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Why you shouldn’t eat back calories burned during exercise

Are you among the millions of people who use an activity tracker daily, especially when exercising? If you’re using a smart watch tracker or something like MyFitnessPal it might seem like perfect sense to eat back the calories that you burn. As a huge foodie myself I wish it were that simple. I would love an excuse to indulge after a tough training session!

However it’s a much better decision not to adjust your calorie intake around exercise if your goal is to lose bodyweight or body fat. There are plenty of reasons to avoid compensating, which we will go through below, but firstly I want you to think about the simple fact that MyFitnessPal doesn’t count resistance training as calorie burning exercise. Strange huh?

Understanding the initial science

For us to fully understand this topic it is important that we understand how to estimate our daily calorie intake. This is made up of a combination of four things: basal metabolic rate (BMR), non-exercise activity thermogenesis (NEAT), the thermic effect of food (TEF) and exercise based activity thermogenesis (EAT).

BMR: this is the amount of calories it takes for us to simply exist. Without any movement involved, this amount of food keeps us ticking over and allows our organs to function in the way that they need to.

NEAT: this is this amount of calories burned whilst moving outside of structured exercise sessions. These calories can be burned through walking up the stairs, moving around the kitchen whilst cooking or just scratching your head.

TEF: this describes the calories used by the body when eating and digesting food. This usually makes up the smallest calorie burn of these 4 but it’s worth noting at this point that of the 3 main macronutrients, protein (by a small amount) burns the highest number of calories when being ingested.

EAT: this represents the calories burned during structured exercise and is going to be the main topic of this blog.

Why you shouldn’t eat back exercise calories

Weight loss and fat loss occur when you CONSISTENTLY consume lower calories than you burn and although exercise has its many benefits (including disease prevention, improved socialisation and mental health), this is mainly achieved through diet manipulation. Let’s have a look at the main reasons for why you shouldn’t eat back your calories:

1. Your activity tracker is probably wrong.

By this I don’t mean your food calorie tracker, those are usually pretty good. However, studies have consistently shown that activity trackers on phones, Apple watches or fitbit’s overestimate calorie expenditure. Shcherbina. A, et al. 2017 demonstrated that after testing 7 popular wrist-worn devices, none of them achieved less than 20% error when estimating energy expenditure. Some even achieved a staggering 92% error. This is obviously a major problem for anyone who considers eating back calories after activity because it will be impossible for anyone to know their devices error percentage at any given point.

Let’s do some maths. Your watch could tell you that you burnt 480 calories during a workout, which could actually turn out to be 400 calories (if you get lucky and only get a 20% error). If you get unlucky and have an error of 90%, you could have only actually burned 250 calories. These extra calories, added up across the space of a week can create quite an issue for anyone monitoring their intake of food for a body composition based goal and could make or break your progress.

2. Your daily calorie target may already include exercise calories.

Now that you have read this and understand the points made at the beginning where we looked at what makes up our daily calorie expenditure, you will remember us including EAT – the calories burned from structured exercise. The majority of calorie calculators on smart devices will take into account an estimated activity level so you do not need to take it into your own hands as this will lead to overcompensation.

Now that we have covered a few of my go-to strength exercises, I’d like to turn our attention to plyometrics. This exercise category represents movements which use rapid and repeated stretching and contracting of muscles. You’ll no doubt have seen or heard of these before but there is much more to these than people usually talk about. As mentioned above, these will help with our running economy by improving force transfer and allowing us to reduce ground contact time whilst moving.

What should you be doing instead?

Now that you hopefully understand how much of a minefield trying to eat back your calories can be, let’s can discuss your best options. My recommendations are to use food trackers to monitor calorie intake and to use activity trackers to monitor step counts (as these can be much more accurate than anything else) and distance (when running), but nothing else. Trust that your calorie calculation or coach has included exercise calories in your daily intake and use your training sessions for their other benefits because in reality exercise sucks for weight loss. By this I mean that if you consumed a maintenance level of calories and exercised in an attempt to lose weight you’d have great difficulty. You’ll be ten times better off if you use your diet to manipulate your bodyweight and use exercise for its benefits such as injury prevention, disease prevention, improved mental health and improved levels of sleep.

Thanks for reading


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