Popular Smartwatches Overstated Calorie Burn in Study
Researchers found that four common wearable devices overestimated calories burned during workouts by up to 25%.
Updated on Sept. 21, 2026 in Nutrition
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A Florida International University study comparing four popular smartwatches to clinical metabolic analyzers found that all tested devices produced inaccurate calorie burn estimates. The findings highlight significant limitations for users relying on these wearables to track exercise energy expenditure.
Why it matters
Understanding the limitations of wearable health data is crucial for anyone using these devices to manage daily calorie intake or exercise goals. The study suggests that consumers should view these digital estimates as general approximations rather than precise clinical metrics.
In a controlled study of 58 adults using a recumbent bike, researchers evaluated the Apple Watch Series 8, Fitbit Sense 2, Samsung Galaxy Watch 5, and Garmin Forerunner 955. Every device tested overestimated energy expenditure compared to the gold-standard COSMED K5 metabolic analyzer.
The players
Florida International University
The public research institution in Florida that led the investigation into the clinical accuracy of consumer wearable technology.
Apple
A technology corporation that manufactures the Apple Watch series, which was included in the study as the most accurate of the four tested devices.
Fitbit
A subsidiary of Google that produces wearable fitness trackers, including the Sense 2 model assessed for its tracking reliability.
Samsung
A consumer electronics company that manufactures the Galaxy Watch line of wearables used for health and fitness monitoring.
Garmin
A global technology company specializing in GPS-enabled wearable devices designed for athletic training and fitness tracking.
The details
The devices use internal algorithms to estimate energy expenditure by tracking heart rate and movement patterns, which struggled to keep pace with the alternating intensities of the study workouts. While the Apple Watch performed with the highest accuracy among the group, other models from Garmin and Samsung produced larger overestimations, and some Fitbit readings failed entirely or provided implausibly low data points.
Timeline
September 21, 2026: The study results were published.
Health Landscape
The COSMED K5 metabolic analyzer serves as the clinical benchmark for evaluating the accuracy of energy expenditure measurements. This study marks a necessary check on consumer-grade tracking, which often assumes a level of precision that real-world performance does not support.
If you rely on your watch to guide your nutritional intake, treat the calorie numbers as loose estimates rather than hard targets. It is worth discussing with your doctor how to best track your physical activity and energy needs if you are managing a specific health condition.
The takeaway
Smartwatch calorie data can be off by up to 25%, making these numbers better suited for tracking trends than for exact metabolic accounting. Focus on relative changes in your activity level rather than the specific calorie totals displayed on your wrist.
Further reading
Learn more about managing your fitness goals in our Nutrition section.
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Do you trust your fitness tracker to provide accurate calorie burn information for your health goals?
