A new model of accuracy: Amazon Halo Body feature
by the Amazon Halo team
Whenever we launch a new product or service at Amazon, we conduct months — often years — of rigorous testing with the goal of providing the best possible customer experience. In many cases, and certainly in the case of health and wellness services like Amazon Halo, an important part of that testing focuses on achieving a very high standard of accuracy, because a tool like the Halo Body feature is only useful if it’s highly accurate. With that in mind, we are excited to share some news about Body with you today.
Wait, step back — what’s Body?
For anyone new to Amazon Halo, Body is a feature within the Halo membership service that allows you to easily (and accurately!) measure your body composition from the comfort and privacy of your own home. Using only your Halo app and smartphone camera, you take a body scan consisting of four images: the front, back, and two sides of your body. Within seconds, you’ll get your body fat percentage (BFP), a personalized 3D body model, and an interactive slider tool to see how your body shape could change as your body fat percentage changes. Typically, getting your body composition measured requires access to expensive commercial-grade tools like hydrostatic dunk tanks and pods or clinical-grade tools at a doctor’s office — or compromising on accuracy by using an at-home smart scale. The Halo Body feature uses innovative new machine learning technology to democratize access to this important health information. You can learn more about Body here.
Why should I care about my BFP?
BFP is a better overall indicator of health and longevity than weight or body mass index (BMI) alone because, at the most fundamental level, obesity is synonymous with having too much body fat. This is not a new idea — medical professionals have known this for some time[1] — but until Halo, there hasn’t been an easy and accurate way to measure BFP, so clinicians have relied on BMI as a proxy, knowing that it can’t distinguish between fat and muscle the way Halo and other tools that measure body composition can. Because of that, you’ll often see professional athletes or bodybuilders characterized as obese on the BMI scale. Or at the opposite end of the spectrum, certain communities can be characterized as healthy according to BMI, but actually tend to have elevated levels of BFP, and therefore go underdiagnosed for things like prediabetes and heart disease. In short, unless you’re accurately measuring BFP, you aren’t getting the best, most useful understanding of your health and wellness.
So how accurate is the Halo Body feature?
This is the key question—a tool like this is only useful if it’s accurate. As I mentioned above, we hold all of Amazon Halo’s health metrics to a very high internal bar, but we wanted to go beyond that for Body given the novel approach to estimating BF and test it in a clinical setting. So we recently completed a clinical study led by Dr. Steven Heymsfield, MD, of Pennington Biomedical Research Center (PBRC) and Dr. Fatima Stanford, MD, MPH, MPA, MBA, of Massachusetts General Hospital (MGH). You can read the full study manuscript here[2], but to sum it up, the study confirmed what we learned via our internal testing: you can get an accurate measure of BFP using the Halo Body feature. In fact, the study showed that Halo is as accurate as methods a doctor would use, and nearly twice as accurate as leading at-home smart scales.
How did the study work?
The teams at Pennington Biomedical and MGH tested a diverse group of 134 participants in their labs (that may not sound like a very big number of participants, but the study was adequately powered to show statistical significance). Each participant underwent body composition assessment with multiple devices: Body (Halo), three currently available consumer bioelectrical impedance analysis (cBIA) systems (aka at-home smart scales), two professional BIA (pBIA) systems, air displacement plethysmography (ADP aka pods), and dual-energy X-ray absorptiometry (DXA). Body fat estimates from all devices were compared to the results from the DXA device because DXA is the clinically accepted gold standard for measuring BFP. It’s important to note that members of our team at Amazon were not involved in the data collection and did not have access to the ground truth results from DXA until after Halo’s body fat estimates were shared with the principal investigators, Drs. Stanford and Heymsfield. Once all of the testing was complete, they returned the results to us, and Dr. Heymsfield, Dr. Stanford, and our teams analyzed the data and prepared the manuscript together.
What does this mean for me?
Any health and wellness journey requires two important elements: information and action. At Halo, we believe in leveraging the power of Amazon’s technological know-how to provide our members with the most relevant health information possible. That’s what Body is all about — arming you with accurate, clinically relevant information about your body composition that can help you (and your care provider if you choose to share with them) decide how to proceed on your unique health journey. We know that sometimes new information like this can be challenging to take in, but you can rest assured that it is accurate. And of course, at Amazon it’s always Day 1. Which means the Body feature, and all of Halo’s tools and features, will continue to get even smarter and more accurate over time.
[1] Padwal R, Leslie WD, Lix LM, et al. Relationship among body fat percentage, body mass index, and all-cause mortality. Ann Intern Med 2016.
[2] Majmudar M, et al. Smartphone Camera Based Assessment of Adiposity: A Multi-Site Validation Study. Medrxiv preprint 2021.
