The Energy Balance Equation

The Energy Balance Equation illustrates the relationship between the calories consumed (energy intake) and the calories expended (energy output).

ENERGY IN = ENERGY OUT +/- CHANGES IN BODY STORES

Energy in refers to the number of calories consumed each day.

Energy out refers to a person's Total Daily Energy Expenditure (TDEE), which can be further divided into Resting Energy Expenditure (REE) and Non-Resting Energy Expenditure (NREE).

As the name suggests, REE refers to the amount of energy you expend at rest, and consists of one element: Resting or Basal Metabolic Rate (R/BMR). The BMR refers to the amount of energy the body needs to perform basic functions, such as heart rate and breathing. These bodily functions are the greatest contributor to overall calorie expenditure, accounting for 50 to 70 percent of TDEE.

👉 NOTE: While the terms Resting and Basal Metabolic Rate are often used interchangeably as they both refer to energy expenditure at rest, it's important to note a technical difference in how they are measured by researchers. RMR will always be slightly higher because it is measured in a non-fasted state (your body uses energy digesting and assimilating food), whereas BMR is measured in a fasted state. In other words, your resting metabolic rate (RMR) is your BMR plus the number of calories you burn digesting food, the number of extra calories you burn after exercise, and other small bodily functions.

NREE contains three elements:

• Exercise Activity Thermogenesis (EAT): EAT is the amount of energy used to perform purposeful or planned exercise, such as a strength training or cardio session. EAT can range from 0% to around 50% of TDEE depending on the level of activity.
• Non-Exercise Activity Thermogenesis (NEAT): NEAT is the amount of energy used for the unplanned and low intensity physical activity of everyday life, such as walking to work, housework, and even fidgeting. Think of it as the activity that is necessary for you to get through your day.
• Thermic Effect of Food (TEF): TEF is the amount of energy utilized as part of food digestion and assimilation. The processes that facilitate these actions are small, but still significant contributors to the energy out component of the Energy Balance Equation. TEF accounts for roughly 10 percent of TDEE, assuming the diet is balanced. 
  • Protein digestion has the potential to burn 20–30% of its calories
    • Ex: 300 calories of pure protein consumed, around 60–90 calories are burned just through digesting it.
    • NOTE: Consuming protein from whole sources like meat, eggs, or dairy will impact thermogenesis to a significantly higher degree than consuming protein from powders, which likely has little to no thermogenic effect.
  • Fat digestion can potentially burn ~5% of its calories
    • Ex: 300 calories of pure fat consumed, around 15 calories are burned through digesting it
  • Carbohydrate digestion can potentially burn 5-10% of its calories
    • Ex: 300 calories of pure carbs consumed, around 15–30 calories are burned just through digesting it

In the context of weight loss, we can classify resistance training and formal cardio (structured workouts deliberately performed as part of a training program) as EAT, and everything else (including step goals) as being NEAT. Ultimately, the exact breakdown doesn’t matter because we're interested in estimating the Total Daily Energy Expenditure.

Changes in Body Stores refers to the adjustment — up or down — that the Energy Balance Equation makes to fat mass (FM) and lean body mass (LBM).

When energy-in exceeds energy-out, the body balances the equation by storing the excess energy (calories) as a combination of FM and LBM. Conversely, when energy-out exceeds energy-in, the body balances the equation by breaking down FM and LBM to release the extra energy it needs. The Energy Balance Equation must always balance which will be realized by bodyweight or body composition going up or down.

It is important to note that we can't always rely on the Energy Balance Equation to accurately predict changes in bodyweight as it is an oversimplification of complex physiological processes. The equation doesn't take into account the adaptive nature of metabolism which can alter requirements. Nor does it address factors that affect water balance, like stress, glycogen levels, inflammation, and the female menstrual cycle can affect bodyweight independent of what changes may be occurring to FM and LBM.

Interpreting the Energy Balance Equation

Energy balance refers to a state where the amount of energy coming into the body is equal to the amount exiting. When in a state of energy balance, there is no change to the body's energy stores, which is generally referred to as maintenance. However, imbalances often occur that prompt changes in the body's energy stores in one of two ways.

