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Power meter and calorie counting?

Old 10-31-19, 08:23 AM
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Power meter and calorie counting?

I've been idly shopping for a power meter. I'm curious other than doing the math independently, do any of the popular calorie counting apps (like say My Fitness Pal) receive and use the power data to calculate calories burned? I haven't used it in a while, so maybe it's more clever now, but it used to get time and distance from Strava and shunt the workout into a bracket by speed - no accounting for type of bike, type of terrain, or elevation.
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Old 10-31-19, 09:23 AM
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Not sure what fields myfitnesspal pulls, anytime I've used it, it's been manual entries and I've just used the kj metric from my ride file, which is approximately equivalent to calories burned
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Old 10-31-19, 09:59 AM
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All these apps seem pretty well connected. MyFitnessPal takes Calories from Garmin Connect. If you have a powermeter Garmin uses kJ for Calories. Once you connect Garmin to Myfitness the transfer is automatic.
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Old 10-31-19, 10:26 AM
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There is a lot of metabolism going on between the calories in the food you eat and the output energy of your legs. You also don't measure any core and upper body and heart and lungs energy.

With other words, depending an all the digestion and metabolism inefficiencies and auxiliary needs you could put out 500 calories out of your legs, but that may mean 2,000 calories eaten. Or 1,000, or 3,000.
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Old 10-31-19, 12:36 PM
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Originally Posted by gregf83 View Post
All these apps seem pretty well connected. MyFitnessPal takes Calories from Garmin Connect. If you have a powermeter Garmin uses kJ for Calories. Once you connect Garmin to Myfitness the transfer is automatic.
This is how I've done it. It "just works" with no monkeying around on my part.
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Old 10-31-19, 12:39 PM
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Originally Posted by HerrKaLeun View Post
There is a lot of metabolism going on between the calories in the food you eat and the output energy of your legs. You also don't measure any core and upper body and heart and lungs energy.

With other words, depending an all the digestion and metabolism inefficiencies and auxiliary needs you could put out 500 calories out of your legs, but that may mean 2,000 calories eaten. Or 1,000, or 3,000.
There has been a tremendous amount of research on this. Riding a road bike, there isn't much difference between any two humans in terms of metabolic efficiency. That's not true with a lot of exercise, but in cycling, you just don't have the opportunity to waste much energy that can't be accounted for. You clip your feet into pedals and turn them in circles, always the same size. A power meter measures physical work done, and "converting" that to calories burned has a maximum error of about 5%. If your power meter says you burned 500 kCal, the truth might be anywhere from 487 to 513 kCal. The +/- is like 1/4 of an oreo.
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Old 10-31-19, 01:06 PM
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Originally Posted by HerrKaLeun View Post
There is a lot of metabolism going on between the calories in the food you eat and the output energy of your legs. You also don't measure any core and upper body and heart and lungs energy.

With other words, depending an all the digestion and metabolism inefficiencies and auxiliary needs you could put out 500 calories out of your legs, but that may mean 2,000 calories eaten. Or 1,000, or 3,000.
There are some small differences in how one metabolizes different types of food but these are 2nd and 3rd order effects that don't really explain why people gain or lose weight. The majority of Americans just eat too much by a significant amount.

My experience has been that over a period of weeks/months if I carefully count Calories in and out that the resulting weight loss is very close to predicted. It doesn't work very well at the daily level as changing the sodium intake will result in large weight swings due to water retention but these cancel out over time.
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Old 10-31-19, 01:56 PM
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Originally Posted by Seattle Forrest View Post
There has been a tremendous amount of research on this. Riding a road bike, there isn't much difference between any two humans in terms of metabolic efficiency. That's not true with a lot of exercise, but in cycling, you just don't have the opportunity to waste much energy that can't be accounted for. You clip your feet into pedals and turn them in circles, always the same size. A power meter measures physical work done, and "converting" that to calories burned has a maximum error of about 5%. If your power meter says you burned 500 kCal, the truth might be anywhere from 487 to 513 kCal. The +/- is like 1/4 of an oreo.
I've read that the "engine" is about 25% efficient. Luckily, the ratio of kj to kcal is about 4 so whatever work output your PM shows you can just change the unit from kj to kcal and you're done. Easy peasy.
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Old 11-01-19, 10:29 AM
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I suspect that, for most people, using a power meter as part of a weight loss plan is a chance to play with a new toy. Racers and long distance tourists might be the exception, as they're likely trying not to lose too much, too fast. If you just link power meter output and additional food input, you'll gain weight.

Far better to spend that time planning meals, and cooking real food, and figuring out how to avoid grabbing random junk food and stuffing your face when you're bored. That business of eating 500-1,000 calories a day less than your body needs to maintain its current weight? Old-fashioned, tired, not much fun; oh, and it works.
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Old 11-01-19, 11:00 AM
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Originally Posted by pdlamb View Post
I suspect that, for most people, using a power meter as part of a weight loss plan is a chance to play with a new toy. Racers and long distance tourists might be the exception, as they're likely trying not to lose too much, too fast. If you just link power meter output and additional food input, you'll gain weight.

