Should You Eat Back the Calories You Burn Exercising?
For most people trying to lose fat, no, or only a small part of them. Exercise calorie figures from watches, apps and gym machines are estimates, and they tend to run high. Food logs tend to run low. Eat back the full exercise figure and the two errors meet in the middle, often wiping out the deficit you thought you had. A safer rule: set your daily target to include your usual training, and treat the exercise readout as a measure of effort, not a food allowance. The exceptions are people training very hard or for long durations, and people trying to maintain or gain weight, where eating some back is sensible.
Why apps tell you to eat them back
Many food logging apps work in two steps. They set a daily calorie target based on your size and a sedentary or lightly active lifestyle. Then, when you log a workout or sync a watch, they add those exercise calories to your allowance for the day. On paper, that keeps your deficit the same whatever you do. In practice, it depends entirely on the exercise figure being accurate. It usually isn’t.
How wrong can the estimates be?
Watches estimate energy use mainly from heart rate and movement, combined with your age, height and weight. Gym machines use formulas based on speed, power or resistance. Both rely on averages that may not fit you. Heart rate in particular is affected by heat, caffeine, stress and poor sleep, none of which change how many calories you actually burned.
Independent tests of wrist devices have generally found heart rate reasonably accurate and calorie estimates much less so. The error varies by device, by person and by activity. Strength training is particularly hard for them, because heart rate stays raised during rests even though you are burning little.
There is also a subtler issue. The figure shown is often your total burn during the session, including what you would have used sitting on the sofa anyway. Only the extra counts. For an hour-long session, that resting share alone can be a noticeable chunk of the number.
Our post on why air bike calorie numbers disagree shows how different machines and devices can give very different readings for the same effort.
The other side of the error: food
Most people under-record what they eat. Not from dishonesty, but because cooking oil, sauces, drinks, tastes while cooking and second helpings are easy to miss or underestimate. A logged day that looks like a solid deficit can be near maintenance in reality.
So if the exercise number is inflated and the food number is deflated, adding the exercise calories back to your allowance pushes you towards eating more than you burn. That is the usual story behind “I train five times a week, eat back my exercise and I’m not losing anything”.
A simple approach that works
This is the method I use with most clients who want to lose fat:
- Set your target with training already included. Estimate your maintenance using your typical week, including your usual sessions. Our guide on working out maintenance calories covers the method.
- Take a moderate deficit from that. Not a drastic one. The aim is a target you can keep on training days and rest days alike.
- Eat roughly the same every day. Or slightly more on hard training days and slightly less on rest days, but with the weekly total the same.
- Ignore the watch figure for food purposes. Use it to compare sessions with each other, not to justify a pudding.
- Check against reality. After three or four weeks, look at your average weekly weight and how your clothes fit. If progress is steady, carry on. If not, adjust intake slightly.
The final step is what makes this work. The scale trend over several weeks is a far better measure of your real energy balance than any device.
When eating some back does make sense
There are real situations where ignoring exercise calories is a mistake.
| Situation | What to do |
|---|---|
| Long endurance sessions (long runs, rides, hikes) | Eat back a portion, perhaps half, especially after sessions of more than an hour or so. Under-fuelling hurts recovery. |
| Maintaining weight while training hard | Match intake to your real activity, adjusting based on weekly weight. |
| Trying to build muscle | You need a small surplus. Unfuelled training makes that harder. |
| Feeling exhausted, sleeping badly, training getting worse | Your deficit may be too big. Eat more on hard days. |
| An occasional much bigger day than usual | Eat a little more that day. Do not add the full estimate. |
Exercise still matters for fat loss
None of this means exercise is pointless for weight management. It means calorie burn is not the main reason to do it. Strength training helps you keep and build muscle while you lose fat, which changes your shape more than the scales suggest. Regular activity improves heart health, mood, sleep and appetite control. The UK Chief Medical Officers’ physical activity guidelines set out the benefits and recommended amounts.
In practice, diet creates most of the deficit and training decides what the weight you lose is made of: mostly fat, or fat plus muscle you would rather keep.
How we handle it in the studio
When I set a client’s nutrition target, I build in their sessions with me and their usual walking and activity. We then check the InBody results and weekly weight together. If fat is coming off and muscle is holding, the numbers are right whatever any watch says. If not, we adjust. In private 1-1 sessions in Highgate the focus is strength, with short conditioning blocks on the air bike, so the training protects muscle while the food plan does the fat loss work.
Check with your GP first if you have diabetes, a heart condition, a history of disordered eating, or are pregnant, before changing how much you eat around exercise.
Questions we get asked
Should I eat back calories from walking?
Usually not. Build your normal daily walking into your target. Only a much bigger day than usual, such as a long hike, justifies eating a little more.
Is my Apple Watch or Garmin calorie count accurate?
Calorie estimates from any wrist device are approximate. They are more useful for comparing your own sessions than for calculating food.
Why am I not losing weight even though I exercise a lot?
The most common reasons are eating back inflated exercise calories, under-recording food, and moving less outside training. A few weeks of careful tracking usually shows which.
Should I eat more on training days?
Slightly more on hard training days can help performance and recovery, as long as the weekly total stays where it should.
Read more about personal training with Artem in Highgate, or start at the homepage.
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