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Should you eat back your calories from exercise?

Question - should I eat back the calories I've burned through exercise? (My goal is to lose weight)

The short answer is no as this will slow down your weight loss efforts.

The fundamental principle of weight loss is to create a calorie deficit, which necessitates two key elements: how much food you consume and how much energy you burn. We can measure the first part of this equation by tracking our food and if we can also measure how much we burn through activity, it should be straight forward to lose weight right?

In theory yes, however it's not quite that simple.

With FitBit's, Garmin and Apple watches now estimating calories burned through activity, MyFitnessPal is now able to pull through your calories burned and add them to your daily calorie target. So if you burned 500 calories during a workout and your calorie target was 1800, you will now see your new target of 2550. This is a good thing right?


While tracking calories burned during exercise can be helpful to see how active you are, trying to eat those calories back can actually sabotage your weight loss efforts.

Problem 1 - Your tracker isn't accurate

The major issue is that estimating calorie burn is incredibly difficult and acitivity trackers aren't right. A study in 2016 showed these trackers can overestimate acitivity calories by up to 40% . Another study showed how "none of the devices tested were in acceptable ranges to measure energy expenditure". These are not trivial amounts. If your apple watch estimated you burned 40% more than the 500 calories you actually burned in a workout. This would be 200 calories more. Over time these would add up and easily stall your weight loss efforts.

Problem 2 - Metabolic adaptation

Studies show that when you lose weight your metabolic rate comes down. This causes a drop to your Resting Metabolic Rate (RMR) as well as Active Energy Expenditure (AEF) or, how many calories you burn during exercise. This means that as you lose weight, the calorie burn from your tracker is getting less and less accurate.

Problem 3 - You get fitter

This one is a little more subtle. As you get fitter and better at exercise, calorie burn decreases when performing the same activity at the same intensity. This is due to the fact that you become more efficient and cost-effective, necessitating less energy to complete the task. This further adds to the inaccuracy of your fitness tracker.

Problem 4 - You're reducing your calorie deficit

By eating back the calories you've burned you're simply reducing your calorie deficit and slowing down weight loss. Worse, research suggests that after exercise, you're more likely to overcompensate by eating more calories than you've burned. How many times after a hard workout you think you deserve that ice cream???!

Word of warning - Use your common sense here. If you have exercised a lot more than normal you may need to eat more food. But rather than relying on your tracker, just use your hunger cues. If you're starving then eat, if not then don't.

Problem 5 - You've already accounted for these calories

When you figure out how many calories you need, you'll probably already have factored in the energy necessary for exercise. This means if you increase your calories via food or drink, you will be wiping out your deficit and perhaps exceeding it, resulting in weight gain.

What should you do instead?

1. Get your starting calories right. When it comes to setting your calorie intake, you have a choice: account for your activity and then create a deficit, or use exercise to make a deficit. For help with this, check out this post or then get in touch to see how we can help.


RMR Metabolism Testing

A resting metabolic rate test is one of the only true methods to accurately determine how many calories you are burning at rest.


2. Use exercise to increase your calorie deficit and not as an excuse to eat more! Research shows us that it's far easier to create a calorie deficit from eating less than exercising more. However, this does not mean you should stop exercising! We know the benefits of exercise extend far beyond just weight loss.

3. Be flexible - Rather than rigidly sticking to a set calorie number, use subjective measures like hunger and energy levels dictate whether you need to change what you're eating.

Do you need more help?

If you've tried everything to lose weight and still struggling, then try our Ignite - the weight loss programme that tests your metabolism to build a plan unique to you.

Find out more and sign up here.

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