Far better to spend that time planning meals, and cooking real food, and figuring out how to avoid grabbing random junk food and stuffing your face when you're bored. That business of eating 500-1,000 calories a day less than your body needs to maintain its current weight? Old-fashioned, tired, not much fun; oh, and it works.
I'd say that linking PM data to calorie burn is not about additional food input, the opposite actually. A PM gives a more realistic(lower) estimate of calorie burn on the bike compared to HR or software based guesses which are often wildly high
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Old 11-01-19, 12:06 PM
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Originally Posted by redlude97 View Post
I'd say that linking PM data to calorie burn is not about additional food input, the opposite actually. A PM gives a more realistic(lower) estimate of calorie burn on the bike compared to HR or software based guesses which are often wildly high
Well, the best success I've had losing weight involves calculating baseline metabolism (based on body weight), ignoring calories burned off through exercise, and basing my caloric intake on that (less 500 calories a day). Adding in any kind of exercise allowance reduced the weight loss, as you might expect. No need for PM, HR or software based guesses (although I agree some of those are ridiculously high).
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Old 11-01-19, 12:08 PM
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Thanks everyone
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Old 11-01-19, 12:26 PM
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Originally Posted by pdlamb View Post
Well, the best success I've had losing weight involves calculating baseline metabolism (based on body weight), ignoring calories burned off through exercise, and basing my caloric intake on that (less 500 calories a day). Adding in any kind of exercise allowance reduced the weight loss, as you might expect. No need for PM, HR or software based guesses (although I agree some of those are ridiculously high).
How do you address that with say a 5 hour 2000+cal ride? At some point ignoring calories on the bike especially if you are trying to balance weight loss with power gains having a whole picture of your caloric needs is better
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Old 11-01-19, 12:36 PM
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Yeah, I don't understand how ignoring additional, reliable data is better.
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Old 11-01-19, 12:53 PM
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You don't have to choose between using a power meter and eating well. Looking at a single data point from the summary of a ride doesn't take any time away from preparing quality food.

If you're riding 20 miles a week it's not going to hurt anything to ignore that, but at some point undereating has real consequences for your energy and fitness levels, and your overall health.
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Old 11-01-19, 01:01 PM
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Originally Posted by pdlamb View Post
Well, the best success I've had losing weight involves calculating baseline metabolism (based on body weight), ignoring calories burned off through exercise, and basing my caloric intake on that (less 500 calories a day). Adding in any kind of exercise allowance reduced the weight loss, as you might expect. No need for PM, HR or software based guesses (although I agree some of those are ridiculously high).
For me, maintaining weight is important but not as important as power output. Given the choice, I'll take watts over weight loss any day of the week, even if watts/kg dips a little, within reason.

When I'm going through high intensity training blocks, I don't count calories for the most part. My goal during these periods is to maintain weight. A couple pounds +/- isn't a big deal. The goal is not to hinder the performance improvement by underfueling.

Then there are times in the year that I dedicate to weight loss. Long, low intensity rides where I'm mostly burning fat. No insulin spike when I get home, so I can just go about my day as if I hadn't ridden at all. Easy 1500 kCal caloric deficit for that day.
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Old 11-01-19, 02:33 PM
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Originally Posted by pdlamb View Post
I suspect that, for most people, using a power meter as part of a weight loss plan is a chance to play with a new toy. Racers and long distance tourists might be the exception, as they're likely trying not to lose too much, too fast. If you just link power meter output and additional food input, you'll gain weight.

Far better to spend that time planning meals, and cooking real food, and figuring out how to avoid grabbing random junk food and stuffing your face when you're bored. That business of eating 500-1,000 calories a day less than your body needs to maintain its current weight? Old-fashioned, tired, not much fun; oh, and it works.
How do you know what you need to maintain your current weight if you don't know how much you burn?

FWIW, in 2010 I weighed 325 lbs. In 2013 I weighed 165 lbs. Today I weigh 165 lbs. Power meter is a great way to get quantifiable data on how much you're burning. Food tracking apps are a great way to get quantifiable data on how many calories you are putting into the system. Think of it as trying to make a budget if you only know your income but not your expenses.

