What I Learned From Tracking Calorie Burn Throughout the Year
It’s been over a year since I started using MacroFactor, an app that calculates my TDEE (Total Daily Energy Expenditure) in real time. It’s a paid app, but as we noticed when it came out , there are free tools out there that do the same calculations. And whichever method you use to track your TDEE, the results can be instructive. I, of course, thought so.
What is TDE?
Before I get to what I’ve learned, here’s a quick reminder of TDEE. As the name suggests, this is a record of your total daily energy expenditure or calorie burn. This includes the calories you burn while exercising, the calories you burn walking and fidgeting, and the calories your body burns just to keep the lights on, so to speak – to activate neurons in your brain, to pump blood. and everything is so good.
People often estimate their TDEE using a formula like this one from tdeecalculator.net. When I enter my height, weight, age, gender, and activity level into this site, I get an estimate of 2090 calories per day. Spoiler: Everyone is different, and this rough estimate falls far short of the number I get using a more accurate method.
Some people try to better understand their TDEE by plugging in their numbers as if they weren’t doing structured exercise and then adding their fitness trackers for their workouts to their calorie burn reports. So let’s say the calculator thinks you burn 1,700 calories just by being, and then you run five miles and record another 500 calories burned. It will be 2200 per day. But exercise doesn’t burn as many calories as you think , so your numbers are likely to be wrong.
Why does your TDEE matter?
If you eat more than your TDEE, you will gain weight. If you eat less than your TDEE, you will lose weight. This is the whole idea behind the concept of a calorie deficit or surplus . (If you’re eating the same amount as your TDEE, your weight should stay the same.) There are a lot of caveats to this process, but that’s the model we’re working with.
The MacroFactor app and the spreadsheets that preceded it ask you to track your calorie intake and your weight. So I’ll grab some enchiladas and list them on the app (480 calories). Later I will eat a banana (105 calories) and so on. By the end of the day, I will have the total number of calories I have eaten.
Meanwhile, I also weigh myself every day, or at least most days. The application or spreadsheet just links them. If I’m losing about a pound a week, I’m probably burning about 500 more calories a day than I’m eating. This means that if I consume an average of 2000 calories, my TDEE should be 2500. If my weight remains stable, then the amount I eat should be equal to my TDEE.
TDEE calculations are based on the model
People often repeat the phrase “calories in, calories out” as if it’s as reliable as the laws of thermodynamics. But it doesn’t really work that way. The numbers we have are calories taken from food packages and databases, and we can only estimate calories burned from any of a variety of sources. Energy can neither be created nor destroyed in the universe, it is true, but the way we measure food and exercise does not represent a strict accounting of energy in the physical sense. (As two biochemists once quipped , to expect different metabolic processes to produce the same energy output would be a real violation of thermodynamics.)
For example: how many calories your body can actually extract from food depends on the type of food and factors such as gut microbes, which vary from person to person and maybe even from day to day in the same person. Our food labels cannot accurately reflect all of this.
Similarly, the number of calories we get from a given food is also a rough estimate. If I eat a banana, I will log it as the same food every day (“banana, medium, 7 to 7-7/8 inches long”) and thus get the same 105 calories in my food log everyday. But some of these bananas will be smaller or larger than others, and they will release more sugar as they ripen. Not all of them will contain exactly 105 calories.
There are also many uncertainties when it comes to burning calories. You become more efficient at running (burning fewer calories per mile at the same pace) when you run better. Even if you measure calories burned with TDEE based on your weight, there are other factors that can change your weight besides whether you’re burning fat or gaining it. If you have eaten salty foods, your weight will increase the next morning. If you drink a few beers, you might get a little dehydrated and you’ll see the bar go down. This may change your calculated TDEE, but it won’t change the number of calories your body actually burns.
