In my previous blog post we talked about all the challenges associated with trying to estimate energy intake from the food we eat. On the surface it painted a bleak picture, no matter what method you chose to try and quantify like energy intake, calories, hand portions, the scale, or combinations of all three, ultimately there is no exact way to quantify your energy intake.
The discussion around energy intake becomes even more bleak because that is only half of the problem when it comes to calories and figuring out how much energy to consume. The other half is figuring out how much energy we are expending.
In this post we will look at energy expenditure, how to quantify it, and conclude how best to quantify it in order to reach your energy intake goals.
The most popular method to quantify energy expenditure is to use an online calculator.
Google metabolic rate calculator and you will get something like 86 million results…there is no shortage of calculators out there to use.
There are also different equations you can use to calculate your metabolic rate…there are even revisions and different versions of the same equation!!!
So which calculator is the best one to use? Every website is going to tell you theirs is the best, most accurate.
It is no surprise that researchers have tried to determine the accuracy of these calculators.
In a 2018 study (Accuracy and Validity of Resting Energy Expenditure Predictive Equations in Middle-Aged Adults, 2018) researchers looked at 26 different metabolic rate equations and compared the predicted metabolic rate from the equations to a direct measurement of the participants metabolism. This study was done in 73 healthy sedentary adults between the ages of 40 and 65, 53% of which were women.
Researchers found that depending on the demographic, equations could underestimate or overestimate resting metabolic rate by 150-400 calories per day on average. If a given equation had an error of 200 calories, that means it could be off by 50 calories in one person (which is quite reasonable) but off by 400 calories in another individual!
Let’s assume the best case scenario and say the equation is spot on for you. The next layer to this energy expenditure story is figuring out how much energy you expend through activity. THESE EQUATIONS ONLY ESTIMATE HOW MUCH ENERGY YOU BURN IF YOU WERE COMPLETELY STILL FOR 24 HOURS!!
Most calculators online will use what’s called an “activity multiplier” in order to figure out your total energy expenditure. It’s basically a number you use to multiply your resting energy expenditure with.
According to the United Nations Food And Agriculture Organization (FAO) (Human Energy Requirements, n.d.) here are the activity multiplies you can use.
Sedentary or light activity lifestyle
Active or moderately active lifestyle
Vigorous or vigorously active lifestyle
* PAL values > 2.40 are difficult to maintain over a long period of time.
If you are wondering how to determine what types of activities fall into each one of these buckets, the FAQ provides some clarification which I copied below.
Sedentary or light activity lifestyles. These people have occupations that do not demand much physical effort, are not required to walk long distances, generally use motor vehicles for transportation, do not exercise or participate in sports regularly, and spend most of their leisure time sitting or standing, with little body displacement (e.g. talking, reading, watching television, listening to the radio, using computers). One example is male office workers in urban areas, who only occasionally engage in physically demanding activities during or outside working hours. Another example are rural women living in villages that have electricity, piped water and nearby paved roads, who spend most of the time selling produce at home or in the marketplace, or doing light household chores and caring for children in or around their houses.
Active or moderately active lifestyles. These people have occupations that are not strenuous in terms of energy demands, but involve more energy expenditure than that described for sedentary lifestyles. Alternatively, they can be people with sedentary occupations who regularly spend a certain amount of time in moderate to vigorous physical activities, during either the obligatory or the discretionary part of their daily routine. For example, the daily performance of one hour (either continuous or in several bouts during the day) of moderate to vigorous exercise, such as jogging/running, cycling, aerobic dancing or various sports activities, can raise a person’s average PAL from 1.55 (corresponding to the sedentary category) to 1.75 (the moderately active category). Other examples of moderately active lifestyles are associated with occupations such as masons and construction workers, or rural women in less developed traditional villages who participate in agricultural chores or walk long distances to fetch water and fuelwood.
Vigorous or vigorously active lifestyles. These people engage regularly in strenuous work or in strenuous leisure activities for several hours. Examples are women with non-sedentary occupations who swim or dance an average of two hours each day, or non-mechanized agricultural labourers who work with a machete, hoe or axe for several hours daily and walk long distances over rugged terrains, often carrying heavy loads.
So maybe you can determine now which category you might fall into but which exact multiplier do you use? There is a range, do you fall in the low end of that range or the high end of that range?
As you can see there is a lot of room for error in using these calculators…I bet you are not surprised.
Could there be a more accurate way using technology?
The other common approach to trying to figure out how much energy you are burning is to use a wearable. There are lots of devices on the market today that you can wear on your body that track your activity. So while they might estimate your basal metabolic rate they should be more accurate in tracking your activity…right?
Unfortunately that doesn’t appear to be the case.
