A calorie tracking conundrum - Stages Power Meter

Last year, quite successfully, I lost a bunch of weight by intimately tracking my calories using expended KJs from my power meters - indoors via a Wahoo Kickr and outdoors via a Stages L only power meter.

This year, after injury, I’m in the same place again where I need to work on the weight but instead of summer it is winter, so I picked up a new Stages L only Power Meter for my winter winter bike. It’s a new generation of crank (Shimano 12 speed) but the same gen of Stages as my summer bike.

I’ve just got back from a spin on my usual 100km loop, and the tracked expenditure vs a pretty large portfolio of sample rides from the summer is approx 1000 calories more over the 100km. Or another way round, approx 5-6kph slower today is about the same expenditure as some of the real big efforts last summer. A 28kph spin vs some real pushes at 33kph avg.

Obviously I’m running a couple of KGs heavy so I would expect to be pushing a few more watts but the spread to a tonne of previous example just seems wildly off -
30-40 watts on the same climbs.

So now I have a weird conundrum to try and work out, was I grossly under tracking last year, and this just making the pace of my weight loss really fast, or is my new Stages reading really high and I’m screwing myself over. I’m trying to run around 600 calories deficit, so if I knock out every ride on my standard loop and that’s 1000 calories higher than the sort of numbers I was tracking last year then I could be putting myself into a surplus rather than a deficit!

I popped the new crank bike on my Kickr and the numbers tracked around 10 watts under, so at first blush I’m hoping I was under tracking last year. I can’t do the same comparison for the summer crank as I don’t have the mounts to get it on the same Kickr, so cautiously wondering what to do.

An interesting conundrum, and a common issue trying to compare different power meters, but pondering what to do

No response to your core question, but I am always a bit surprised when I see this assertion. I have owned/used/extensively tested PowerTap (multiple), SRM (also multiple), Quarq (ditto), and Garmin (still using the original ones gifted to me) power meters, as well as multiple Velodyne trainers. All have agreed quite closely, at least when you took drivetrain friction into account. I can only conclude that folks who believe that each power meter is a standard unto itself have had their thinking influenced by what they have read, other brands (although Assioma are quite popular, and have a good reputation), and/or modern “smart” trainers, which seems to have traded accuracy for profit or other bells-and-whistles.


Yes I understand and would also agree, that was my general feeling too, hence just buying another power meter for my winter bike (rather than swapping between bikes for example), I get that there would be some spread, but the discrepancy here just seems so wide for such a familiar ride route I’m wary to trust the numbers off the gun,

To all of a sudden see an expenditure for a very familiar loop jump by 1000kjs has me concerned I’ll be on the wrong side of my tracking, but then I was also surprised to see it mapped pretty well to my Wahoo kickr.

I’m tempted to do a crank swap with the old one off the summer bike on consecutive days just to test out my theory, assuming I can go out and ride a similar pace. And I can try it on the kickr for comparison too.

Compare both power meters to the Kickr and then you will know.

It’s hard to believe that it’s off by a full 1000 kjs. Maybe there is a setting? Where are you getting the Kj total from?

This may not explain the entire difference, but because of various difference in bike set up, what we’re wearing, road conditions, air conditions, etc. we are slower in winter for the same power output. E.g., on a local climb I put out record (for me for that climb) power this past week, but it still didn’t make even my second fastest time on that climb.

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Don’t discount the impact of low temps. Tires can get significantly stiffer in the cold, and the air is denser from both low temp, and the typically lower humidity of cold temps. I doubt that would cover the whole 1000 cals, but if the new PM is a couple % lower than the other, with all the other stuff, it could account for a lot of it.

As others have said, your best comparison is to check both meters against the trainer. You won’t know which is “right” but you’ll know the relative power of each.



Benchmarks like this are fraught with complications:

  • How windy was it in comparison? On flat routes, wind is a big, big factor.
  • How much more do you weigh now compared to before? If there are smaller climbs peppered in, additional weight may play a role.
  • You have a one-sided power meter. After I upgraded from a single-sided 4iiii power meter to a Quarq, I learnt I had a significant leg imbalance. So if your left/right balance is lopsided in favor of your left leg, then it appears as if you put out more power even though you don’t.

If you are really unsure, I’d get either a Quarq power meter (which you can use with Shimano chain rings) or Assioma Duo two-sided pedal-based power meters. I also heard good things about e. g. Rotor’s power meters, at least for outdoor rides they seem to be spot on.

In principle you are right, although the fact that OP has a single-sided power meter can change that to some degree. The actual power measurement may be completely accurate (i. e. it really does measure the power of OP’s left leg within spec), but he may have a larger leg imbalance.