1. Positive Energy Balance refers to a state in which energy intake exceeds energy output, which can be understood as an energy surplus. This results in the extra energy needing to go somewhere, as energy cannot be destroyed, so the body stores it as a combination of FM and LBM.
2. Negative Energy Balance refers to a state in which energy output exceeds energy intake, which can be referred to as an energy deficit. When the body needs extra energy because of deficits in intake or through the production of extra output, the body must breakdown and rely on stored energy in the form of FM and LBM.

When creating an effective energy balance strategy, it's essential to keep the goal in mind as it will determine whether to establish an average energy balance that is Positive, Negative or at Maintenance (Neutral).

• For Fat Loss: The goal is to create a negative energy balance. This is achieved when the average energy expenditure (calories burned) exceeds the average energy intake (calories consumed).
• For Muscle Gain: The goal is to establish a positive energy balance. This means that the average energy intake must be greater than the average energy expenditure.
• For Maintenance: To maintain current weight, ensure that the average energy intake equals the average energy expenditure.

The successful implementation of each energy balance strategy hinges on calculating the average caloric intake over a seven-day period. For example, if an individual maintains a small energy deficit for five days of the week, but spends the other two days indulging in an excessive energy surplus, it's likely that their weekly average energy balance will result in a net Positive. Conversely, if an individual creates a significant energy deficit for five days and only a slight surplus on two days, the overall weekly energy balance will likely be Negative.

Putting together a Nutrition Plan

When setting out to create an initial Nutrition Plan for a client, no matter how precise the intake process, it will always be a "best guess" scenario. As a result, the initial Nutrition Plan should be seen as a starting point from which adjustments will need to be made based on the progress of the client. The next step will be taking this initial "best guess" and provide it to the client, help them follow it, monitor their progress (bodyweight, body fat, pictures, circumferences, and direct feedback), and then make changes that will best keep the client progressing towards their stated goal.

How to Estimate Maintenance

Remember that Maintenance refers to a state where energy intake (from the consumption of food and drink) is equal to energy output (from BMR, TEF, EAT, and NEAT). This becomes necessary to know if we wish to achieve a fat goal because an energy deficit will need to be achieved. However, without an accurate estimate of maintenance, you have no context for what constitutes an energy deficit. The most accurate approach to estimating maintenance is to track energy intake (food and drink) and bodyweight over a period of time, e.g., two weeks. Unfortunately, this is time consuming, and an accurate enough figure for energy expenditure can be found using the four components of TDEE: BMR, TEF, EAT, and NEAT.

Estimating Basal Metabolic Rate (BMR)

The BMR can be influenced by a variety of factors, most notably LBM. Generally, a larger body mass correlates with a higher BMR, but the composition of that mass plays a key role. If a greater percentage of your body mass consists of muscle, you will burn more calories due to muscle's higher metabolic rate.

Consider this: your body expends approximately 6kcal per pound each day to maintain its current LBM. By contrast, FM is less metabolically active, requiring only around 2kcal per pound. This doesn't mean fat is inert. In fact, it performs several important functions, including hormone production. So, while LBM, particularly muscle mass, has a greater impact on BMR, both components contribute to your body's energy needs.

There are several established formulas for estimating BMR. The majority of these formulas use respirometry data as their foundation, which involves analyzing the combination of gases exhaled in a person's breath to measure their energy needs. These formulas then incorporate variable like height, age, and gender to provide a more accurate estimation. A 2005 review found that the Mifflin-St Jeor equation to be more accurate than the Harris-Benedict, Own and WHO/FAO/UNU equations, however neither of these factor in body composition (LBM vs FM) when determining BMR. On the other hand, the Katch-McArdle equation does consider body composition, making it more accurate for our purposes of achieving positive body composition changes. Additionally, because most of the difference between a man's and a woman's BMR is due to their amounts of lean mass, this equation will work for both men and women.

