Table of Contents
In lesson 1 we learned about our TDEE (total daily energy expenditure) and its components. Here we will learn how to estimate our TDEE. In the next lesson we will see how to use this information to guide the dieting process to help achieve a healthy body weight.
There are several different practical methods to estimate our TDEE, all of which are imprecise. However, this still serves as a useful starting point; in the next lesson it will become clear how to deal with the inaccuracy.
Calculating our TDEE with formulas
Several formulas have been derived to estimate one’s TDEE. These typically estimate your basal metabolic rate (BMR) and then multiply that by an activity factor based on your lifestyle. A few of these formulas include the Harris-Benedict equation, the Mifflin-St. Jeor equation, and the Katch-McArdle equation. Katch-McArdle depends on your lean body mass (LBM), not total weight, so you need to be able to estimate your body fat percentage to use this. Practically speaking it does not matter which you use as you are simply generating an estimate. If you’d like to use one of these calculators, simply google “TDEE calculator” and choose any of the available links. At the time of me writing this there is a compilation of different formulas here.
Note: There is one calculator I want to particularly draw attention to, and that is the NIH body weight planner. This will estimate how many calories we need to eat daily to reach a goal weight by a goal date. The calculations are based on group averages; due to all of the variability discussed in Lesson 1 the specific numbers it proposes may not be fully accurate. However, as we only need to generate an estimate, this does the trick and can be quite informative.
Example: Using the NIH body weight planner, enter:
- starting weight 225 pounds
- height 5’6″
- age 30
- physical activity level of 1.6
Set a goal weight of 180 pounds with a goal of achieving this in 1 year. Click on the “Calculate” button when it asks how you will change your physical activity. Place two entries, one for walking at a medium pace 3 times a week for 20 minutes and one for running at a medium pace 3 times a week for 20 minutes.
Entering this it tells us that to maintain our current body weight without changing our physical activity level we need to consume 3,080 calories/day. This is our estimated current TDEE. It tells us that if we eat 2,542 calories/day then we will reach our goal weight of 180 pounds in 1 year. After reaching it we can increase to 2,860 calories/day to maintain this new body weight. The increase is due to several of the concepts discussed in Lesson 1; when we are no longer losing weight the adaptive thermogenesis abates, non-exercise activity thermogenesis (NEAT) will likely increase to a small degree, and our thermic effect of feeding (TEF) goes up slightly when we increase calories.
By switching to expert mode a data table shows the expected body weight every single day over a year. Notice that 1.5 pounds is lost in the first two days, this is presumably due to a decrease in sodium intake, glycogen stores in the body, and the associated water. This is common when starting a diet and is one of the reasons the Atkin’s diet became so popular; a low carbohydrate diet will cause a large loss in water weight the first few days. Without knowing better you may assume you are losing body fat when you are actually losing water weight.
Importantly, look at the graph (reproduced below). A final body weight of 180 pounds is expected, but the margin of error includes 161 to 198 pounds. This reflects the individual variability alluded to previously and again indicates we are dealing with estimates, not exact calculations. You can click on the “Body Fat %” tab to see how this will change over time but this calculator assumes no resistance training is done; if you incorporate resistance training (which I strongly recommend) this will likely decrease further. If you click on the “Intake & Expenditure” tab (reproduced below) you will see how our TDEE will decrease over time. This occurs due to loss of body fat, loss of LBM, adaptive thermogenesis, and a decrease in NEAT. You can click on the “Advanced Controls” button and “Lifestyle Change” tab to see the impact of additional changes if you would like.
Graphs using input data from the above example
This graph shows expected body weight with range of uncertainty over time.
This graph shows how TDEE (red line) changes over time. The blue line represents calories consumed daily, which is assumed constant.
Calculating our TDEE by counting calories
If we are maintaining our weight over an extended period of time (ie, weeks), then we are roughly consuming the same number of calories that we burn daily, and our average caloric intake is equivalent to our TDEE. We can count all of the calories we eat, and that will give us the answer. To do this, I recommend for 3 typical days of eating to write down every single thing you eat and drink, record the total number of calories, take the 3 day average, and use this as an approximation of your TDEE. If you normally eat differently on weekdays and weekends then make sure to include at least one weekend day.
Tip: If you decide to record items you eat & drink I suggest keeping a pencil and piece of paper with you to record these throughout the day rather than risk misremembering later. You can look up the nutrition content at the end of the day. If nutrition labels are available you can write down the nutrition facts while you eat the foods but it may be difficult to do this discretely in a public setting if this is a concern. Alternatively, you can take pictures with your phone or send text messages to yourself of everything you consume. Nutrition labels can be found with google or through https://nutritiondata.self.com/, and you can record things with Excel or by hand. Apps can be used for this purpose as well (see below), and they may have the advantage of helping you track the various macronutrients and micronutrients in addition to calories.
Potential pitfalls when counting calories
It can be easy to forget to record all items you consume. If you go to the kitchen and eat a cookie, you need to include it. Cooking oil used for food preparation should be included. If somebody brings cookies to work and you eat one that also counts. You need to include any beverage that has calories as well. For people who have a tendency to eat mindlessly and not even realize it, this can be especially challenging.
In addition to recording what you consume, you need to record the quantity. This can be surprisingly difficult. In general if a nutrition label is available you should trust the label. Meat should be weighed prior to cooking assuming the nutrition label does not specify cooked. If you eat at a restaurant the listed calories can be significantly off. Restaurant calorie counts will likely be more accurate for food items that are weighed (ie, steak) or mass produced (ie, McDonald’s cheeseburgers). For an item such as chicken pasta alfredo the amount of alfredo can vary considerably and this can significantly impact the total calorie count. If you are eating a mixed dish prepared by others tracking this can be tricky. You can ask for the recipe and estimate the amount you consumed but do realize this can be prone to error.
