Wearables

Your watch's calorie burn is a guess. Often a big one.

Estimates, not measurements

Wrist devices infer burn from heart rate and motion. Studies have found errors that can reach tens of percent — brilliant sensors, rough maths.

Eating back ghost calories

Trust an inflated burn number and you'll 'earn back' food your body never actually spent. The maths quietly cancels your deficit.

The output check

You don't need a perfect burn number. You need to know if your composition is moving. That's an outcome, not an estimate of an estimate.

Use the watch for effort

Heart rate, strain and consistency are what wrist data does well. Let it coach effort — let a composition trend judge results.

Screenshot: trust map

Watch: effort ✓ heart rate ✓ consistency ✓. Trend: composition ✓ waist ✓ strength ✓. Calorie burn: a rough guide, never a budget.