An hour of cardio and 600 kcal (calories) gone? A 2026 review in Current Biology suggests the real effect is smaller.
Short answer: You burn less than the watch says. In a review of 18 aerobic trials (Pontzer and Trexler, Current Biology 2026), the body made up for a large share of the calories burned in cardio, on average. If the watch shows 600 kcal, your day's total burn rises by less than that.
What the 18 trials found
Pontzer and Trexler went through 18 aerobic interventions in Current Biology (2026).
The body makes up a large share of the calories "burned in cardio" somewhere else. Researchers are still working out exactly how. Likely routes include a lower resting metabolism and less movement outside the session. The watch shows 600 kcal? In reality the day's expenditure rises by less.
When does this hurt most? Compensation tends to be larger in a deep deficit and with long, regular training.
Strength training is where the data get thin. We have far less data for lifting, so we do not know how much the body compensates. What we do know: lifting helps you keep muscle in a deficit. The minimum effective version is in strength training: one hour a week.
Cardio is good for your heart, your head and your fitness. As the main fat loss tool, it is weak.
The order does not change. Food is on top: a calorie deficit. In 13 years of coaching I have not seen a shortcut. Then strength training, which keeps muscle. Cardio comes on top, as a bonus. Walking is easier to keep up day after day, and for many of my clients it fits better than long cardio sessions. More in how many steps a day. Losing fat with little formal exercise is in lose weight without exercise. Whether the cardio is fasted does not rescue the arithmetic: fasted cardio.
If fat loss is built on the treadmill, it may be built on the wrong lever. The question I would rather ask: when did you last log a full day with no exceptions, including the square of chocolate, the two spoons of oil and the taste of sauce?
If tracking makes you anxious or food takes over your thoughts, talk to your doctor before counting anything.
Frequently asked questions
How does the body claw back calories burned in cardio?
Researchers are still working out exactly how. Likely routes include a lower resting metabolism and less movement outside the session.
When is the compensation after cardio largest?
It tends to be larger in a deep deficit and with long, regular training.
Does the same thing happen with strength training?
We do not know yet. There is much less data for lifting than for cardio. Its main job in a deficit is keeping muscle.
Is cardio useless for fat loss?
Cardio is good for the heart, the head and fitness. As the main fat loss tool it is weak.
What should I focus on instead of cardio?
Food first: a calorie deficit. Then strength training, which keeps muscle. Take cardio as a bonus on top.
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Apply for coaching Get the free Fat Loss KitSources, so you can check:
1) Pontzer and Trexler (2026), Current Biology. DOI: 10.1016/j.cub.2026.01.025. Review of 18 aerobic interventions: the body compensates for part of the calories burned in cardio
Martin Barna
Online nutrition and fitness coach. Since 2013 I have coached 600+ people through fat loss.
Apply for coachingThis article is for information only. It is not medical advice. If you have a health condition, talk to your doctor.