My (much more limited) experience is that trainers are less stable than power meters. My Elite Suito was dead on with my Quarq when it was new. But after a year or a year-and-a-half, both offset and slope were measurably off (think 30 W at threshold). I reckon that while factory calibration of my Suito was spot on, for some reason they would have to be recalibrated. (Before anyone asks, yes, I did do spin-down calibrations several times when the trainer was warm.)

Lacking any other power meters, I decided to simply trust my Quarq and never use my trainer’s power numbers.

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Yeah, I didn’t want to point a finger too directly, but I think it is clear that many/most newer entries into the market place often don’t measure (although there were some clear failures back in the day as well, e.g., Ergomo, CompuTrainer). What’s sad is how this has led people to believe that no power meter (or trainer) is accurate/precise, such that it doesn’t matter, when it is the most important thing.


just throwing this out there. since this is the internet and you did ask hah. I have a lot of personal experience with weight fluctuations and my last stint really worked well for me (went from 275 to 190 lbs starting 5 years ago - ended 3 years ago and have maintained successfully)

you should have a good feel for the quantity of food you ate last time, right? I think you would notice if it’s 1,000 calories off.

when I am in a fat loss phase I try to really consolidate my foods to make it easy on myself. especially since tracking whole food calories (which is what I prefer eating) is pretty inaccurate (i.e. can’t really track calories in a rib-eye due to differences in fat content, etc). you probably already know that even packaged food can be 15% off.

personally, and i’m not trying to impose my values on you…just telling you personally what I did. I tracked for a while to get a good feel for stuff, then ate off of using my eyeballs, my body weight, how my clothes felt, how I felt. I’ve been in maintenance for a few years now (within + - 5 lbs for 3 years) and I never count anything. worst case if I go to my upper limit I remove my “treat” type foods for a week or two.

i believe there is great benefit to learning to eyeball it and control it this way. sorry dunno your injury but if you are so injured you don’t feel like counting calories, or you’re depressed about it, or focused on recovery, etc…being able to eyeball things is useful. so like 3 months ago I got forced off the bike due to injury…I know what my A+ diet looks and feels like. I went into A+ diet mode without having to weigh and track etc.

again to me “eyeballing” comes after many months of tracking / weighing / seeing those numbers work…and eating similar foods. i’m not talking about “intuitive” eating for weight loss. you are technically “tracking” I guess

I dunno…I’d give that a shot

but yeah your power meter is messed up. i’d want that fixed (or confirmed your old one was messed up) if you’re putting in massive hours and relying on it for data. sry…sounds like a huge pain.

It is surprising how even the major players (Tacx/Garmin, Wahoo and Elite) have been struggling when they released minor spec bumps of existing trainers. Maybe I also made a mistake by getting the cheapest trainer at the time, but on the other hand, power accuracy over time is not a new thing and should be table stakes. It is quite disappointing.

I’m glad I have a Quarq that I trust. Apart from the battery cap rusting in place, I have had zero issues with it so far. I wish there were a way to calibrate (≠ zero) the power meter every once in a while. For the moment, I have to steer away from these thoughts … :wink:

Do you keep a list of power meters you trust? Is there any deviation from the recommendations by @dcrainmaker and @GPLama?

Speaking from my experience, I’d like to add to that:

  • Intuitive eating works, once you have calibrated your perception of satiety a little.
  • Once you intuitively eat to keep your weight more or less balanced, I nudge a little to lose or gain weight. I might cut my breakfast by a slice and be strict about not buying chocolate. That’s usually enough.
  • Another hack to see whether you are really hungry for another portion/dessert or you’d end up eating more than you need is this: just wait for another 5 minutes and see whether your hunger subsides. You don’t have to “win” every time either.
  • Avoid big changes, e. g. big calorie deficits or cutting out meat/animal products altogether in one go. I have been trying to eat less processed meat in the morning, and I have achieved that without feeling it too much.
  • There is a virtuous cycle: when I train, I tend to crave healthier food and have less desire to eat junk food.
  • I like to weigh myself often, and I have learnt to not take the numbers that appear too seriously. It is about averages and trends. Some foods take longer to digest, and I’m just heavier, because I have more food in my digestive tract. When I lived in Japan, eating ramen meant that I weighted 800–1.200 g more the next day. However, if scales give you anxiety, find a way to integrate them.
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we may have different definitions of what “intuitive eating” means…because I agree and do 100% of what you wrote.

to me intuitive eating is someone who eats a very wide variety of foods and quantities based on what they feel their body is craving.

not knocking that method at all…just for me personally when losing weight it was easier to stick with similar foods so I could eyeball quantities better…or like you, cut one thing out for a few days or weeks if I put on a few lbs.

