lower heart rate = higher fat burn? Why did no one tell me??

Himejii

So my Polar H7 came in the mail the other day, I finally got around to checking it out just now. Somewhere in the process, I watched Polar's video about heart rate monitors and what good they do.

Now of course I've heard of "target heart rate" before, and words like "optimal zone" but no one actually spelled out the specific consequences of being, or not being, in that zone. I mean, it seemed intuitive to me: "work harder, burn more energy." And that's not false, it's simple physics.

But where the physics stops and the biology begins, is with the source of that energy being burned. According to Polar's little video, the whole point of the target zone is that when you go above it, you start to shift the carbs vs fat burning ratio towards the carbs end. Which makes sense, since carbs are readily available energy and therefore easily accessible when you need it NOW like at the peak of your workout.

Now I'm sure that to 95% of you fitness buffs, this is totally old news. But the infographic spelled it out so clearly, and I guess just made it *click*

So that's a relief. I mean, it's much much easier to work below my maximum output, that's for darn sure! I could probably work out twice as long if I was going 20% less intense, and that would be great!

blackcoffeeandcherrypie

I think this only matters if carbs are available to your system. I don't like to eat before I work out because it makes me feel sluggish and I'm always hungry again afterwards anyway. So if there are no carbs, I think the body uses stored glycogen until that runs out and then it is forced to convert fats for energy anyway.

_Zardoz_

It's actually right but wrong. The Fat Burning Zone' yes it does exists the theory is at lower aerobic threshold the body burns more fat (at around 50% of it's calories from fat) at higher intensities only around 35% of the calories will be from fat. So it makes sense doesn't it you should be at the lower intensity? Actually no because at higher intensities your overall calorie burn will be much higher so 35% of calories at a higher threshold will actually be more calories than 50% at a lower intensity. Hope that makes sense.
So if you need to work at a lower aerobic threshold that's fine but don't do it just because you think you'll be burning more fat because you wont. If I'd only run in the fat burning zone for my running from the start I'd still be running 15 minute miles. Some of the problem is that 'the fat burning zone' has almost entered mythical status. Polar themselves haven't helped who seem to push it in a lot of their literature.

yirara

It's actually right but wrong. The Fat Burning Zone' yes it does exists the theory is at lower aerobic threshold the body burns more fat (at around 50% of it's calories from fat) at higher intensities only around 35% of the calories will be from fat. So it makes sense doesn't it you should be at the lower intensity? Actually no because at higher intensities your overall calorie burn will be much higher so 35% of calories at a higher threshold will actually be more calories than 50% at a lower intensity. Hope that makes sense.
So if you need to work at a lower aerobic threshold that's fine but don't do it just because you think you'll be burning more fat because you wont. If I'd only run in the fat burning zone for my running from the start I'd still be running 15 minute miles. Some of the problem is that 'the fat burning zone' has almost entered mythical status. Polar themselves haven't helped who seem to push it in a lot of their literature.

Quoted for truth!

Plus you'd need to know your maximum heart rate to calculate a certain percentage for some training zone or another. Just taking lists you find online might be completely off. For example, my max is at about 205. 70% of that is 144, yet those calculators tell me I should certainly not get over 130. My heartrate goes over that by just looking at an elliptical.

LiftAndBalance

It's actually right but wrong. The Fat Burning Zone' yes it does exists the theory is at lower aerobic threshold the body burns more fat (at around 50% of it's calories from fat) at higher intensities only around 35% of the calories will be from fat. So it makes sense doesn't it you should be at the lower intensity? Actually no because at higher intensities your overall calorie burn will be much higher so 35% of calories at a higher threshold will actually be more calories than 50% at a lower intensity. Hope that makes sense.
So if you need to work at a lower aerobic threshold that's fine but don't do it just because you think you'll be burning more fat because you wont. If I'd only run in the fat burning zone for my running from the start I'd still be running 15 minute miles. Some of the problem is that 'the fat burning zone' has almost entered mythical status. Polar themselves haven't helped who seem to push it in a lot of their literature.

Quoted for truth!

Plus you'd need to know your maximum heart rate to calculate a certain percentage for some training zone or another. Just taking lists you find online might be completely off. For example, my max is at about 205. 70% of that is 144, yet those calculators tell me I should certainly not get over 130. My heartrate goes over that by just looking at an elliptical.

All of this!

Plus: As far as I understand it, your body will always use carbs/glycogen before fat because it's much easier for the body to burn. So if you start out with a low effort and keep to that, your body might never actually go beyond using up its glycogen stores. Then you'll have burned less overall calories AND less fat. I would think, then, that the only useful scenario for lower intensity steady-state cardio is at the end of a high intensity workout. That way you'll already be pretty much out of glycogen stores and won't have the energy for even more high intensity anyways so you could add some low intensity to maximise fat burn. Hope that makes sense.

donnam40

All of the above. Another reason the fat-burning zone is not effective in the long run is because it does not take into account your "afterburn". A high intensity workout will give a higher overall burn as your metabolism will stay elevated for a period of time after you finish working out, effectively burning more calories while you are not working out.

Your workouts should consist of both easy, moderate and hard workouts. You need the easy ones because it is not good for you to train at high intensity 100% of the time. The high intensity workouts will help you improve your fitness quicker and the moderate workouts give you a good balance.

Donna

Himejii

Thank you everyone, for clearing that up.

Also, what you said all seems much more intuitive and in-line with what I'd always thought myself. Not sure what Polar, or anyone else for that matter, has to gain from spreading misinformation... I guess the idea that you need a HRM to stay "in the zone" but you can work at your maximum output (or near-max) just by going as hard as you can without falling over.

LiftAndBalance

I suppose it also has a lot to do with an assumption of people's laziness - who wouldn't love for less effort to give the best results? :bigsmile: I was actually surprised you hadn't heard that before since it's such a common assumption (we even learned it in school! :noway: )