Clinical Report: Smartwatch Calorie Accuracy Assessed in Hispanic Adults
Overview
A study published in PLOS One evaluated the accuracy of smartwatch estimates of physical activity energy expenditure (PAEE) among Hispanic adults. Findings indicated significant device-dependent differences in PAEE accuracy and a correlation between higher body fat percentage and greater estimation errors.
Background
Accurate estimation of physical activity energy expenditure is crucial for effective health monitoring and intervention strategies. Smartwatches are increasingly used for this purpose, yet their accuracy can vary significantly based on device and user characteristics.
Data Highlights
| Device | Mean Bias (kcal) | Mean Absolute Percentage Error (%) |
|---|---|---|
| Apple Watch Series 8 | 22 | 36 |
| Garmin Forerunner 955 | 69 | 78 |
| Samsung Galaxy Watch 5 | 57 | 66 |
| Fitbit Sense 2 | 3 (129 with outliers) | 32 |
Key Findings
- Device-derived PAEE estimates varied significantly among the four smartwatches tested.
- Higher body fat percentage was linked to increased bias and error in PAEE estimates across devices.
- Fitbit produced implausible estimates exceeding 450% of the criterion value in some cases.
- No significant association was found between Fitzpatrick skin type and absolute percentage error.
- Mean bias for Fitbit increased to 129 kcal when outlier estimates were included.
- Device-specific differences in energy expenditure estimates were noted, with Garmin and Samsung showing higher overestimations compared to Apple.
Clinical Implications
Clinicians should be aware of the variability in smartwatch accuracy when interpreting physical activity data from patients.
Conclusion
The study highlights the importance of understanding device-specific limitations in smartwatch calorie expenditure estimates.
Related Resources & Content
- Kostrna J, et al., PLOS One, 2026 -- Body fat, skin tone, and the accuracy of smartwatch caloric expenditure estimates
- Frontiers in Digital Health, 2026 -- Evaluation of Energy Expenditure Estimates from Smartwatches During Outdoor Exercise Activities
- npj Digital Medicine, 2025 -- Evaluating the Precision of Apple Watch Metrics: An Ongoing Systematic Review and Meta-Analysis
- Frontiers in Digital Health, 2026 -- A Prototype Smartwatch for Monitoring Dynamic, Compound and Plyometric Exercises in Cancer Prehabilitation: A Development and Validation Study
- Role of Physical Activity in Obesity Treatment and Cardiometabolic Health: A Scientific Statement From the American Heart Association
- MDSpire News — Wearable Trackers: These Activity Metrics Drive Calorie Burn
- Wearable Trackers: These Activity Metrics Drive Calorie Burn
- Body fat, skin tone, and the accuracy of smartwatch caloric expenditure estimates | PLOS One
- Role of Physical Activity in Obesity Treatment and Cardiometabolic Health: A Scientific Statement From the American Heart Association
- The accuracy of Apple Watch measurements: a living systematic review and meta-analysis | npj Digital Medicine
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