Should You Eat Back Exercise Calories for Weight Loss?

During my 13 years writing for FutureDerm (!), I talked primarily about skincare. Since starting ResearchingEverything in November 2020, I wanted to talk about everything that interests me on the same level as skincare – namely, running, nutrition, personal development, business, and weight loss (at least until I hit my goal weight).

At the time of this writing, I’m 6 months postpartum, and I’m finally ready to lose 15 pounds I’ve been hanging onto for 10+ years. Like many people, I signed up at MyFitnessPal and started logging calories. I have had anorexia in the past, so I wanted to be careful and not go below the proper number of calories. That’s what led to the question: What is the proper number of minimum calories: before or after exercise?

1. It’s easy to overestimate calorie burn, as most apps and exercise equipment are 30-50% inaccurate. 

According to MyFitnessPal nutritionist Elle Penner MPH, RD, it’s not necessary to eat back the calories you burn through exercise. As she states, “The main reason is this: It’s easy, and fairly common to overestimate calorie burn (both from everyday activity and from exercise) and underestimate calorie consumption. By going out of your way to eat back every calorie you expend during exercise, you may unintentionally undermine your efforts to lose or maintain your weight.”

Other experts agree, like Legion Athletics’ Armistead Legge and Dr. Brian Grant: “The short answer is that no, you probably shouldn’t eat back the calories burned during exercise… Many of these devices are off by 50% or more (a fitness tracker might say you burned 300 calories during your walk, when you only burned 200 calories). Research also shows that most smartphone fitness tracking apps aren’t any better, and are often off by 30 to 50%.”

Of the devices, even ultra-popular Apple watches were found to overestimate energy burn by 40%. So if yours says you’ve burned 400 calories, you might actually only have burned 240 calories (Insider).

Your exercise equipment also isn’t a reliable indicator of how many calories you’ve burned through activity. For example, a study conducted by researchers at the University of California-San Francisco’s Human Performance center found that, on average:

  • Stationary bicycles overestimated by 7%
  • Stair-climbers overestimated by 12%
  • Treadmills overestimated by 13%
  • Elliptical machines overestimated by 42% 
You are often eating more or fewer calories than you think you are.

2. It’s also easy to undercalculate calories consumed, as most packaging and restaurant counts are inaccurate.

As if unreliable apps, wearable devices, and exercise equipment weren’t bad enough, it’s also hard to depend on restaurant calorie counts. According to a study from Tufts University, 53% of meals are at least 10 calories below what is stated, whereas 40% are 10 or more calories higher. What was most alarming was the significant fraction of foods tested that packed 100 or more extra calories. Typically, the foods that were stated as low-calorie on the menu contained more calories than they should. Also prone to higher-than-stated calorie counts were desserts and foods high in carbohydrates, like noodle- and rice-based dishes.

In the study, Tufts researchers measured the actual caloric energy in 269 foods from 42 restaurants, including seven fast-food and seven sit-down eateries, in three states. Among restaurants tested were such popular chains as McDonalds, Burger King, Olive Garden, Chipotle, Taco Bell, Boston Market, Bob Evans, P.F. Chang, and Dennys. Food items were ordered for take-out and then tested in a laboratory by measuring the heat produced from the foods combustion.

And if you think you’re exempt because you prepare most meals at home, you’re also wrong. According to VeryWellFit, calorie counts on packaging can be as misleading as 20% too few calories. For example, a Lean Cuisine shrimp and pasta dish stated a count of 250 calories; researchers found that it actually contained 319 calories, a difference of 28%. On the other hand, a South Beach Diet turkey meal had a lower calorie value than stated, 222 calories versus 212 actual measured calories.

Overall, however, study authors noted that the variations were statistically insignificant and there were positive and negative variations in all brands tested. That is, no brand was better than the others in providing accurate numbers.

Just another reason to not meticulously eat back calories for weight loss.

You could be eating back exercise calories twice.

3. Your activity calories are already counted towards your “Caloric Deficit.”

Any time you meet with a professional dietitian, or use a well-programmed app, they will ask you to define your activity level, whether that’s sedentary, lightly active, active, or athlete-level active.

So let’s say you tell My Fitness Pal that you’re ‘Lightly Active’ – it assumes that you’re already burning a certain number of calories per day.

If you then add in the ‘Exercise’ calories, these could already be accounted for in your ‘goal’, meaning that you are “eating back exercise calories” twice.

Let’s use me as the example:

If I set my ‘activity level’ to ‘Not Very Active’, MyFitnessPal gives me a goal of 1,200 calories.

If I set it to ‘Very Active’ I get a goal or 1,880 calories.

This is a HUGE difference (680 calories), so getting this wrong then following it religiously could really compromise you.

On days I run 8 miles, I’m probably burning somewhere between 700 and 900 calories. But, if I’m already set to “very active,” I don’t need 1880 calories plus adding in another 700 to 900 calories to continue to lose weight in a healthy manner. Instead, the calculation already has it built in.

4. Exercise accounts for less than 5% of your total daily caloric expenditure.

The most-commonly used calculation for how many calories you should eat each day is the Total Daily Energy Expenditure, or TDEE:


Your total daily energy expenditure (TDEE) is determined by four factors in the equation:

  • BMR = Your basal metabolic rate, which is the amount of energy you burn just by existing. This rate is determined by your height, your weight, your age, your sex, health (factors like hypothyroidism play a role), genetics, and your ratio of lean mass to body fat. This is 70% or slightly more of your TDEE.
  • NEAT = Non-exercise energy thermogenesis, which refers to calories you burn during non-structured physical activity. This can be anything from walking around the house to fidgeting throughout the day. People with more active and physical jobs tend to have higher NEAT. This is roughly 15-20% of TDEE.
  • TEF = Thermic effect of food, which is the amount of calories you burn by eating. Some diets make a big deal of this, citing the amount of energy your body utilizes to break down proteins and fibrous foods, like fruits and vegetables. However, like TEA, this tends to be small, like 10% or less of TDEE.
  • TEA = Thermic effect of activity, or exercise. This is what we are talking about when we say eating back “exercise calories.” This is typically 5% or less of TDEE, unless you’re, like, running a half-marathon or something.

The TDEE is the number you want to use to calculate how many calories per day to eat for weight loss. For instance, if you eat 500 calories below your TDEE daily, you should lose roughly one pound a week. If you eat 1000 calories below your TDEE daily, you should lose roughly two pounds a week. 

How It All Fits Together

If you calculate your TDEE, including your average workouts and activity level for a week or two, you can determine how many calories, on average, you want to eat each day in order to lose weight, without having to worry about “eating back calories.” So, for instance, let’s say your TDEE is 1800 (like mine). If you want to lose one pound per week, you should average 1300 calories per day.

Bottom Line

Turns out, sadly, you don’t need to eat back exercise calories for weight loss. If you do, you may find that you’re hindering your progress.

If some days you’re exercising hard, and MyFitnessPal says you need to eat 1600 calories and you don’t (i.e., it says you’re 300 calories “under”), it shouldn’t hinder your weight loss, slow your metabolism or put you into starvation mode. For one, you might not have burned as many calories as you think (typically 30-50% less than your exercise equipment or fitness trackers report). For another, because your food probably contains 10-20% more calories than the packaging and restaurant menus state. And, lastly, one day alone won’t do any damage. Your average over a relatively short amount of time is in the “moderate calorie deficit” zone –- one extra slice of pizza or 280-calorie Snickers bar in that week, and you’re right back to the average you need to be in.

That said, if you’re consistently under the recommended number of calories daily, and your weight loss progress stalls, try adding back 50-100 calories/day, and see if your results improve.

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