In nutrition, calories are the amount of energy we consume from food or the amount of energy we expend during physical activity
As you will learn later, each macronutrient also carries with it a different caloric load:
As a nutrition coach, your work with calories will be to help individuals understand what an appropriate caloric intake is for their goals. While ultimately you will likely be providing a macronutrient based prescription, everything will start with calories!
To help your clients with an appropriate caloric prescription let’s start with understanding metabolism – or the total amount of energy required for each of our physiological actions.
Basal metabolic rate is the number of calories required to keep your body functioning at rest. Picture yourself sleeping after not having consumed a meal in a while. Your essential functions – breathing, heart beating, cellular activity – are all still happening as a result of your basal metabolic rate.
The only truly scientific way to measure BMR would be to lay in an environmental chamber after fasting, but obviously that is not practical.
For your work, it is recommended that we use the Harris Benedict Formula to find a client’s BMR. This formulas has undergone three revisions since its inception in 1918 and 1919. The most current formula is as follows:
MEN: BMR = (10 x weight in kg) + (6.25 x height in cm) – (5 x age in years) + 5
WOMEN: BMR = (10 x weight in kg) + (6.25 x height in cm) – (5 x age in years) – 161
Resting Metabolic Rate is actually what most people mean when they say the words “basal metabolic rate.”
Like BMR, RMR is measured at rest but it does not require any of the “extreme” conditions that BMR does (fasted, etc.).
If we looked at an individual’s RMR and BMR we would likely see very little variance
RMR defined – the amount of energy required to stay alive with no activity.
Obviously, actual metabolic rates will be much higher as none of us are simply living without any activity.
Factors that can affect RMR:
Can RMR be changed? Studies have repeatedly shown that RMR can NOT be changed per unit of fat free mass. For this exact reason the goal of every body composition oriented dietary process should be to retain as much lean tissue as possible while reducing body fat.
The predictive measurements for RMR (formulas instead of indirect calorimetry) are the same as BMR.
The Harris Benedict equation proved to be the most accurate so it will continue to be the recommended formula until proven otherwise. (Note, this study was also looking at type of work performed by the individual. While we are not focusing on that, it is important to note all variables when discussing research.)
Perhaps the simplest part of nutrition, caloric intake is quite obviously the number of calories consumed by an individual from food and drinks.
However, let’s remember a very important part of caloric intake – The Thermic Effect of Feeding or TEF.
Ever broken out into a sweat halfway through a very high calorie meal? You have experienced TEF.
Thermic effect of feeding, also known as dietary induced thermogenesis, is defined as “the amount of energy expenditure above resting metabolic rate due to the cost of processing food for use and storage.”
While exercise can actually affect the TEF, it is negligible. The main factors affecting the thermic effect of a meal will be total caloric load and macronutrient composition. Fats and carbohydrates will have an impact of 5-15% of the energy consumed burned through processing, with protein being at 20-35%.
Understanding TEF can have great implications on both fat loss and muscle gaining for individuals. As fat loss diets become more calorically restrictive, leveraging the TEF of protein can be of great advantage. Conversely, for someone with difficulty gaining weight, understanding that a higher protein consumption may actually be negatively affecting their caloric utilization is also very important to understand.
Caloric expenditure is an important part of the energy balance equation. Regardless of whether the goal is to lose fat, build muscle, or perform on a higher level – caloric expenditure must always be accounted for.
We can break expenditure down into two categories:
• Non-Exercise Activity Thermogenesis (NEAT) • Exercise Activity (EA) Thermogenesis (EAT)
Non-exercise activity thermogenesis is the energy expended for everything we do that is not sleeping, eating, or exercising. This can include simple things like walking to work, cleaning the house, mowing the lawn, and even something as small as tapping your leg or fidgeting.
NEAT is also part of the metabolic adaptation process. Chronic underfeeding will reduce NEAT and chronic overfeeding tends to increase NEAT. This is logical as when we feel deprived and underfed our desire to move is diminished. Conversely, we feel the need to “burn off” any excess food after a large overfeeding.
NEAT has been estimated recently to range from 10-50% of the energy balance equation.
NEAT seems to be the reason for some individuals being “naturally lean.”
Exercise activity accounts for the energy used during purposeful activity or exercise like working out, going for a run, or any other intentional calorie burning modality.
This number, when combined with NEAT, TEF, and RMR, will help yield your total daily energy expenditure.
While exercise is important, it is usually less than 30% of the energy balance equation. Different types of exercise will yield different results from a calorie burning and metabolic perspective. It is very important to understand the primary fuel source for each activity that is being performed.
Aerobic training will yield a higher number of calories burned during the activity. This is due to the steady nature of the activity with a sustained effort the entire time.
During aerobic training the body is able to use fat as fuel. It will primarily involve the use of slow twitch muscle fibers, the energy demands of which are slower and easily met by fat.
Aerobic training will ultimately lead to our bodies adapting in a manner that leaves us storing more fuel in the form of intramuscular glycogen and triglycerides.
Anaerobic training is fueled by anaerobic glycolysis and will typically burn less actual calories during the session than aerobic training. However, due to EPOC (excess post-exercise oxygen consumption) and other training factors, the body will continue burning for several hours (and in extreme cases, up to 2 days) after the session has concluded.
Fast twitch muscle fibers will be the main fibers used in anaerobic training – these fibers use glycolysis as the main energy pathway. Glycolysis, as you will learn in the next chapter, is fueled by carbohydrate.
It is important to note that while we are using carbohydrates during anaerobic training, we are able to burn fats in the “after window.”
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