Decision 9 of 10

Why your steps and workouts do not change your calorie target

Snapkin reads your steps and your active energy and shows them under the day. It does not add them to what you may eat. Most calorie trackers do the opposite, and this is the most requested thing we have decided against.

Written and maintained by Mattias Geniar. Last updated .

What the app does
Shows your activity, never adds it to your budget. Your calorie target is what you set, and a 15 km Sunday does not raise it on its own.
How much we believe it
One living review, and its energy section is 8 studies and 270 people. The direction is consistent. Nobody has measured the size of the error precisely.

What the review found

Lambe et al. (2026), a living systematic review and meta-analysis in npj Digital Medicine, pooled 82 studies covering 430,052 participants across 14 Apple Watch metrics. On energy expenditure it is blunt. Margins of error “were often large, both during exercise and at rest”. All six studies that calculated MAPE reported values of 20% or higher in at least one test condition. There was no clear pattern by exercise intensity, so you cannot even correct for it in one direction.

The same watch, measuring two different things Mean absolute percentage error. Lower is better; the range is across test conditions.
Energy expenditure, across conditions 9.71–151.66%

Best case running, worst case walking. All six studies reporting MAPE went above 20% somewhere

Heart rate during exercise under 10%

10 of 11 studies came in under 10%

Resting heart rate 1.69–7.2%

The sensor underneath is not the problem

0 160% error
The watch is good at measuring your heart and bad at converting that into calories. Only the second claim matters if a number is going to decide what you are allowed to eat. A walking error of 151.66% on a 400 kcal estimate is 600 kcal of extra food a tracker would have allowed you without saying so. Over a week, that is your whole deficit.
400 kcal a plausible estimate for an hour's walk What a tracker would show you
±600 kcal what a 151.66% error on it means Added to your allowance, without a warning
Every day that the estimate is too high, you eat the difference Not a rounding problem. Over a week it is the whole deficit

The evidence against, and the limits of what we are relying on

This is one review, and its energy-expenditure section is small. Only 8 of the 82 studies tested energy expenditure, with 270 people in total, 63% male, and the review notes that participants were “predominantly young physically active adults”. Five of those eight tested an Apple Watch Series 2 or older. Newer hardware and newer models may well be better, and this review cannot tell you that they are not.

It is also Apple Watch only. We apply the same rule to Health Connect, which collects data from Fitbit, Garmin, Samsung and others, and we have not read a comparable review for those. The evidence points the same way consistently enough that we would be surprised if they were different, but that is a judgement rather than a citation.

And there is a real cost to our choice. Somebody who really does run 15 km on a Sunday gets a target that ignores it, and they will have to raise their own goal. We think a plain number you adjust on purpose beats a flattering one worked out from an estimate that can be wrong by half. But people who train seriously have a fair complaint here.

There is a second argument we find convincing and are not citing, because we have not read the original studies. It says the body partly makes up for exercise by burning less elsewhere. If so, even a perfectly measured workout does not raise your total daily burn by the same amount. If that holds, it strengthens the case above. We will add it here properly, with numbers, when we have read the studies rather than summaries of them.