https://www.theatlantic.com/health/archive/2014/06/can-you-s...
Also the reviews on Amazon are pretty bad.
If they do claim that it works based on noninvasive blood glucose monitoring that's also a red flag; many have tried to solve that problem, and the obvious application would be a monitoring device for diabetics.
and supposedly they have improved the device in generation 2 which I'm currently testing. Sleep, step, hydration status and heart rate tracking work well, based on these reviews, a science article on bioimpedance and non-invasive glucose monitoring https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3500977/ I have hope I can confirm that calorie tracking works.
Tech like this is a major breakthrough. It's just not something you see come from a crowd funding campaign. I'm extremely skeptical.
Be interested to know what your personal experience with it is though. Best of luck.
On the calories expended side, the clear winner is a power meter on a bicycle. The power meter measures actual power output and energy expenditure, which is easily and accurately converted to kCal.
For the indirect devices, it's a massive mixed bag with some very unexpected observations. Measuring galvanic skin response ended up being quite inaccurate. Garmin devices without a heart rate strap were insanely inaccurate, sometimes reporting 300% higher-than-actual calories expended. The best device has actually been the Apple Watch paired with an iPhone. The calories reported are usually within 5% of actual.
As for the devices claiming to track calories ingested, every device has been either outright fraudulent or, at best, vaporware.
In your ankle weight scenario, the added weight would, in effect, cancel out. You'd get a free boost to power output for 50% of a pedal stroke, and added resistance to the other 50% of the pedal stroke. These forces are being applied simultaneously on either side of the cranks. While one side is combating the added weight, the other side is feeling the boost of the additional weight.
And sure, there are additional caloric expenditures while cycling - increased heart and respiration rate, utilization of muscles in your arms and torso, etc. - but they are marginal compared to the generation of 300-400W using, primarily, the muscles in your lower body.
Further, these differences are factored into the athlete's efficiency in turning calories into mechanical output. A trained cyclist is 25% efficient.
You seem to be attempting to be deliberately obtuse.
Unless of course you are machine running at 100% efficiency. (The only 24% efficiency factor for humans is based on so many assumptions)
Only real way to measure energy expenditure accurately is using breathing measurements. VCO2/VO2
Sure, the power meter under reports total expenditure. For example, it doesn't exactly account for BMR, increased expenditure due to elevated heart and respiration rate, utilization of muscles in your arms and torso, etc.
However, it is extremely accurate compared to the alternatives.
If there is no potential for harm (like with medications), throw it out there and see what happens. The market will validate the technology, one way or another.
Yes, you shouldn't trust such a device completely. But if you can't trust it... What's the point, other than an expensive cool toy?
Edit: the article the person above linked to includes exactly that
> When the first GoBe band was released in 2014, it was the target of some harsh criticism. The medical blog The Doctor Weighs In, for example, made this call based on Healbe's marketing pitch [...]