The idea that our imprecise measure of “calories in” mathematically balances our imprecise measure of “calories in” is hardly a fundamental truth of the universe; it’s a model that we simply declare to be true and then analyze the numbers and see what we can learn from those assumptions. Or, as scientists like to say, all models are wrong. Some models are useful . And this one was very helpful to me.
My real TDEE is very different from calculators.
Let’s go back to the estimate I mentioned on tdeecalculator.net. He thinks I’m probably burning 2090 calories a day. Well, according to MacroFactor, my expenses ranged from 2383 (when I started using it), to 2179 (when I had COVID and missed every workout for a week), to 2516 (a few days ago).
Even with the above caveats, this information is useful. I know that if I want to gain weight to ensure muscle growth, I need to eat foods that add up to more than 2516 calories per day on average. (Fortunately, the app does the math for me, recommending a specific calorie goal based on my current TDEE and the rate of weight gain or loss I want to achieve.)
Exercise doesn’t increase TDEE as much as you think
Has my exercise changed since I took notes? Yes, but not always in the direction my TDEE would point. Last winter, I rode a stationary bike almost every day and did shorter strength workouts in between hard days. Lately, I just do hard workouts and go for a daily morning walk. My TDEE is now 100-200 calories higher than it was when I continued with the Peloton series of applications.
This isn’t surprising given what we know about metabolism: exercise can temporarily increase your calorie intake, but your body tends to adjust to save energy elsewhere when you spend a lot on exercise. An active person may still have a higher TDEE than a less active person, but not as much as one might expect.
For the same reason, it doesn’t make sense to keep track of the calories you burn in every workout. I don’t track most of my workouts, so unfortunately I can’t go back and compare scores. But I feel more confident than ever in saying that the number on your fitness watch does not represent the number of calories you actually added to your total burn that day .
Eating more food increases TDEE
If my calories burned don’t increase much with more exercise, what is causing these spikes and dips on the chart? The most noticeable difference is how much I eat.
It may seem counterintuitive, but the more I eat, the higher the calorie burn. This may be because my body has more fuel, so it spends more on activities and metabolic processes that might otherwise be over budget. On the other hand, when I am eating in deficit, the budget can be a little tighter.
But this is not the only possible explanation. Remember that the TDEE model assumes that your TDEE is a single number, which it derives from your consumption and your weight change. I’ve always preferred to think of maintenance as a range . For me, that could be anywhere from 2350 to 2550 calories. If I wanted to lose weight, I would need to drop calories below the lower end of this range and the app would process the numbers and report 2350 as my “true” TDEE. If I wanted to gain weight, I would have to go above the upper limit of this range, and a higher number would be my true TDEE.
It’s kind of an intuitional hypothesis, but it’s consistent with my observations: whatever the explanation, I can “increase” my TDEE by a couple of hundred calories just by switching from a weight loss diet to a mass gain diet.
Muscle mass increases TDEE
It’s harder to track from month to month as muscle growth is quite slow, but if I look back further than last year, I can say there’s been a big jump in how many calories my body uses at a similar level of activity. I used to lose 1800 calories a day of weight and managed to gain weight for 20 to 2000 years. Last year, before I started using MacroFactor, I was gaining about 2700-2800 calories per day.
Now my maintenance cost is 2500. If I want to lose weight, I need to reduce my intake to about 2100 calories per day. To gain, I need to eat about 3000.
Why? Well, we know that lean body mass (including but not limited to muscle) affects our metabolism. You can read more about this here . In short, the bigger you are and the more lean tissue you have, the higher your metabolism. Surprisingly, age doesn’t matter much at all when these two factors are taken into account.
If I look back at the workouts I did years ago when my TDEE was at the lows of the 2000s, I was a smaller person – maybe 15 pounds lighter – with a lot less muscle. I’m not saying the whole difference is in the muscles, but it’s probably a big one. And since I wasn’t as strong, I worked with lighter weights. My working weight for a squat set is probably 50 pounds more now than it was back then; this will add up when it comes to my overall calorie burn.