We need energy to move, grow, breakdown & absorb nutrients & carry out essential bodily processes for sustenance of our life. The total amount of energy we use for these processes daily is referred to as total energy expenditure(TEE). It is divided into the following:
- Resting Energy Expenditure(REE) or Basal Metabolic Rate(BMR): This refers to energy used at rest to carry out basic life sustaining functions such as blood circulation, metabolic functions & breathing(to name a few). REE accounts for 70% to 80% of total daily energy expenditure.
- Activity induced activity expenditure: This refers to the amount of energy spent on physical activity including purposeful activity such as exercise, workout & non purpose activity such as fidgeting. This accounts for 15% to 20% of total energy expenditure
- Diet induced activity expenditure: This refers to energy spent on digesting & absorbing food. This accounts for 10% of total energy expenditure.
We have discussed this in detail in our earlier blog.
To summarise, total energy expenditure is equal to = Basal Metabolic Rate( 75%)+Activity induced expenditure(15%)+ Diet induced expenditure(10%).
This essentially means for weight loss higher BMR is beneficial & as such your gut health would play a major role in achieving your weight loss goals.
In order to expend energy on growth, movement & various metabolic functions, we need to first consume energy. We do this by consuming food that contains chemical energy( calories). The total number of calories we consume in a day is referred to as energy intake. The difference between calorie intake & calorie expenditure is called either calorie surplus or calorie deficit.
In other words, Energy balance( calorie surplus/deficit)=Total energy intake- energy expenditure.
We have perfect energy balance when total energy intake=energy expenditure. Simply put, when we go for a run, we convert our chemical energy ( coming from food we eat) to kinetic energy as we move & a part gets lost as heat energy. However, the overall energy system remains intact.
We can also say that energy balance~ energy intake=Basal Metabolic Rate +Activity induced expenditure + Diet induced expenditure
Weight gain happens from calorie surplus( calorie intake> calorie expenditure) & this has lot of do with your BMR( which is influenced by your gut health, a leaky gut results in food getting stored in the body for a longer period of time rather than getting processed & used & residual waste being flushed through our digestive tract)
It is important to note that energy intake or chemical energy can either be converted into kinetic energy( through activity induced energy expenditure) or stored in the form of triglycerides, glycogen, proteins, bones, new tissues & cells. When we are in energy surplus, we end up gaining weight & most of it is in the form of fat. Similarly, we create an energy deficit when energy expenditure is more than energy intake. So the question arises when we consume less, how can we expend more? You do so by resorting to energy stores in your body. You end up breaking down triglycerides stored into fatty acids which is then burned through fat oxidation to release energy. As a result, we end up losing weight & burn fat.
We have discussed in our earlier blog about the factors that impact our RMR or REE. So I am not going to discuss them here. However, I am going to discuss the genetic impact on our BMR.
Your genetic makeup has a considerable influence on your BMR. 40% of variation in your BMR is due to genetic differences/makeup. Variants of UCP2 gene contributes to your these genetic differences.
For calculating RMR, mathematical formulas are most popular. You can access such calorie calculators on the internet, app or wearable devices. The Harris & Benedict equation created in 1918 & amended in 1984 remains the most prominent way of calculating RMR. Although this H&B equation is used to calculate Basal Metabolic rate, it is used interchangeably. We have shared the revised & updated H&B equations for males & females in our book. We are again mentioning the equations here:
- Men: 88.362 + (13.397 × weight in kg) + (4.799 × height in cm) – (5.677 × age in years)
- Women: 447.593 + (9.247 × weight in kg) + (3.098 × height in cm) – (4.330 × age in years)
For instance, a 40 year old male, with 75 kg weight & 180 CM height would require 1729 calories to carry our normal physiological functions.These formulas have some potential errors since it assumes that human beings with the same gender, age, height & weight would have the same RMR which is not correct. Your lean body mass significantly influences RMR & should be considered.
Although Katch-McArdle and Cunningham formulas are derived from lean body mass rather than total body, they rely on accurate measurement of lean body mass.
Katch-McArdle formula(BMR): 370+(21.6*Lean body mass)
Cunningham formula(RMR): 500+ (22* Lean body mass)
Lean body mass= total body weight *(100-body fat %)
Although new equations continue to emerge, each one would have varying degrees of errors.
Our BMR makes up for the majority of energy expenditure & a higher BMR means higher total energy expenditure. Our Gut health plays an important role in maintaining a high since a healthy gut improves our digestion process & metabolic processes & does not lead to storing foods in our body.
It was found that people having issues with their gut health tend to have low gut microdiversity & high BMI. This translates into positive energy balance & weight gain. Christensenella is an important gut bacteria also helps in weight control.
It is important to remember that your gut will play an important role in improving your BMR. However, most of us consider activity induced expenditure viable for weight loss vis-a-vis increasing BMR. A long term perspective for having a healthy weight is to improve your BMR by having a healthy gut. Please remember that if you focus on weight loss through activity induced energy expenditure, your BMR will go down since your fat & body mass will also go down.
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