The Lean Body Mass amount can be pulled from InBody, however if for whatever reason you do not have access but know the Total Weight and Body Fat %, you can calculate it from the following equation:

Estimating Activity:

Exercise Activity Thermogenesis (EAT) & Non-Exercise Activity Thermogenesis (NEAT)

Accurately estimating energy expended through EAT can be difficult as it can have a high amount of variability based upon:

• The nature or selection of the workout. For example, there will be more energy expended during a lower body workout than training shoulders or arms, simply due to the fact that the muscle of the lower body are larger and therefore take more energy.
• The physical capacity of the individual. For example, a professional athlete will expend more energy during training than a gen-pop client, regardless of their training age, this is due to the athlete knowing how to utilize intensity (whether through load selection or effort) to complete their workout.

The amount of energy expended through NEAT can also be challenging to estimate, as a large part of it is subconscious — e.g.; fidgeting when bored or shivering when cold. It is also extremely variable and affected by factors that are largely out of an individuals control, such as the environment and seasonal variation.

Because both EAT and NEAT both come with unique set of challenges for accurate estimation, it is best to group them together and estimate total activity levels based on an activity multiplier.

Activity multipliers express a person's total activity level as a number, encompassing daily steps (including cardio), body composition level, total daily protein intake, and an assumption of 3 training sessions a week. 

For clients without a weight loss goal: start with a baseline of 1.1 for the Activity Multiplier to represent a sedentary lifestyle. Then, based on the information provided by the client, adjust this number using the values from the chart above. Finally, multiply the adjusted multiplier by the estimated Basal Metabolic Rate (BMR) to calculate the estimated Total Daily Energy Expenditure (TDEE).

For clients with a weigh loss goal: The client's caloric intake for the initial two-weeks will be based solely off their Basal Metabolic Rate (BMR) and a maximum Activity Multiplier of 1.1. To apply additional Multipliers you will need to calculate their average daily step count and protein intake using Trainerize, as well as any progress made with body composition using the InBody during their first two-week check-in. Based on the data collected, appropriately adjust the Activity Multiplier using the values from the chart above. This will not only jumpstart weight loss but it will incentivize clients to use the Thesis app to track.

Estimating Thermic Effect of Food (TEF)

The Thermic Effect of Food signifies the energy that the body utilizes to process the food we consume — from digesting and absorption to its eventual utilization and storage. Each macronutrient, as we've discussed earlier, presents its own unique TEF value. Specifically, the process of metabolizing proteins, carbohydrates, and fats requires approximately 20-30%, 5-10%, and around 5% of the energy content of these nutrients, respectively.

To avoid having to work out TEFs for each macronutrient on a meal-by-meal, a quick estimate is that TEF accounts for roughly 10% of total calorie intake. So, if a client eats 2,000 calories of a relatively balanced diet, meaning that it is not massively skewed in the direction of any single macronutrient, then TEF will be around 200 calories. While this is interesting to know, the myopic and tedious nature of this calculation is likely more trouble than it's worth. As a result, we should view TEF as a relatively minor constant variable than isn't necessary to factor into the initial caloric estimation.

Establishing a Deficit

Once the estimated TDEE has been established, the next step is to calculate a calorie target that creates an energy deficit for the client. The size of this deficit will be guided by the timeline set to achieve the goal.

In the above example, the client whose BMR is calculated at 2000 calories is consuming 1500 calories from food and drink, but is expending 2000 calories per day through the combination of factors that make up TDEE which creates a 500 calorie energy deficit. To make up for the difference in energy requirements, those 500 calories are then taken from the body's energy stores of FM or LBM.

Just like each macronutrient has different energy densities (proteins/carbohydrates at 4kcal per gram and fat at 9kcal per gram), so do the different body tissues. One pound of muscle likely around 600-800 calories, but we always want to mitigate the loss of muscle mass when dieting. Alternatively, one pound of adipose tissue (a.k.a. fat) contains around 3500 calories. Theoretically, if a 3500 calorie deficit can be created, one pound of body fat will be lost. Because 3500 calories divides nicely by 7 — as in 7 days in a week — the 500 calorie per day deficit is often seen as the default number to start with when setting up a deficit.