To the OP - most apps will use power meter data to give you a reasonably accurate estimate of calories burned on the bike - FAR more accurate than the estimates they give without PM data.
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Old 11-01-19, 05:57 PM
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I'm curious how all the people before "civilization" maintained their weight and avoided all the civilisation diseases (e.g. heart, diabetes,) without having power meters, calorie counters or any knowledge of metabolism? Same with animals in the wild.
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Old 11-01-19, 06:53 PM
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… by dying before 30, often of starvation.
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Old 11-01-19, 07:45 PM
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Originally Posted by pdlamb View Post
Well, the best success I've had losing weight involves calculating baseline metabolism (based on body weight), ignoring calories burned off through exercise, and basing my caloric intake on that (less 500 calories a day). Adding in any kind of exercise allowance reduced the weight loss, as you might expect. No need for PM, HR or software based guesses (although I agree some of those are ridiculously high).
Every day this week I've burned an extra 1400+ Cals/day from commuting. Using your approach I'd be running a deficit of 1900 Cals/day. I don't think I could manage that.

For me, adding an extra 1000+ Cals/Day of consistent exercise makes it much easier to maintain a 500 Cal/day deficit. I can even have a beer or two which is difficult to do without exercise. Of course you can do it but you end up sacrificing nutrition.
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Old 11-02-19, 01:33 PM
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Originally Posted by caloso View Post
Yeah, I don't understand how ignoring additional, reliable data is better.
Data <> Information, despite what you might hear today. Data (e.g., I burned 700 calories riding today) is pretty meaningless. Information (e.g., my energy balance of calories consumed vs. burned today) is useful.

Remember how Lance Armstrong famously weighed everything he ate? Do you do that? (I don't.) Research has shown that most people underestimate what they eat, and overestimate how much they burn. Even if you figure out (to within 10%) how much you burn on your bike, consider that people who exercise generally depress their basal metabolism the rest of the day; so 1,000 calories burned on the bike doesn't mean an automatic 1,000 calories less burned in 24 hours.

For a full picture (information, as above), you'd need to live in a metabolic measurement chamber. Or check your weight regularly and compare weight today to a month ago, or a month from now. A good scale is cheaper than a power meter, and gives better information over the long term.
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Old 11-02-19, 01:42 PM
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Originally Posted by gregf83 View Post
Every day this week I've burned an extra 1400+ Cals/day from commuting. Using your approach I'd be running a deficit of 1900 Cals/day. I don't think I could manage that.

For me, adding an extra 1000+ Cals/Day of consistent exercise makes it much easier to maintain a 500 Cal/day deficit. I can even have a beer or two which is difficult to do without exercise. Of course you can do it but you end up sacrificing nutrition.
First, thanks for validating my idea that the impetus for this thread was to estimate how much more can be eaten.

Second, congratulations on your commuting. You must burn twice as much as I do on my 20 mile round trip. I consistently come up with about 700 calories/day on the power meter when I commute; of course, the old 3 miles = 100 calories rule of thumb gives me similar results.

Third, I agree with you that running a 1,900 calorie a day deficit isn't sustainable. I tried something similar for the first month and a half on my cross country tour. Lost weight, but I was miserable and not very pleasant, I fear. Giving up an avoiding sugar, and adding a dessert every day, and I enjoyed the rest of the trip much more.

However, I'll argue that your 1,400 calories per day commute is substantially longer or harder than most bike commuters (check the bike commuter forum for examples). I think my initial post had that covered, you're obviously not "most people."
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Old 11-02-19, 09:21 PM
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I don't think most bike commuters are reading the training forum either.

Personally I don't commute at all, I'm lucky enough to work from home. But I enjoy long rides, where I cover a lot of ground and see different neighborhoods and backgrounds. 1,100 kJ in a day is typical for me (except during time of injury) between lunch and after work rides. I don't think @gregf83 is very unusual among people in this forum.
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Old 11-03-19, 10:38 AM
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Originally Posted by pdlamb View Post

Remember how Lance Armstrong famously weighed everything he ate? Do you do that? (I don't.) Research has shown that most people underestimate what they eat, and overestimate how much they burn. Even if you figure out (to within 10%) how much you burn on your bike, consider that people who exercise generally depress their basal metabolism the rest of the day; so 1,000 calories burned on the bike doesn't mean an automatic 1,000 calories less burned in 24 hours.
I spent a good deal of this past year in weight loss mode, calorie deficit. I weighed or measured almost everything for the first 4 months. Now I do it when I recognize my portion sizes increasing, or feel I've lost my "calibrated eye"... I did have weight loss surgery a year ago. So weights and measures were important to keep from ripping stitches... But also to keep me in deficit but get my nutrients. Yes, I use supplements. Down over 110 pounds feels good. Now I've added a smart trainer, so I can see power output in relation to heart rate and energy expended. Of course, it doesn't hurt that now and again I tend to be a data nerd...
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Old 11-03-19, 11:29 AM
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So you commute about 20mi each way to work at about 200w avg (including coasting)?

That would be 1400 per day.

Meaning you’re commuting both ways at probably over 220w NP. Unless you’re a cat 1 racer in zone 1 the whole time you’d be showering twice a day from that.

That doesn’t seem right.
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