I decided to use the Halo, a Fitbit bathroom scale, and a highly rated skin slider to record consistent body fat measurements for myself and a friend. In November and December, I took measurements early in the morning with the halo and bathroom scales. My wife pinched my skin folds in four areas with the caliper. I measured the body fat of my test person once with each device.
Our results were remarkably similar for two men with very different body compositions:
The Amazon product estimated that my friend, a 6-foot-3 man who weighed 198 pounds, had 24 percent body fat, the Fitbit scale 19 percent, and the skinfold measurements 20 percent.
For myself – 5-foot-6 and about 140 pounds – in November the Halo said I had 25 percent body fat, the Fitbit scale 19 percent, and the skinfold measurements totaled 20 percent. In December, the Halo said I had 26 percent body fat (sadly, I had more Thanksgiving leftovers than usual), the Fitbit scale said 20 percent, and the skinfold readings totaled 21 percent.
Dr. Cheskin speculated that the halo might have an overestimating bias in its algorithm, since underestimating body fat would be more of a problem for an obese person.
Dr. Maulik Majmudar, the Amazon medical worker who worked on the Halo, said people should expect the device's results to be different because the method was more accurate than body fat scales and calipers.
Amazon developed its body measurement algorithm from a sample set of tens of thousands of images of people's bodies from a variety of demographics, he said. Amazon then ran internal tests that measured people's body fat using the Halo scanner, smart bathroom scales, and DEXA. This technique uses X-rays to scan bone density. Studies have shown that this is a reliable measure of body fat. The Halo method turned out to be twice as accurate as the bathroom scale.
Still, Dr. Cheskin is not convinced of Amazon's accuracy requirements. He said a valid study would include a clinical study measuring the body fat of many human subjects using any method – Halo, DEXA, bioelectrical impedance scales, and vernier calipers – and comparing the results side by side.
Exactly or not, the most disappointing part of Amazon's body fat analysis was that it lacked an important context. Although the app asked about my ethnicity, age, and gender, my body fat percentage was 25 percent too high and way outside the “healthy” zone (around 12 to 18 percent). It is also said that healthy outcomes are associated with longer lifespan and lower risk of heart disease.
Dr. Cheskin offered a more nuanced analysis. Body fat levels can have different health effects based on age, ethnicity, gender, cholesterol levels, and family history. Waist size also plays a role, as heavy belly fat can be linked to health problems.