I would be happy (mostly) with any of those I listed. But, it would depend a bit on the specific application.

Analogously, I have always been rather impressed by the MOXY NIRS monitor, at least when you consider the cost and intended market (i.e., athletic individuals who are likely to be lean enough that the limited distance between the optodes isn’t a major issue). However, just a couple of days ago we dual-recorded using a MOXY and a research-grade $35k NIRS device when using the approach described in this paper to non-invasively estimate muscle respiratory capacity:

Unfortunately, the MOXY data proved to be too noisy/have too low of temporal resolution to be usable. Similarly, there some specialized things (F-V testing) you can do with an SRM that you can’t do with a PowerTap or Quarq…see the four part series starting here:

I have no idea what others recommend.


That’s not what intuitive eating is.

Eat when hungry and stop when full; something innately felt by listening to our body’s cues. We were not born measuring portions, tracking macros, or counting calories, and we did not pay attention to any external forces telling us what we should or shouldn’t do to be healthy or thin. The drive to eat, or stop eating as a baby was fully intuitive.

The problem is when you’re getting cues to eat, but choose the wrong foods, those cues persist or reoccur frequently.

maybe there are different definitions. this is from webMD:

so yeah I stand by what I said then. I think measuring > feeling for losing weight (for me like I said, I measured with a scale then “measured” with my eyes). it could take some people a LONG time for your hunger signals to tell you the proper portions.

that’s just what works for me. if I ate til I was full I would never have lost weight. I think I messed up my internal hunger signals and it took me a long time to re-calibrate it (like several years). I think hunger is just part of the deal when losing fat

(again just my opinion based on what worked for me…i’m not a scientist or anything)

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I must admit I don’t find it particularly easy to keep things in check on my own but given my training loads of 20-25 hours a week I do find there is simply a lot of eating going on and keeping track of things has helped me keep things in check, it would be ideal to not do it, but I’ve not found it particularly taxing to do.

The next few weekends will be power meter comparison sessions on the turbo trainer I think!

I also appreciate the advice on the spider based power meters, I suspect I’ll probably pick up something comprehensive like an SRM at some point

I don’t have a strong opinion on what constitutes intuitive eating, I just tried using it the way I saw it used elsewhere by different people. Maybe I misunderstood what they meant or they held genuinely different opinions on the definition. I’m less interested in nailing down one definition, I just find it useful as a tool, although not the only tool.

One component, though, is that there is a learnt component, where you use your experience to better interpret your body’s signals. E. g. my advice to wait a bit just comes from the fact that in my experience there is a delay until you feel satiated.

That includes trying to listen for changes in cravings. E. g. when I am actively training, I tend to crave fried foods less. When I am taking a (seasonal or forced) break from training, those cravings will usually return.

Although you do need to learn a little about what makes for nutritious meals, etc.


One more tip for you.

I struggled with Stages reliability and dropouts for a while on my gen 2. Eventually I found that by using fresh, retail pack, name brand batteries improved the reliability ten fold.

I had been buying 10 packs of whatever cheap batteries off of Amazon. Even oem 10 packs of Energizers were poor performers (maybe they were counterfeit?). Lately I’ve been buying retail pack Duracells and Panasonics and have been having reliable performance.

The retail pack batteries also last twice as long in my Stages so the cost is close to the same.

Other things to check:

Do your zero offset.

Double check the crank length. I’ve heard of situations where people have had mis-matched crank sizes and didn’t realize it for awhile.


@AJS914 good advice on the battery, the stock battery was a Panasonic which seems legit but I grabbed a Duracell to try today.

I think this device is just defective, I developed world tour power on my ride today as the temperature dropped and a bit of rain, the readings of 450 watts at 120 bpm are just entirely unrealistic, so I’ll be contacting the supplier and looking for warranty support


Interesting, glad I spotted this. Probably a conversation for another thread, but yeah we’ve encountered the same limitations with the repeated occlusion protocol & Moxy. Sample rate & SNR seem to be too low for short timeframe, rapid effects like this. Even in lean athletes the smaller interoptode spacing makes it particularly sensitive to local blood volume shifts. Usually not a huge issue, but when we start occluding/releasing cuffs at 250+ mmHg, it plays a role.

For wearable NIRS at the same price point Train.Red (a subsidiary of Artinis) may be an option. It’s basically upgraded Portamon hardware. 10 or 50Hz sample rate, wider interoptode spacing, higher light intensity would all help. Although I haven’t actually tried the repeated occl protocol with Train.Red or Portamon. Only successfully with Oxymon.