Why you shouldn’t eat back your exercise calories…. 🏃🏼♀️
Many of us use activity trackers / fitness watches; they’re fab tools to monitor activity and motivate us to get fitter, but they can also cause some issues.
The main issue is the figure they provide for calories burned, particularly when linked to food logging apps. Apps like myfitnesspal give you a daily calorie target or budget to spend, based on your current stats, goals and activity levels. If you have a tracker linked then it automatically adds any calories burned to this figure e.g if your goal is 1700 cals and you burn 500 cals in spin it gives you 2200 cals to ‘spend’ (eat).
Great! So you can eat more right? Wrong! You shouldn’t be eating back those exercise calories. Aside from the fact that you have already accounted for your activity level in the daily calorie goal, the main issue is that the tracker is overestimating calories burned. Recent studies found that, despite being pretty accurate for heart rate readings, devices overestimated calories burned by 27 – 93% ! If we assume a 40% error rate you can see on the graph how much it overestimates (blue is actual burn, red is the tracker reading) e.g. a long walk burns 1500 cals on the tracker, but if you ate those back you’re actually over eating by 300 and 1450 cals!
This is why if you’re eating back those exercise calories you could easily wipe out the calorie deficit. Best-case, it slows progress, worst-case you overeat and put on weight. Also, as you get leaner and fitter the calories burnt in general activity and exercise decreases, so you’re burning even fewer calories than the device is reporting.
That’s not to say you shouldn’t record workouts and steps; it’s a great way to look at your relative effort and fitness. Use them as a way to encourage more activity but not as a reason to eat more. In the paid version of myfitnesspal you can choose not to add those extra calories, or simply un-link your tracker so it no longer gets that info.
So if you workout as a way to increase your calorie expenditure, that’s fine, just don’t eat back those calories, as it defeats the entire point of increasing activity in the first place.