A 2020 study (Wrist-Worn Wearables for Monitoring Heart Rate and Energy Expenditure While Sitting or Performing Light-To-Vigorous Physical Activity: Validation Study, 2020) compared the energy expenditure calculated by Apple Watch Series 4, Garmin Fenix 5, Polar Vantage V, and the FitBit Versa with the actual energy expenditure across various activities from sitting to sprints. Researchers concluded none of the wearables produced accurate enough estimations of energy expenditure. The Apple Watch was off by 124 calories per hour. The Polar Vantage V was off by 121 calories per hour. The Garmin Fenix 5 was off by 131 calories per hour. The Fitbit Versa was off by 112 calories per hour.
UGH…even technology is failing us!
But wait…there is more!
The final way to assess caloric intake is to get a resting metabolic rate test as well as an active metabolic rate test. During these tests you wear a mask, both while laying down as well as while exercising at various intensities. A machine will then analyze the gasses you are inhaling and exhaling and can use that information to determine how many calories you are burning.
When you have tests like this done you will receive reports that look like this.
From this you know how many calories you are burning at rest and then how many calories you burn at various exercise intensities. Depending on the day and the physical activity you do you can get a decent idea of how many calories you are burning.
In my opinion the combination of an active metabolic test and a resting metabolic test are the most accurate way to try and quantify one’s caloric burn. That said, they are not perfect.
For one, these tests are not accessible to everyone. It can cost several hundred dollars to have these two tests done. In addition, the active metabolic test can be quite challenging from a physical activity perspective as well and would not be appropriate for someone who is not currently exercising.
Also not everyone is tracking their exercise intensity, and the zones listed in the sample image above may not mean anything to you, making this information not so useful.
Finally this data is a single point in time statement. What I mean by that is that as time passes the data may become less and less accurate. The amount of fat and muscle you carry around as well as dietary changes can all affect the calories you burn
Where does this leave us?
Using an equation to determine our basal metabolic rate could be accurate or it could be off by several hundred calories. In addition, since that number does not include calories burnt through activity we have to use an activity multiplier which can be vague and obviously shift from one day to the next.
Activity trackers are more personalized as they are tracking your physical activity throughout the day each and everyday, but they also appear to be off by at least 100 calories per hour of activity in some cases.
An active and resting metabolic test may be the most accurate way to determine our caloric burn, but it is not easily accessible for everyone.
All hope is not lost however. The good news is that we don’t need 100% accuracy as long as we have consistency.
Let me explain.
When I try to address the problem of energy expenditure for a client I use an equation to figure out their basal metabolic rate. Actually I look at several equations, and pick a nice middle ground between a few different ones.
Then I look at their activity and pick a conservative activity multiplier. I know that there will be days with more activity and days with less activity so I want to pick something that takes into account everything.
Using that I have a VERY rough total calorie burn for the day (I realize it could be off by several hundred calories). As I discussed in the last post, the client will also be tracking their food intake either by using calories or hand portions. In addition, we have the scale or other body composition metrics (tape measurements, or the tight pants test) at our disposal to track changes in body composition.
Now we have everything we need to try and hone in on a caloric intake that matches their goal…the only piece we are missing is consistency.
What do I mean by consistency?
We need to hold as many things in their lifestyle constant for as long as we can. I am not saying you need to be a robot and do the same thing day in and day out, but from week to week things look roughly the same.
You do the same workout routine from week to week.
You keep your steps consistent from week to week.
You follow the same sleep schedule from week to week.
Your meals from week to week look roughly the same.
We want to hold as many things that will affect the calories in and calories out equation consistent across several weeks.
This way, knowing that the numbers we are using are incorrect, at least they are consistently incorrect.
If the body composition metrics are moving in the right direction, great, we don’t need to change anything. However they likely won’t be after a few weeks, so we will adjust the food intake side of the equation in the direction we need to meet their goals. Then we just repeat the process until we start to get the results we want.
I know all of this is an estimate, I know it’s likely not accurate, but as long as it’s consistently inaccurate we can use it as a baseline to adjust what matters…your energy intake. Remember calories are just some made up way of quantifying energy, it’s arbitrary. That’s why hand portions can work just as well. We don’t really need to know calories, we just need a way to quantify energy.
Consistency is what is hard. Most people argue over how inaccurate calories are both from an intake and output perspective, but once you realize it doesn’t really matter if they are accurate or not it’s a bit freeing.
Trying to be consistent with your activity, sleep, and food tracking is the real hard part, but that shouldn’t be a surprise, the challenges people face with health and wellness always comes down to establishing healthy habits they can be consistent with. Being conscious of our energy balance is just another health habit that we need to work at. We need to find a methodology of tracking that we can be consistent with.
The value of tracking energy intake and output for a while is that keeping an eye on your energy balance can become intuitive. After a while you don’t need to pay attention to calories, or how big something is compared to your hand. You can just look at your plate and say, that looks about what I always eat…and that’s where most people want to be. Sometimes we need to re-tune our hunger signals, we need to relearn what foods get us to where we want to be. Tracking energy intake and expenditure can help you get there.
Track to eventually not track!
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