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Generally speaking, by running slower you burn a higher percentage of calories from fat. The trade-off is you don't cover as many miles in an hour, so you burn fewer calories overall in a given time. Speed and body weight also have some effect on the number of calories burned (see the article at the first link below). BMI and fitness level don't have any effect on heart rate zones, according to the experts. Though as you gain fitness you should find it easier to run in a particular zone, and you'll probably be faster in that zone. The second article below is a good guide to using a heart rate monitor and determining your training zones. It has a calculator for zones based on what you determine is your resting heart rate and your maximum heart rate. Maximum is the hard part. There are several formulas but none are accurate for everyone and some only work for about 50% of the population. Have fun!
(How many calories are you really burning?)
(Heart Monitor Training)
however, the articles do not appear to focus on my question (calories from fat, not calories in general or training zone in general). The second paper, though, sort of acknowledges that fitness status (as partially represented by resting heart rate) has some influence. I'm probably after something slightly more "scientific" than that.
Thanks anyway, it was an interesting read...
WOW Laura that was a heck of an answer!!
I've skimmed the paper you suggested and looks like what I was after: some science, just not too much of it. I'll need to read it more carefully later.
Meanwhile, I tried the website you mentioned. It's pretty cool! I got my chart and as I see I have to keep my heart rate lower than I thought to stay close to the peak of fat burning. I don't have a garmin, just a cheap HR monitor, but that I see I'm missing a lot of stuff! Being a bit of a control freak, I need one now .
As I understand, the chart is based on my actual biometrics, so if my body changes through training (like, my HRMax or HRR changes) I'll just update my values and I'll get a new chart (I tried that with some overly optimistic prediction ).
Well, can't thank you enough!
Why are you trying to burn more fat? Are you trying to improve your body's ability to use fat as fuel in long races like marathons or ultramarathons? Or are you just trying to lose weight?
If you are trying to lose weight, it's doesn't really matter whether you are burning fat or gylcogen. In fact, the faster you run, the more calories you will burn, but the higher the percentage of them will be from glycogen vs. fat.
Weight loss results from burning more calories than you consume. Your body doesn't care whether you burn calories from fat or glycogen during your workout or not.
Recent studies have shown that if you run fast enough, you continue to burn calories at an elevated rate, long after your workout is over.
Here's a blog post that I wrote about it:
Boston Marathon Finisher
sorry, I don't really agree when you say "If you are trying to lose weight, it's doesn't really matter whether you are burning fat or gylcogen.".
it is one thing to lose weight; it is one thing to shape up and lose fat.
gylcogen is stored in muscles and present in very limited quantity in our body. after we burn gylcogen, we eat carbs because we want to restore our gylcogen. we need gylcogen to run fast.
on the other hand, for most people, fat accounts for a significant % of body weight. if you burn fat you get fitter.
note that I'm not saying I never want to run fast, it's just that I'm also interested in burning fat.
I'm aware of EPOC and stuff, and once again, I've read contradictory claims about how much fat is burnt as part of EPOC. The paper you quote is only about young men, is not freely available, and you didn't provide a reference for the "other research studies". Do you have a reference? Maybe something we can actually read?
I did some googling, of course. For instance, here:
I get that for young women the difference in fat burnt because of EPOC is not really significant over 24h for 50% vs 72% vo2max. however, I don't have access to this publication or the one you quoted, I can only read the abstract.
Perhaps Laura could help me here too!
To lose bodyfat, you have to create a calorie deficit. You have to burn more calories than you are taking in. If you run slowly, you will burn a higher percentage of fat vs. carboydrates, but you will burn a much smaller total amount of calories. If you run faster, you will burn more calories and your body will have to burn fat to replace your glycogen stores.
If you run at a slow pace that maximizes fat burning, it will take you much longer to lose your bodyfat, because the rate at which you are burning calories is much lower.
Here are some links the other studies that I referenced.
Working out at 50% of VO2max produces no calorie afterburn.
Increasing fat burning has no effect on bodyfat
Fat oxidation doesn't results in weight loss, calorie deficit does
Boston Marathon Finisher