Why is there a big discrepancy between some calorie burned estimates?

Factual Questions
1

The question is in the title. An example, today I rode 35 kms on my mountain bike, it took me 1:25 for an average speed of 25 kph. My Cateye gadget on the bike said I’d burned 605 calories, however when I put the same data into the website MapMyRun it estimated the calories burned at about 1200. Twice as much as what the Cateye told me. Why would this be? Although I used MapMyRun, I input the data as a bike ride, not a run.

One other thing, MapMyRun knows how much I weigh, while the Cateye doesn’t.

2

I was involved in a study with the sports med dept at the U of Chicago and it found those calorie counters on machines in gyms were horribly inaccurate. The best one came about 60% correct, and others were only 20% correct.

A lean person do rapid aerobics for 60 minutes is gonna burn about 300 calories. Now you’ve seen these people sweat and how hard rapid aerobic exercises are. 230 calories is two peanut butter cups. So you can see why it’s so hard to lose weight with just exercise.

Another myth is the swing arms or the weights in arms. That burns very little extra calories. It burns about 10% more. So if you execise with weights you’re gonna burn 330 calories instead of 300 calories an hour.

You have a much higher rate of injury from the extra weight, (such as dropping it on your foot or pulling your muscle) than you have from any benefit you might gain by using the hand weights.

Again these are general guidlines.

The more you weigh the more calories you burn. Muscle weight and fat weight also influence how many calories you burn.

Bottom line is you don’t lose much weight through exercise. You’ll be lucky to lose ten pounds. So use exercise to work out your heart and/or lungs or for stress relief and use diet to shed the pounds

3

Thanks for the interesting information, though it doesn’t really address my question. Presumably both my Cateye and the MapMyRun wesite are using common methods for estimating calories burned. Are there standard methods for doing this? Why would they be so wildly different?

4

As a point of reference this website lists different exercises and weights and gives the calories burned. Those figures are far more in line with the mapmyrun website than my bike gadget. The only thing I can think of is that the Cateye assumes I’m a lot lighter than I am (I’m 200 lbs BTW.)