• A daily deficit of 500 kcal would theoretically produce one pound of fat loss per week.
  • 500 x 7 = 3500 kcal
• A daily deficit of 1000 kcal would theoretically produce two pounds of fat loss per week.
  • 1000 x 7 = 7000 kcal

The '3500 kcal' rule is a helpful tool to illustrate the theory behind energy balance, but it's important to be aware of its limitations. It is important to understand that it is an oversimplification of the dieting process because the composition of weight loss will never be 100% body fat and varies according to:

• Body Fat %: As body fat decreases, the risk of losing LBM increases because there is less FM to fill the energy deficit.
• Resistance Training: Given the same energy deficit, somebody who trains will retain more LBM than someone who only diets and doesn’t train. When people diet without resistance training, they tend to lose a mixture of fat and muscle. On average, for most dieters who do not use resistance training as part of their weight loss strategy, 25 percent of the weight the lost is lean muscle tissue.*
• Macronutrient Ratio: Given the same size energy deficit, somebody who follows a high protein diet will retain more LBM than somebody who follows a low protein diet.

When in a deficit, the body will use a combination of FM and LBM to satisfy the energy deficit. And, the greater the deficit, the greater likelihood there will be to losses to both FM and LBM.

Deficit Size – Small. Medium. Large.

When it comes to deciding on a deficit size, it is important to take into account the following:

• Body Composition: What is the overall body composition (FM vs LBM)? How can we best manage the risk to LBM loss?
• Timeframe: How long does the client have to achieve their goal? What is the required rate of progress?
• Adherence: What size deficit can the client adhere to? Are there going to be any outings, events, or holidays that will need to be accounted for?

Small Deficits: 10-15%

• Non-invasive and easy to implement, which can increase adherence. For instance, substituting a high-fat protein source such as Ribeye steak with a lower-fat option like turkey breast can effortlessly create a 200kcal deficit.
• Minimal to zero interference with your training regimen, ensuring optimal performance remains uncompromised.
• Greater likelihood of preserving muscle mass during the dieting process.
• The pace of fat loss may be slower, which can pose challenges for shorter deadlines, but an extended timeline can allow for proper eating habits to be established for overall long-term health.
• If the Total Daily Energy Expenditure (TDEE) is overestimated, it could result in a 10% deficit falling short of establishing a substantial energy deficit.
• Smaller deficits run the risk of being entirely offset by minor dietary deviations, thereby neutralizing the energy deficit.
• This method is particularly effective for lean individuals proficient in tracking their food consumption and not constrained by impending deadlines.

Moderate Deficits: 20-25%

• The pace of fat loss is significantly expedited compared to smaller deficits, ensuring more rapid results.
• Tolerance for errors in Total Daily Energy Expenditure (TDEE) estimation is higher, providing a buffer against inaccuracies.
• For the most part, it maintains the integrity of training performance, causing minimal to no disruption.
• If there is a strict deadline, the rate of fat loss might not be fast enough.
• Ideally caters to a balanced or 'middle ground' approach, striking the right balance between speed and sustainability in weight loss.

Large Deficits: 30-50%

• Maximizes the rate of fat loss, making it an excellent fit for short-term timeframes.
• Most disruptive to everyday life, and difficult, if not impossible, to sustain longer term.
• Unrealistic deficits can lead to feelings of guilt and foster a negative mindset due to frequent failures.
• As the size of the deficit grow, so does the proportion of weight loss from Lean Body Mass (LBM).
• Ideally suited for experienced dieters with conscious nutritional habits aiming for short-term goals, such as getting in shape for the beach or a photoshoot.

Putting it all together

Step 1: Use the InBody to get a starting point for the clients Body Weight, Body Fat%, and Lean Body Mass.

Step 2: Find the clients estimated BMR using the Katch-McArdle formula:
- BMR = 370 + (9.8 x Lean Body Mass)

Step 3: Calculate the clients estimated TDEE. Refer to the Activity Level chart to select the multiplier that best represents the client to find maintenance calories.
- BMR x Activity Multiplier = Estimated TDEE

Step 4: Select a Deficit you would like the client to start with based on their goal and timeline.
- Small 10-15% — Moderate 20-25% — Large 30-50%

Step 5: Subtract the estimated TDEE by the Deficit amount to establish the new Daily Calorie Goal.
- Estimated TDEE – XX% = Daily Calorie Goal

Example 1:

Ori is a 29 year old male who weighs in at 210lbs, with 25% Body Fat and a Lean Body Mass of 158. His occupation involves sitting at a desk most of the day from Monday to Friday. And his physical activity consists of playing golf on the weekends.

