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Study finds smartwatches significantly undercount calories, especially for higher body fat

Florida International University research shows popular fitness trackers have substantial measurement errors that worsen with body composition.

newest coverage 1d agosummary written 1d ago9 pieces MastodonNewswiresGoogle News

What to know

  • All four tested smartwatch models (Apple Watch Series 8, Garmin Forerunner 955, Samsung Galaxy Watch5, Fitbit Sense 2) showed substantial errors measuring calories burned during exercise.
  • Measurement errors increased significantly as wearers' body fat percentage rose, indicating the devices cannot accurately adjust for body composition differences.
  • Smartwatches rely on heart rate and movement sensors combined with user demographic data but cannot directly measure caloric expenditure, making predictions vulnerable to individual physiological variations.
  • Study of 58 Hispanic adults with varying body fat and skin tones used metabolic analysis—the gold standard in exercise science—to validate watch measurements.

“Heart rate and movement are relatively accessible signals for a wrist-worn device, but caloric expenditure is much more complex.”

Jason Kostrna, Study lead, exercise scientist · The Conversation US ↗ · Sep 20

Jason Kostrna Study lead, exercise scientistFlorida International University Medical Photonics Laboratory Research institution

Study finds smartwatches significantly undercount calories, especially for higher body fat
The Conversation US

How it unfolded 2 developments, newest first · click a bar or a number to jump articlesposts

Peak 5 pieces in one hour at Sep 22, 3 AM; 9 pieces over 3 days (8 articles · 1 post) Sep 21, 7 AM — 2 pieces · 1 article · 1 post — Mastodon 1, Newswires 1Sep 21, 8 AM — quietSep 21, 9 AM — quietSep 21, 10 AM — quietSep 21, 11 AM — quietSep 21, 12 PM — quietSep 21, 1 PM — quietSep 21, 2 PM — quietSep 21, 3 PM — quietSep 21, 4 PM — quietSep 21, 5 PM — quietSep 21, 6 PM — quietSep 21, 7 PM — quietSep 21, 8 PM — quietSep 21, 9 PM — quietSep 21, 10 PM — quietSep 21, 11 PM — quietSep 22, 12 AM — quietSep 22, 1 AM — quietSep 22, 2 AM — quietSep 22, 3 AM — 5 pieces · 5 articles — Google News 4, Newswires 1Sep 22, 4 AM — quietSep 22, 5 AM — quietSep 22, 6 AM — quietSep 22, 7 AM — quietSep 22, 8 AM — quietSep 22, 9 AM — 1 piece · 1 article — Newswires 1Sep 22, 10 AM — quietSep 22, 11 AM — quietSep 22, 12 PM — quietSep 22, 1 PM — 1 piece · 1 article — Newswires 1Sep 22, 2 PM — quietSep 22, 3 PM — quietSep 22, 4 PM — quietSep 22, 5 PM — quietSep 22, 6 PM — quietSep 22, 7 PM — quietSep 22, 8 PM — quietSep 22, 9 PM — quietSep 22, 10 PM — quietSep 22, 11 PM — quietYesterday, 12 AM — quietYesterday, 1 AM — quietYesterday, 2 AM — quietYesterday, 3 AM — quietYesterday, 4 AM — quietYesterday, 5 AM — quietYesterday, 6 AM — quietYesterday, 7 AM — quietYesterday, 8 AM — quietYesterday, 9 AM — quietYesterday, 10 AM — quietYesterday, 11 AM — quietYesterday, 12 PM — quietYesterday, 1 PM — quietYesterday, 2 PM — quietYesterday, 3 PM — quietYesterday, 4 PM — quietYesterday, 5 PM — quietYesterday, 6 PM — quietYesterday, 7 PM — quietYesterday, 8 PM — quietYesterday, 9 PM — quietYesterday, 10 PM — quietYesterday, 11 PM — quiet 12
Sep 22yesterdaynow · 12:59 AM ET
  1. 2

    NPR and major outlets cover study findings

    NPR, The Washington Post, and other major news organizations reported on the study, amplifying the finding that consumer-grade fitness wearables are generally inaccurate when calculating calories burned.

  2. 1

    FIU study publishedSmartwatch calorie measurements unreliable, worsen with body fat

    Jason Kostrna and colleagues at Florida International University's Medical Photonics Laboratory released findings from a study of 58 participants wearing four popular smartwatch models during controlled cycling sessions. Researchers measured actual energy expenditure using metabolic analysis and compared it to each watch's calorie estimate, finding all four devices demonstrated substantial error that increased with wearers' body fat percentage.

    “Our team found that not only can these devices err substantially in their measurements of calories burned, but those errors also increase as the wearer's body fat percentage rises.”
    — Jason Kostrna
    1. 1 outlet The higher your body fat percentage, the less accurate your smartwatch is at measuring calories you burn when exercising – new study

      first by The Conversation US, 2d ago

Also covered reported alongside — the timeline has no entry for these yet

  1. 4 outlets Why your smartwatch is so bad at telling you how many calories you burned

    first by The Washington Post, 1d ago · also NPR, NPR Health, The Conversation

    2 more headlines

and 3 smaller pieces