Garmin calorie reading.

Wheely GR8

Hi ,today was the first day I did a long cycle with my old garmin edge 205. It said I spent 3500 calories ,but I'm wondering how accurate it is ?

I did notice it didn't increase when I was going downhill.

Tau

In short, its not very accurate. A lot of not very accurate calorie counters seem to default to an assumption of 1000 cal / hr, with some of them additionally excluding time spent coasting, or going downhill. Were you cycling for about 3.5 hours?

This is worth a read for more detail:

http://www.dcrainmaker.com/2010/11/how-calorie-measurement-works-on-garmin.html

The edge 205 uses a speed / distance method only which is described as:

Speed/Distance Algorithm: This is the most basic method of determining calories, as it is only used when a heart rate strap is not enabled/used (default). Given the lack of heart rate data, the unit will simply use speed/distance, as well as the weight you entered in the device setup. The reason this is less accurate (65-80% accurate) is that it can’t differentiate how much effort you’re expending to travel a given distance – which while less important for running, is quite important for cycling. For example, if you’re coasting down a 7 mile descent, you’ll burn virtually no calories compared to ascending the same mountain. This speed/distance algorithm does not consider or evaluate the impact of elevation change – primarily due to concerns the team had about relying on GPS-based elevation to determine calories. They also reasoned that while the Edge units had barometric altimeters, it was better to focus on heart-rate based calorie burn, as opposed to simply expanding the ‘guesstimate’ that the speed/distance algorithm is. Finally, note that if you wear a heart-rate monitor/strap – speed/distance are ignored, and instead one of the other above (more accurate) methods are used.

Wheely GR8

I'm on my phone so will check the link tomorrow ,I was cycling for around 3 hours and did 75km

My weight is 100kg and I'm 5'8''

Wheely GR8

I did notice though it didn't add calories when I was descending ,maybe in an update they added the elevation into the equation.
I do coast a little though.

Ah well ,I didn't eat much today. Only had abot 1400 calories

Ryaner

I've a powertap on my bike which outputs a value based on the power you output across the ride. Its meant to be fairly accurate as its based on kilojoules. Comparing it to the Garmin calorie figure shows the Garmin way overestimated things. On shorter cycles I was noticed 2-3 times increase. Longer ones (8+hours) were closer to 1.5 - 2 times increase.

Beasty

We've had a number of threads on the Edge 305 and 705, with a general consensus the "real" calorie output is perhaps 50-60% of the figure estimated by the Garmin

However the Edge 500 and 800 are pretty accurate (and I've tested both against the energy output estimated by Powermeters)

Wheely GR8

I did think 3500 was OTT for the work I done. I'm best off ignoring this for the moment and just rely on mileage,

Thanks.

Wheely GR8

I got my winter bike a couple of weeks ago to loose weight and if I loose enough I'm buying myself a carbon.
Thats why I'm reluctant to spend on anything non-essential until then, otherwise I'd just buy the 500

Thanks for the replies

Cookie_Monster

Beasty wrote: »

However the Edge 500 and 800 are pretty accurate (and I've tested both against the energy output estimated by Powermeters)

accurate off the shelf with a few personal details entered (weight, height, age etc) or do you really need a HRM etc?

I ask only because of the sheer number of calories I've burned would imply to me I should have lost a lot more weight than I have

Beasty

Cookie_Monster wrote: »

accurate off the shelf with a few personal details entered (weight, height, age etc) or do you really need a HRM etc?

I ask only because of the sheer number of calories I've burned would imply to me I should have lost a lot more weight than I have

I understand they are supposed to take HR into account. I run them alongside the Cyclops Joule, which accurately records energy expended in Kj, which is pretty close in number to the Garmin calories (which it should be)

smacl

Without a HRM or power meter, I think there are too many variables not accounted for to get an accurate value of calories consumed. e.g. gradient, wind resistance, rolling resistance, etc... For myself, on the turbo trainer, working reasonably hard, the power output suggests about 820 Kcals per hour for a 32kph average speed and mixed resistance. On my more relaxed longer spins in the hills, HRM suggests about 650-750 Kcals per hour.

>1000 Kcals per hour is a serious amount of work, but for your 100kg not beyond the realms of possibility according to this chart. Your 25kph = 15.5mph, and your 100kg = 220lb, which lands you at 931 Kcals per hour in that chart.

Any way, 75k in 3hrs for a 100kg fella is great work so well done, and don't expect to stay 100kg for much longer if you're managing that regularly.

AstraMonti

Beasty wrote: »

I understand they are supposed to take HR into account. I run them alongside the Cyclops Joule, which accurately records energy expended in Kj, which is pretty close in number to the Garmin calories (which it should be)

Are you displaying power in garmin as well?

Beasty

AstraMonti wrote: »

Are you displaying power in garmin as well?

Yes. The Joule gives me additional real time info such as Normalised Power. I'll have the Garmin displaying 3s and 30s averages.

AstraMonti

Beasty wrote: »

Yes. The Joule gives me additional real time info such as Normalised Power. I'll have the Garmin displaying 3s and 30s averages.

Maybe then it takes in account both HR and power and that's why you are getting accurate calorie readings?

Beasty

AstraMonti wrote: »

Maybe then it takes in account both HR and power and that's why you are getting accurate calorie readings?

Don't think the Garmins are that sophistcated. I got similar readings when the PM battey was dead. It's just the 500 & 800 I'm talking about here, and I think there's a general consensus they are much better than the 305 & 705 at calorie estimation.

niceonetom

I think it's generally accepted that kcal values generated by whatever formula the previous generation of garmin are junk. That's probably sabotaging some out there who want to use those values to help them lose weight. Some people enter their bodyweight in as half what it is to make the values a little less likely to inspire a fridge raid.

I'm glad to hear from someone who can actually compare PM and HR based calcs that the new algorithm the 500/800 generation uses is reasonably accurate, or at least correlates roughly with the PM which is, of course, just another estimate. One thing I'm curious about is how you, Beasty, or anyone else who has both a X00 and a PM to corroborate is what you entered for the "Activity Class" in the Garmin user profile. I assume this is some sort of weighting value that'll skew results upwards for the unfit and downwards for the mercilessly efficient. What value have you put in there to get the correlation you've seen?