We are currently running nutrition challenge. This involves tracking consumption and expenditure of calories using our apps and devices. But how accurate are these calculations and should you use them when deciding on your nutrition choices that day?
How accurate are calorie calculations?
When we calorie count, we are generally using two elements to establish our calories burned.
Basal Metabolic Rate (BMR) – This is the number of calories we burn at complete rest.
Total Daily Energy Expenditure (TDEE) – This is how many calories we burn in a regular day.
If we look at this first. There are more than 6 different formulas to calculate this. All of them use height, weight, age and gender and some also incorporate body fat to calculate more closely. The formulas that use bodyfat already have some accuracy problems because bodyfat calculations using readings from household scales can be widely inaccurate thus skewing these calculations. That aside an experiment was carried out to test the accuracy of BMR and found that people with identical BMR could have a variation of 20% in either direction. Meaning that two people of the same gender, height, weight and bodyfat could have 800 calories in difference in their metabolism.
Usually this is simply our BMR multiplied by a number that based on how active our regular day is. E.g. BMR 1.2 for a fairly sedentary office worker, 1.5 for someone with an active job (builders, tradesmen etc.). If we look at the inaccuracies of BMR and then look at how generally TDEE is calculated, we can already begin to see several flaws in the system.
For those who wear devices such as Fitbit, Apple watch, Garmin or the like, these trackers use much of the data above and then an algorithm that includes the data points it collects such as steps, heart rate and any other data the device can obtain to calculate calories burned. Apps such as MyFitnessPal use a similar system solely using activity type and duration. All of these methods will have limited accuracy.
We also have to realise that our calories consumed numbers will also be inaccurate. Food labelling is based on an average worked out via ingredient and our portion measuring will not always be possible and even when it is it probably isn’t perfect!
Why bother tracking if there’s no accuracy?
You may have read above and thought to yourself if Jeremy is telling me all of this isn’t accurate then what’s the point? Well the reality is for what we need the data for we don’t have to have scientifically accurate results. What we need are consistent results for us. Calculating BMR and TDEE for yourself will give you a rough number to base your calories around. Using activity trackers to give even more calorie data will give you a daily calorie expenditure number. Using MyFitnessPal to track calories consumed will give us a daily calorie intake number. If we exercise more then we’ll see our daily expenditure go up and if we eat less, then our calorie intake will go down. What’s important is to combine these two numbers with our body composition data.
Body Composition Data
Now bodyfat scales may not give your actual exact bodyfat percentage but if you lose or gain bodyfat it will show you the change. (Make sure you measure the trend as the scales will give some anomaly results.) It’s the change in bodyfat that really matters. If you are losing bodyfat then you’re doing something right. Just don’t worry about trying to hit a certain percentage as this is where the inaccuracy comes into play. Use the change in bodyfat, your body circumference measurements, the fit of your clothes and progress photos as a way to gauge progress.
How to use the data
Once we realise the data isn’t scientifically accurate, we just need to use the consistent data differently.
We start of by using the guide number of calories that MyFitnessPal calculates for us.
Your app shows:
Average Daily Calorie Consumption: 1800kCal
Average Daily Energy Expenditure: 2100kCal
Daily Calorie Deficit:300kCal
You would expect to be losing bodyfat and weight. However, if you aren’t seeing any change this doesn’t mean you are some kind of scientific wonder it just means that you need to create a bigger ‘deficit’. Remember that we’ve established that the numbers calculated aren’t accurate so if you create a 600kCal deficit on paper it may well not be that in reality. With all body composition changes the priority on creating the deficit has to come from nutrition. The saying ‘You can’t out-train a bad diet’ is true.
IF we weren’t getting results what we’d look to create is the following numbers
Average Daily Calorie Consumption: 1500kCal
Average Daily Energy Expenditure: 2100kCal
Daily Calorie Deficit:600kCal
What we are doing is using the numbers to formulate the tipping point for when we start to create an ACTUAL calorie deficit.
The same principle would of course be for those of you looking to gain weight. People that are hard gainers (struggle to gain weight) will be amazed at the calories they need to consume to get where they need to be.
Everyone is different
The key point to remember is that everyone has a different metabolism. Apps and activity trackers are based on an average and this doesn’t apply to everyone. That doesn’t mean the data is useless, what it means is that you need to find the way to use it to get you results.
Fat loss and muscle tone isn’t just calories
I need to add this to the end of the blog because although calories play a part in changing body composition, they are not the only element of your diet and nutrition that will bring results. Over the next few blogs, I’ll talk about other key factors that you’ll need to think about if you want real change.