calories burned varies more than you might think

zebasschick wrote: »

westrich20940 wrote: »

zebasschick - My Polar actually seemed fairly accurate when it was a lower intensity activity (walking briskly, hiking, or running at a slower consistent pace with not really much elevation change). Once the activity was more intense (running at a faster pace or a route that included elevation changes) it seemed to be an overestimate (sometimes by like 100 or more calories vs. the other sources of info I used). I would simply choose a calorie burn estimate that was a median number of all my data sources and put that into MFP. I lost weight as expected to seems it was more/less accurate in my case.

huh. my old polar - with or without polar beat - gives me a third to a half of the calories MFP and MMF gives me for exercise biking, treadmill and walking up and down stairs. all these get my heart up to a moderate rate.

AnnPT77 wrote: »

westrich20940 wrote: »

Yes, to all of this. I also used ~3 sources of info (Polar HRM, fitness app, and simple Google search) to figure the calories burned of my workouts and put that in MFP manually (Never went with the auto-generated calorie burn for the exercise I was logging).

As far as burning more calories when you were 'in worse shape'....you burn more calories if you are heavier and if your cardio/respiratory fitness isn't great. Once you get more into shape - yes your HR will not go as high (bc you've strengthened your cardo/respiratory fitness) and you will burn less calories (bc you aren't working as hard as you once were and you are smaller).

Sure, body weight makes a difference for activities where we move our bodies through space. Body size isn't a meaningful contributor to the calorie burn for every exercise type, though.

Mostly, the calorie burn (for any activity) is coming from "the work" in the physics sense of work.

Feeling like you're not working as hard is irrelevant: That's pretty much the definition of improved fitness. For cardiovascular exercise specifically, as you get fitter, your stronger heart pumps more blood volume per beat, delivering more oxygen per beat, so your heart rate for the same exercise is lower (and it feels easier, of course). The oxygen consumption has a better correlation with calorie burn, but it's hard to measure oxygen consumption in the everyday context. Heart rate is just a somewhat-adequate proxy.

It's sort of true that people who're skilled at something become more efficient. The variation in efficiency between skilled and unskilled people is narrower or wider for different exercise types. In cycling, the efficiency variation is relatively small, for example.** If same-weight unfit and fit cyclists ride the same bike on the same course at constant weather conditions, and at the same pace/distance, their calorie expenditure will be very close.

(** See, for example: https://citeseerx.ist.psu.edu/viewdoc/download;jsessionid=E292F3073D83BCB1DB240746DA23BE16?doi=10.1.1.469.3228&rep=rep1&type=pdf)

The (well accepted) cycling formula for calories based on watts doesn't include terms for efficiency or body weight. (Body weight may matter indirectly via power production/application, but it's not needed as an explicit term in the formula.)

Note that "less skilled" is not exactly synonymous with "less fit". Efficiency at an exercise is more often about the skill rather than the fitness. Believe me, I've seen very fit people be extremely unskilled (inefficient) rowers. They may have a little general physical-skills advantage over less fit people, but the key variable is still skill at the activity itself. (Even conditioning can be surprisingly sport-specific.)

I strongly suspect the popularity of "fit people burn fewer calories doing the same thing" is out of sync with the general truth of that assertion. In other words, I think the differences are not meaningfully big in a pretty wide range of cases. The personal experience of it feeling easier is persuasive, plus a lot of people think heart rate correlates directly with calorie burn, which is just not true. (That's leaving aside the fact that for many people, the heart rate estimates are relying on an age-based formula for maximum heart rate, and those estimates are inaccurate for a large minority of people, for reasons that have little to do with fitness.)

In at least some of the cases where efficiency matters, the less skilled person wastes motion that doesn't go into our routine ways of measuring the work, such as the measurement by an exercise machine. For me, watching a range of people at the gym using a Concept 2 rowing machine illustrates that pretty clearly: I see unskilled people wasting a lot of energy going for high strokes per minute (among other things), without the technique to accelerate the flywheel through that movement, so the pace/watts/calories seen by the machine are going to be lower than reality. (I don't have a clear idea how much lower, of course, but my guess would be that it could be meaningful: Some of those folks are doing something very intensely aerobic, even though the machine doesn't reflect that movement on its monitor.)

The METS-based process for estimating calories includes body weight explicitly (which is a plus or minus depending on the specific exercise). This approach is also well-accepted and research-based. Some METS values - IMO - lump too-varied things together, and some have been collected in ways that may not capture important variables. What's built into that method is assumption that for a well-specified activity (like running at a specific X miles per hour), relative efficiency between fit and unfit people of the same weight is not an important factor.

I know people here get worried that estimating exercise calories is pretty approximate, so one shouldn't risk it. The usual things that goes with that are that one should use a TDEE calculator (which averages in exercise without even knowing what the exercise is!), or not count exercise calories at all. (Zero is always wrong, but I guess there's a misperception that losing faster is better?).

I think there's also not a lot of appreciation for the range of variability inherent in estimating BMR/RMR, and the fact that the "activity factor" approach used by MFP and TDEE calculators is going to magnify the effect of that variation. It seems like many people mistrust exercise calories (generally a small-ish number in the big picture) and over-trust BMR/RMR + activity factor estimates (generally a big number in the big picture).

It's all estimates all over the place, and some of them are pretty approximate. It can still work.