Variable Outcomes

I have been tracking data for a few months now, and there is one thing that is really frustrating me - variable outcomes.

On my phone I have Argus, Withings and MyFitnessPal, and they are all configured to ‘talk’ to each other. I use a Withings Pulse in conjunction with the app.

Argus and the Pulse both track my step count. They are always different by about 10%, but I can accept that this is a reasonable variation over the course of a day, especially as I am a fairly active person (I average around 18-20,000 steps per day).

What I find harder to understand is the HUGE variation in calories burned. At the moment the three apps are reporting the following calorie burn for today:

Argus: 1758
Withings: 2414
MyFitnessPal: 1247

The really weird thing is that MyFitnessPal gets its data from Withings!

Can anyone explain the discrepancy to me? I tend to think that maybe Withings includes my BMR, but even if that is true the figures still vary by as much as 50% on any given day.

Estimating the number of calories burned from a step count is bound to be inaccurate to the point of being useless (even after factoring in body weight etc). So if that’s a data point you care about, consider getting a device like the BodyMedia FIT?

So the Withings Pulse is…useless?