First, we will need to find Ori's BMR using the following equation:

• 370 + (9.8 x Lean Body Mass) = BMR
• 370 + (9.8 x 158) = 1918 kcals

Ori's BMR is 1918 kcals

Next, we need to calculate Ori's estimated TDEE using the Activity Level chart. Based on Ori's current body fat level of 25% and the fact that he currently averages under 5,000 steps while a day consuming roughly 85 grams of protein daily, his Activity Multiplier is 1.15. Using the following equation, we will figure out the maintenance calories.

• BMR x Activity Multiplier = Estimated TDEE
• 1918 x 1.15 = 2205 kcals

Ori's estimated TDEE or Maintenance calories are 2205 kcals

Now, we will have to select a Deficit. Based on our initial conversation, he wants to look good for the summer but also wants something sustainable, so as not to be too conservative we will select a deficit of 20%. Using the following equation, we will establish his new Daily Caloric Goal.

• Estimated TDEE – XX% = Daily Calorie Goal
• 2205 kcals – 20% = 1764 kcals

Ori's new Daily Caloric Goal is 1764 kcals, which will allow him to lose weight at a rate of ~0.88 pounds per week.

To calculate the rate of change, subtract the Daily Caloric Goal (1764 kcal) from the Maintenance Calories (2205 kcal) to get a Daily Caloric Deficit of 441 kcal. Now multiply this by 7 (days in a week) to get the Weekly Caloric Deficit of 3087 kcal. With the knowledge that it takes a weekly caloric deficit of 3500 kcal to lose one pound a week, we can simply divide 3087 by 3500 to get a 0.88 pound/s rate of change per week.

Example 2:

Lauren is a 41 year old female who weighs in at 160 pounds, with 31% Body Fat and a Lean Body Mass of 110. Her occupation involves running errands most of the day from Monday to Friday. And her physical activity consists of drinking with her friends on the weekends.

First, we need to find Lauren's BMR using the following equation:

• 370 + (9.8 x Lean Body Mass) = BMR
• 370 + (9.8 x 110) = 1448 kcals

Lauren's BMR is 1448 kcals

Next, we need to calculate Lauren's estimated TDEE using the Activity Level chart. Based on the fact that she is fairly active during the week, consistently averaging around 10,000 steps a day and consumes over 100 grams of protein daily, her activity level is 1.4. Using the following equation, we will figure out the maintenance calories.

• BMR x Activity Multiplier = Estimated TDEE
• 1448 x 1.4 = 2027 kcals

Lauren's estimated TDEE or Maintenance calories are 2027 kcals

Now, we will have to select a Deficit. Based on our initial conversation, Lauren will be a bridesmaid at her friend's wedding and wants to outshine her much smaller friend because she called her fat. Based on her goals she needs to lose 20lbs in 3 months, which will require at around a pound a week drop or 1% per week over the next 12 weeks. Due to the nature of the goal and the timeline at hand, we will select a deficit of 30%. Using the following equation, we will establish her new Daily Caloric Goal.

• Estimated TDEE – XX% = Daily Calorie Goal
• 2027 – 30% = 1419 kcals

Lauren's new Daily Caloric Goal is 1419 kcals, which will allow her to lose weight at a rate of ~1.2 pounds per week.

To calculate the rate of change, subtract the Daily Caloric Goal (1419 kcal) from the Maintenance Calories (2027 kcal) to get a Daily Caloric Deficit of 608 kcal. Now multiply this by 7 (days in a week) to get the Weekly Caloric Deficit of 4256 kcal. With the knowledge that it takes a weekly caloric deficit of 3500 kcal to lose one pound a week, we can simply divide 4256 by 3500 to get a 1.2 pound/s rate of change per week.