Index S2 Smart Scale – Garmin Sued Over Body Composition Accuracy Claims

Thanks to Dan for the heads up!

A proposed class action filed in the US District Court for the Northern District of Illinois on 29 May 2026 aims at the Garmin Index S2 Smart Scale. The case is Maurer v. Garmin International Inc. et al (1:26-cv-06389).

This case is starting to be reported for the device’s inaccuracy. That’s not strictly true. What’s really being tried here is whether Garmin misrepresented what its product could deliver. What’s at stake initially seems to be the class-action claim for $ 5 million plus costs. However, that’s not the case either; that’s a threshold limit, and if the plaintiff wins, the amount could be substantially higher.

Let’s cut to the chase. Here is the essence of Maurer’s allegation and the likely rebuttal from Garmin. An hour-long episode of The Good Wife based on this case would pretty much boil down to these 11 bullet points.

The allegation

1. Foot-to-foot BIA sends a current from one foot to the other, measuring resistance only through the lower body. It cannot accurately capture whole-body composition.
2. Garmin marketed the Index S2 with unqualified accuracy language and positioned body fat, muscle mass and related metrics as reliable outputs.
3. A 2021 peer-reviewed study in JMIR mHealth uHealth found that foot-to-foot smart scales underestimate fat and muscle mass by up to 8kg compared with DEXA, the clinical gold standard.
4. Garmin failed to disclose the technology’s fundamental limitation to buyers.
5. The plaintiff argues that every Index S2 purchaser was therefore misled. The complaint seeks monetary damages exceeding $5 million.

The rebuttal

6. The JMIR study tested a Tefal, a Terraillon and a Withings scale. A Garmin was not tested. No Garmin-specific error rate can be drawn from it.
7. The 8kg figure is a worst-case outlier from a clinical population recruited specifically because of obesity or chronic illness. Median errors in the same study were 2.2–4.4kg.
8. The Garmin Owner’s Manual cautions that hydration and activity affect measurements and recommends consistent conditions for best results.
9. Every major competitor (Withings, Fitbit, Tanita, Eufy) uses the same foot-to-foot two-point BIA. If the technology is the problem, Garmin is not uniquely culpable.
10. The industry-standard position is that BIA scales track relative change over time, not absolute clinical values.
11. “Exceptional accuracy” in Garmin’s launch statement referred to the scale’s overall accuracy, which measures weight to within 0.1kg. The complaint must demonstrate that the claim was applied specifically to body composition.

Assessment

The plaintiff’s weakest point is the science: the key study does not test Garmin’s product and draws its error data from an unrepresentative clinical population. The study might show that this general class of products has inherent weaknesses.

Garmin’s Achilles heel is its own marketing copy. The official blog states the scale delivers results for users because “Garmin believes that accurate data is important” in direct reference to body composition outputs. Even worse is the launch statement from Garmin VP of worldwide sales Dan Bartel: “The Index S2 builds on the success of the first-generation Garmin smart scale with exceptional accuracy.” Unqualified. In a product announcement that leads with body composition as the headline feature. That is the sentence the plaintiff’s lawyers will return to.

My take is that Garmin has a decent chance of losing. I’m not a lawyer. However, consumer fraud cases do consider the overall impression created by marketing, not giving brands a get-out-of-jail-free card with a disclaimer buried somewhere in a voluminous manual. The “everyone else does it too” defence might help Garmin, but the specific statement from a named executive making an unqualified claim of accuracy at launch won’t.

Garmin’s words are its biggest liability, not its product.

The case, Maurer v. Garmin International, Inc., et al. (1:26-cv-06389), was first reported by Singletracks.

FAQ

Q: Does the Garmin Index S2 accurately measure body weight?

A: Yes. Weight measurement is not in dispute. The lawsuit concerns body composition metrics — body fat percentage, muscle mass and related outputs — not the scale’s ability to measure weight.

Q: What is foot-to-foot BIA, and why does it matter?

A: Foot-to-foot BIA sends an electrical current from one foot to the other, measuring resistance only through the lower body. A four-point system that uses both feet and hands measures more of the body directly and is generally considered more accurate for body composition.

Q: Has Garmin responded to the lawsuit?

A: Not publicly at the time of publication. The case was filed on 29 May 2026 and is in its early stages.

Last Updated on 5 June 2026 by the5krunner

the5krunner

tfk is the founder and author of the5krunner, an independent endurance sports technology publication. With 20 years of hands-on testing of GPS watches and wearables, and competing in triathlons at an international age-group level, tfk provides in-depth expert analysis of fitness technology for serious athletes and endurance sport competitors. ID