Tip: Using food weight is generally more accurate than food volume for solids. A kitchen scale measuring in grams is very helpful and can generally be found for <$15. For example, a container of cottage cheese may state 1 serving is ½ cup and weighs 113 grams. However, if you measure out ½ cup and then weigh it this may weigh ~140 grams. This would lead to 24% more calories being consumed than expected.
Here's a quick visualization showing it can be difficult to estimate quantity by eye
The slice on the left has 10 grams of peanut butter for 55 calories, the slice on the right has 30 grams of peanut butter for 165 calories.
Even if you quantify everything accurately nutrition labels can legally be off by up to 20%. Occasionally they are off by more. A lot of this error will cancel itself out and thus this is not a huge concern but merits mention.
For all of these reasons, tracking calories will generate an estimate and may not be completely correct.
Note: There have been many studies showing that people as a whole do a poor job of estimating the number of calories they consume. This has been seen in registered dietitians(Champagne, 2002) as well as the general public in several large studies.(Freedman, 2014; Park, 2018; McKenzie 2021) Generally, people with more weight to lose under-report their caloric consumption to a greater degree. Anecdotally, many people think they are on a very low calorie diet and not losing weight; in reality many of these people are underestimating the number of calories they are consuming.
While not the topic of this nutrition course, if curious, misreporting is also frequent with physical activity.(Sharifzadeh, 2020)
Tracking calories gets easier with time
So how much time does it take to track all of these calories? If you have never tracked calories, macronutrients (protein, carbohydrates, fats), or micronutrients (sodium, potassium, etc), this seems like a monumental task when first starting. Initially it can take time to find foods in the databases and figure out how to scan things properly. It can seem like a nuisance to do this when eating out and estimating what is in a certain meal. However, most people eat most of the same foods on a day-to-day or at least week-to-week basis. Thankfully, after recording foods or meals once you can simply pick that same selection when you eat the food again and that saves a lot of time. Once you do this for a few days to a week it becomes much easier and faster.
Tip: There are several apps to aid in tracking calories and other nutrients. One example is MyFitnessPal. If you are tech savvy, I suggest installing it (or a different app of your choice) and experimenting; you can easily scan barcodes from packages to upload nutrition content once you get the hang of it. Another app I will mention is Cronometer, which is free and can do a more comprehensive job of compiling micronutrients (micronutrients are discussed in Lesson 9). Feel free to try several apps and see which one you prefer. The food databases are another source of potential pitfalls; entries may not exactly match what you are eating and may be inaccurate if uploaded by casual users incorrectly.
Do we need to estimate our TDEE and/or track calories?
So when should we even calculate our TDEE? Remember, all of the above methods provide an estimate. As shown in Lesson 1, when we change how much we eat and our exercise habits this will alter our TDEE; the calculators cannot fully account for this on an individual level due to individual variability. My recommended approach is to estimate your TDEE one time when starting the dieting process for the purpose of losing or gaining weight. In the next lesson I will go over how to use this number. For people who are happy with their current body weight estimating their TDEE is less useful.
Do we even need to track calories? Lots of people gain muscle, lose fat, and live healthy lives without doing so. If you are happy with your weight without ever having tracked calories there is no need to start now. For people who want to lose or gain weight they can first attempt to do so by making healthy changes (tips discussed in upcoming lessons) and see where this leads. If good progress is made then there is no need to start tracking. However, if at some point progress stalls and it is not clear what is going wrong, counting calories can be immensely helpful to get on track. Additionally, one of the biggest predictors of weight loss success is initial weight loss; if your initial efforts are not working within a few weeks it is important to re-evaluate your strategy sooner than later, and tracking calories for a short time can help jump-start progress.(Chopra, 2021)
Tip: A good first step if simply trying to eat healthier is to prioritize unprocessed food intake. This has been shown to naturally decrease the amount of calories consumed in a day (potentially due to a greater satiating effect from relatively higher fiber and protein content as well as the need for a greater amount of time spent chewing(Appleton, 2021)) and is associated with better weight outcomes.(Hall, 2019; Askari, 2020) This also can lead to better health outcomes when looking at a variety of different health conditions, at least in adults.(Lane, 2021; Pagliai, 2021)
Use caution if concerned for disordered eating
CAUTION: Some people may find that tracking calories triggers disordered eating or has other negative impacts on their mental health. If this is a concern then I recommend not tracking calories. Excellent progress can be made by sticking to general healthy eating principles, and I will discuss how to do this in upcoming lessons. If one begins tracking calories without problems but then realizes they are developing concerning habits or behaviors (ie, becoming too restricted regarding food intake, fearing social gatherings due to available food, following binge-restrict cycles to “make up” for excess calories one day by restricting severely on the next, etc), then it is extremely important to stop tracking immediately and to consider consulting one’s healthcare provider to discuss how to proceed in a healthier manner.
Estimating your TDEE with the above formulas is relatively straightforward. Considerably more effort is required to estimate your TDEE with calorie counting. Anecdotally, many people struggle with weight loss until they begin tracking calories and developing this skill can be a worthwhile endeavor. For people who do not wish to make counting calories part of their regular lifestyle, tracking for short periods of time when attempting to troubleshoot the dieting process (when desired weight loss or gain is not happening) can be an effective compromise. Bottom line, whether or not to track calories is a personal choice but can be a very enlightening and effective tool when used appropriately.
In the next lesson we will discuss how to determine a healthy body weight goal (if desired), how to use the the TDEE estimate to determine caloric intake (if desired) and how to track progress over time (regardless if we are tracking calories or not). This will then allow you to make adjustments as needed to continue moving closer to your goals.
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