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I've been working out by running around the neighborhood lately, and I've been tracking my runs on two running sites, as well as keeping track of the calories on MyFitnessPal. However, I've been confuzzled lately about the calories that I should be tracking on my calorie tracking. For example, for a recent 46-minute heavy interval run, I get:

These numbers are wildly different, and I don't want to over or under-eat calories based on my diet. I would think that RunKeeper, which actually keeps track of my pace using the GPS and elevation would be better because of more data. Lately I have been trying to under-estimate by using the lowest of the three that come up.

Which number should I be trusting? Are any of these numbers worth anything?

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did you just use a GPS or did you also use a heart rate monitor? – Ivo Flipse Nov 12 '11 at 8:30
The RunKeeper run is tracked with the GPS on my phone, which is in my pocket. It's not always accurate because of trees on the route, sometimes overestimating. The Dailymile route was mapped by hand so it's fairly accurate. – jamuraa Nov 12 '11 at 15:56
The route may be accurate, the pace at which you traveled may not be :-) Either way, without knowing your heart rate or oxygen consumption estimating your calories is really a wild guess. – Ivo Flipse Nov 12 '11 at 16:04
Well, I'm taking the time from the Runkeeper which is recorded on my phone (and I've tested independently to be accurate at at least keeping track of how much TIME it takes) and put it into Dailymile, so shouldn't the average pace still be correct? – jamuraa Nov 12 '11 at 16:53
Well only if your route is flat and your speed is perfectly distributed... – Ivo Flipse Nov 12 '11 at 17:35

3 Answers 3

up vote 5 down vote accepted

They're worth a teeny bit :) It's a very rough estimate, and depends on all sorts of things, even the weather. (Perhaps not the phase of the moon.)

That said, the lower number is closer to what I'd expect.

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Totally agree with @DaveNewton here; as an added query, why are you tracking calories burned? Are you comparing them to caloric intake? If you're just tracking runs to compare distance/time then I wouldn't worry about the calorie count at all :) – Jedidja Nov 11 '11 at 17:02
I'm trying to track because I am indeed keeping track of my caloric intake versus expenditure in order to make sure that I am losing (well, maintaining now) weight over the long term. Basically the idea is that I should be replacing those calories with food to meet my daily calorie goals. – jamuraa Nov 11 '11 at 20:15
@jamuraa To be honest, I'd just use a scale. – Dave Newton Nov 11 '11 at 20:18
By a scale do you mean something like a FitBit, or are you suggesting that I should be able to figure out how many calories I expend by averaging over some weeks of weight data? I am confused. :/ – jamuraa Nov 11 '11 at 20:53
@jamuraa I mean stand on a scale, and see if you're losing/gaining weight, and adjust accordingly. There are so many factors involved that even projecting an "optimal" caloric intake value is likely to be wrong essentially all the time. It's a long-term process predicated on consistency and general behavior, not easily quantifiable for small timescales. Jesus, what happened to that sentence?! – Dave Newton Nov 11 '11 at 20:57

The sites obviously have different ways to calculate the final count. Check and see if they accept inputs like Effort required (which does not have any unit of measure), Your weight etc. If the measurable quantities are identical in all, then the formulas are different.

You can take the average :)

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The short answer

Neither site is very reliable for how many calories you actually burned since none tracks your heart rate and their methods of measuring distance are not necessarily reliable. You will have to guess based on how hard you felt you worked out. It's probably closer to what runkeeper gave you, if I were to guess without knowing your level of fitness.

The long answer

Burning calories is very individual and one's metabolism can't be guessed by those sites. Heart-rate does give a somewhat good indication of how hard you're working out, but it still doesn't tell us how your metabolism actually work.

Why GPS and Maps may be bad

First and foremost; GPS is not very accurate and thus the route can be very different from what you actually run (the more expensive the GPS the more accurate the result) and the GPS doesn't know if you're running on a flat, inclined or declined surface. You could run up a mountain and the GPS wouldn't know.

Maps may also be the same as the GPS on the point that it may not account for the hills, and the distance can thus also be distorted, though it is my opinion that maps are more accurate than GPS.

Why heart-rate monitoring is good

You could run X km in XX time, but depending on your level of fitness, you will work differently hard and burn differently many calories. Tracking your heart-rate as far as I know the best way of measuring how much you're burning since it measures how intensely you're working out. You can then make an assumption based on the average person and perhaps modify the calorie count according to your metabolism. If you have a fast one you may wanna add a few calories and subtract a few from the norm if your metabolism is slow.

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