| Let me show you how I know. Not with my opinion, but with a study. |
| Two researchers at Duke University collected 14 exercise studies covering 450 people and measured one thing: how much the exercise actually added to each person’s total daily calorie burn, compared to how much it should have added if the body simply stacked the workout on top of everything else. |
| They split the results by type of exercise: aerobic work like running, walking, and cycling in one group, and resistance training like lifting or bodyweight strength in the other. What came back was two completely different stories. |
| What they found |
| Duke University, 2026. Pontzer and Trexler, Current Biology. |
| The cardio exercisers (they kept about a third) |
| In the aerobic exercise groups, about 70 percent of the expected calorie burn from the workouts never showed up in total daily energy expenditure. The body compensated for it by pulling back on other processes. |
| The strength trainers (three groups, and they kept more) |
| Only three of the twenty one groups did resistance training, and in two of them compensation ran the other way. Their total daily burn came in above what the exercise alone predicted. All three trained at a lower dose than the cardio groups, so the authors treat this as a signal and not a settled result. |
| The type of exercise, not the effort, appeared to decide how much of the burn counted. |
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| In other words, the treadmill may promise 300 calories, but the body appears to add only about 90 to the daily total… and the researchers never found that the leftover burn turned into weight on the scale either way.
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| Her effort was never the variable. The exercise type was. And if you have been fighting the same treadmill, neither was yours. |
| Why would the body give back calories it just spent an hour earning? |
| When she adds an hour of cardio, the body does not stack those calories on top of everything else it was already spending. Studies suggest it pulls energy from other jobs: the resting burn dips, the burn while she sleeps dips further, and the small motions she makes all day without thinking, the pacing from room to room, the fidgeting at her desk, slow down. Some researchers read that last part as plain tiredness rather than biology, and either way it lands in the same place for her. The net addition from that treadmill session may be less than half what the screen promised. In the handful of strength groups, the resting burn trended the other way, higher than predicted, though three groups is not enough to call it settled. The worst combination the researchers found was the one she was told to do: hours of cardio paired with eating less. When both happened at once, compensation went higher still.
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| Laura never stood a chance. Neither did you, I’d bet. |
| That’s the part no one says out loud… |
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