fat appears to have the least thermic effect with an increase of 0-3% for lipids ingested, carbohydrates are 5-10% and proteins 20-30% of energy ingested (Tappy 1996)
NEAT (Non Essential Activity Thermogenosis)
Some individuals appear to have a higher metabolic rate than others even though they can be similar in build and activity levels. Some believe the differences are due to non essential activities, in other words small bodily movements that are hard to account for such as foot tapping, fidgeting etc.
It is believed that reducing these movements is one of the first ways the body compensates against reduction of dietary energy in order to maintain body weight. Considering this it has been suggested that you can artificially raise or maintain NEAT by performing activities such as chewing gum, squeezing small rubber balls with your hands, performing finger extensions against elastic bands etc during your normal everyday activities.
Some individuals who are termed spendrift phenotypes appear to raise their levels of NEAT in response to overfeeding and would typically not gain as much weight as individuals who don’t who are termed thrifty phenotypes.
Adaptive Thermogenosis
This is energy expended that cannot be accounted for under the above categories, some people include NEAT within this category for simplicity sake. Adaptive thermogenosis also includes energy expended due to emotional and environmental factors such as anxiety, cold and various other stimulatory factors.
Energy consumption
Energy is obtained via four possible sources, either carbohydrates, fat, protein or alcohol. The amount of energy per gram for each nutrient differs and is termed the atwater facors. Typically fat is the most energy dense of the macronutrients withit providing nine calories per gram.After this alcohol presents the next energy dense substrate with seven calories per gram. Finally carbohydrates both provide roughly four calories per gram.
Energy Flux - why a calorie isn’t a calorie
Energy balance is governed by the law of thermodynamics in that a reduction or increase in energy must result in either use of stored energy or storage of the excess energy, however energy balance isn’t a fixed entity in that as one variable changes on either side of the equation it can effect a factor from the other side. This will mean that even though there will be a decrease or increase in weight the composition of the diet will determine where the increase or decrease will come from - I.e. muscle or fat or whether a continued shift in energy balance will occur as energy expenditure will be mediated. For example if there is a large decrease in energy consumption several factors will change both in the short term and long term in order to bring down energy expenditure, for example muscle losses will mean a decrease in BMR, the body will down regulate thermogenic hormones, the body will attempt to decrease NEAT and other physical activities all in order to try to prevent further weight loss.
Not only energy consumption has this effect as it has been shown that different fatty acids have different effects on fat oxidation with oleic acid having different effects from the saturated fatty acid palmitic acid. The total energy from the two will be the same, but the consequential effect on long term metabolise will be different and therefore effect energy balance at a later point. Other factors are issues such as satiety and its effect on later energy consumption with an example being an individual was to take in two hundred calories in the form of table sugar compared to two hundred calories consumed from apples with the apples having a more pronounced effect on satiety and the total amount of energy consumed at the next meal.
The bottom line is that in the short term energy balance is the most important factor but for optimal and continued changes in body composition the composition of the diet is equally important.
