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Physiology Fundamentals: Back To Basics.

Different Metabolic rates(BMR, RMR,..) and how to Calculate Daily Energy(calorie) Requirements and Expenditure. Part 1.

Check out the Part 2 & Part 3 of this Series!

Basal metabolic rate (BMR) is technically the absolute minimum amount of energy needed by your body to sustain its vital functions while sleeping so it's often referred to as SMR (sleeping metabolic rate) too. Most studies measure resting metabolic rate (RMR) instead. RMR is our awake & resting on a bed metabolic rate and generally is 10% greater than true BMR.

Since we spend more time awake and active plus more research data is available for RMR we'll focus on it from here on, adding on to it other energy expenditure variables to get an accurate estimate of our daily energy expenditure (DEE) number. Now, why we need a Daily Energy Expenditure number at all?? Well, because this simple law of thermodynamics holds true for every dynamic system in the universe and hence for our bodies as well: Energy in = Energy out + Change in energy store.

Energy in is the food you consume in a 24 hour period in terms of calories (total calorie intake), Energy out is the Energy you spend daily (DEE), and change in energy store is the constant flux of Storage and Oxidation(burning in presence of oxygen) of nutrients in and out of our tissues.
The energy equation in more familiar terms : Energy Store (fat + lean tissue) = Energy In (daily food intake) - Energy Out(daily energy expense aka DEE). Say, if intake is 5 and expense is 4, there is a positive balance of energy (5-4 = 1), that 1 unit of extra energy goes to synthesizing new tissue, you gain weight. If the Intake is equal to expense you remain in energy balance ( 5-5 = 0) aka homeostasis, you neither gain nor lose weight. Similarly, a negative energy balance where your food intake is not enough to provide for your daily energy expense will result in our body oxidizing tissue to fill the energy Gap. 4 - 5 = -1; that 1 unit of energy has to come from somewhere and it will come from our own bodily tissues.

If there is an excess of energy, Glycogen stores get filled, fat gets stored in fat cells, muscle tissues and Organs get repaired. If there is more energy expenditure than energy intake the difference comes out from our energy stores (fat cells/glycogen/lean tissue) i.e. we lose tissue/fat/weight. For a detailed take on oxidation and storage of nutrients read Assimilation, Storage & Oxidation of Protein, Carbs and Fat.

Physiological knowledge help us to fine tune, predict and manipulate all of these variables with remarkable accuracy, the more we know the better because altering our Energy stores is the key to the strong and aesthetic physique all of us yearn for. Altering our energy stores is also known as recomposition (losing fat tissue and gaining muslce tissue). Bulk and cut? Yeah, these are controlled periods of energy access and energy deprivation ( positive and negative energy balance). So, to optimize the rate and magnitude of change in our energy stores we need to control the other two variables : Energy Intake and Energy Expenditure. Bascially we need to know with atomic precision how many calories we're eating daily or plan to eat plus how much energy/calories we're burning daily or plan to burn.

Energy intake is easy to calculate, just read the labels or a quick Google search about your favorite food items will give you the nutritional profile along with the Calorie per Gram number, do your math from there. An easier and more educated way to do that is to find out the exact protein, carb and fat content in Grams from the same sources of your daily intake and use the 3cal/gram for protein(yeah i know, you've read that it's 4 cal/gram. Keep Reading), 4cal/gram for carbohydrates, and 9 calories per gram figure for Fats. For example, if i eat 4 eggs and an apple daily in breakfast. One the first page of Google search result you can find that Egg has 5 grams of fat, 6 grams of protein, and zero carbs. Apple has 25 grams of carbs on the other hand.
nutritional profile of an applenutritional profile of an egg
Two valuable pieces of information is to be derived from here. 1) Total Intake of Protein, fat and carbs. 2) Total Calorie Intake. my breakfast has 25 grams of carbs(only from apple), 6x4 = 24 grams of Protein(from 4 eggs) and 5x4 = 20 grams of Fat. Total calorie intake of my breakfast is 25 x 4 + 24 x 3 + 20 x 9 = 352 Calories. There are different digestive efficiencies for protein, fat and carbs but unless you’re eating tons of fibers(fibers curtail digestive efficiency significantly, i'll adress that in an article about Salads specifically) it can be neglected or adjusted later. Read this series for in-depth information about MACROS (Protein, Carbohydrates and Fats) All about MACROS

Daily Energy Expenditure is the most complicated variable to be addressed here. We will grapple with the various aspects of it now. Bodybuilding magazines and mainstream media have oversimplified ideas about DEE, though. they give you a rough estimate of 15-16 x your body weight in pounds (lbs.) and the more "accurate" resources give you a figure of 12-14 x weight (lbs.) for RMR and instruct you to add unique multipliers to account for various activity levels, like 1.2 for sedentary, 1.4 for active, 1.6 for VERY active and 1.8 for Athletes. This is a better approach but still not as accurate as it should be. Imagine what would be the multiplier for a sedentary guy who also works out for one hour daily? Or a sales person who's walking all day and probably burning more calories than an athlete while at it?

you'll get these answers into the Part 2 & Part 3 of this Series!

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