Metabolism of Fat at Elevated Heart Rates

I bought a book by Sally Edwards and Sally Reed on using a
heart rate monitor when cycling. They contend that the higher your
heart rate, the lower the amount of fat metabolized and the higher
amount of carbohydrates metabolized.

Don't they have this backwards? I have seen elsewhere that if
you can sustain your heartbeat at 75% of its maximum for twenty
minutes, your body stops metabolizing carbohydrates and starts to
metabolize fat. And that's why you want to get your heart rate up--
to burn off your body fat. Whose right?

Anonymous person wrote:

I have seen elsewhere that if
you can sustain your heartbeat at 75% of its maximum for twenty
minutes, your body stops metabolizing carbohydrates and starts to
metabolize fat. And that's why you want to get your heart rate up--
to burn off your body fat. Whose right?

Well, some of us want to get our heart rates up to become more
aerobically fit, not to get rid of body fat. Nevertheless, here's a
good overview of the science of "fat burning" at various heart rates:

http://www.brianmac.demon.co.uk/fatburn.htm

--
terry morse Palo Alto, CA http://bike.terrymorse.com/

Your name wrote:
|| I bought a book by Sally Edwards and Sally Reed on using a
|| heart rate monitor when cycling. They contend that the higher your
|| heart rate, the lower the amount of fat metabolized and the higher
|| amount of carbohydrates metabolized.
||
|| Don't they have this backwards? I have seen elsewhere that if
|| you can sustain your heartbeat at 75% of its maximum for twenty
|| minutes, your body stops metabolizing carbohydrates and starts to
|| metabolize fat. And that's why you want to get your heart rate up--
|| to burn off your body fat. Whose right?

Why worry about this nonsense. If you just pay attention to intake vs
expediture, your body will take care of the rest. Also, studies have shown
that all things being equal, intense exercise is best for fat loss since you
burn more calories during the exercise period and you burn more for a period
of up to 12 hours afterwards due to increased metabolism.

http://www.exrx.net/FatLoss/HIITvsET.html

http://www.wsu.edu/~strength/intbfatmetab.htm

http://www.wsu.edu/~strength/intbfat.htm

The harder you ride the higher your fat metabolism. But your sugar stores
get burned also. The ratio changes but in the long run what really matters
is if you burn more calories then you consume. So the longer you can ride,
combined with a higher burn rate, will result in more calories comsumed.

Back to the original question of fat metabolism versus effort level:

Your body does not stop using fat storage when you ride hard. In fact is
increases you fat metabolism. But you can only increase that level before
you need to augment it with energy from sugar stores.


Assume your fat metabolism maxes out at around 500 cal/hour. When you are
riding at a moderate effort level, burning about 500 cal/hour, then say 350
is provided through fat metabolism and the rest comes from your sugar
stores. When you are riding very hard, say about 1000 cal/hour, then your
fat metabolism is close to maxed out, say at 500 cal/hour. The other 500
calories per hour come from sugar stores. Your sugar stores are about 1000
calories so you can only ride that hard for about 2 hours before you bonk.

If you ride 4 hours at 500 cal/hour you burn 2,000 calories.
If you ride 2 hours at 1000 cal/hour you burn 2,000 calories.

(all numbers are simplified for clarity of computation. They depend highly
on your body size, fitness, .....)

Bruce

"Your name" wrote in message
...
I bought a book by Sally Edwards and Sally Reed on using a
heart rate monitor when cycling. They contend that the higher your
heart rate, the lower the amount of fat metabolized and the higher
amount of carbohydrates metabolized.

Don't they have this backwards? I have seen elsewhere that if
you can sustain your heartbeat at 75% of its maximum for twenty
minutes, your body stops metabolizing carbohydrates and starts to
metabolize fat. And that's why you want to get your heart rate up--
to burn off your body fat. Whose right?

Bruce Frech wrote:

The harder you ride the higher your fat metabolism.

Fat metabolism increase with heart rate, but only up to a certain
point. Above about 84% of max HR, fat oxidation drops to zero. At
least that's what this source claims:

http://www.brianmac.demon.co.uk/fatburn.htm
--
terry morse Palo Alto, CA http://bike.terrymorse.com/

Your name wrote:

I bought a book by Sally Edwards and Sally Reed on using a
heart rate monitor when cycling. They contend that the higher your
heart rate, the lower the amount of fat metabolized and the higher
amount of carbohydrates metabolized.

Replace the word "amount" with "percentage" and it's correct. The body
cannot metabolise fat quickly enough for high performance and has to use
ATP, glycogen or sugars in preference (ATP is the most immediate,
sugars are slowest of these three).

To burn fat most efficiently you need a 4 hour easy-spinning ride on a
cold winter's day.

Zog The Undeniable wrote:
To burn fat most efficiently you need a 4 hour easy-spinning ride on a
cold winter's day.

I bet you'll burn more fat in a 2 hour all out effort on a warm summers day
or any other day for that matter.
The harder you go the more fat you burn. Period. As others have said you get
to a point where fat isn't sufficient and you also need to use carbs as fuel
but you are still burning plenty of fat.

--
Perre

You have to be smarter than a robot to reply.

Per Elmsäter wrote:
:: Zog The Undeniable wrote:
::: To burn fat most efficiently you need a 4 hour easy-spinning ride
::: on a cold winter's day.
::
:: I bet you'll burn more fat in a 2 hour all out effort on a warm
:: summers day or any other day for that matter.
:: The harder you go the more fat you burn. Period. As others have said
:: you get to a point where fat isn't sufficient and you also need to
:: use carbs as fuel but you are still burning plenty of fat.

It is a mistake to worry about burning fat while you exercise. Forget that.
Just pay attention to intake/outtake. If you create a deficit, you'll lose
fat. Worrying about optimal fat burning just means you'll go easy and you
may burn a greater precentage of fat while you're exercising. But, you'll
also burn fewer calories so the net deficit will be less (provided you
control eating). So you won't lose as much fat.

So, yes, harder is better. And with intervals, you can maximize the total
fat loss.

On Wed, 15 Sep 2004 17:27:26 -0400, "Roger Zoul"
wrote:

Per Elmsäter wrote:
:: Zog The Undeniable wrote:
::: To burn fat most efficiently you need a 4 hour easy-spinning ride
::: on a cold winter's day.
::
:: I bet you'll burn more fat in a 2 hour all out effort on a warm
:: summers day or any other day for that matter.
:: The harder you go the more fat you burn. Period. As others have said
:: you get to a point where fat isn't sufficient and you also need to
:: use carbs as fuel but you are still burning plenty of fat.

It is a mistake to worry about burning fat while you exercise. Forget that.
Just pay attention to intake/outtake. If you create a deficit, you'll lose
fat. Worrying about optimal fat burning just means you'll go easy and you
may burn a greater precentage of fat while you're exercising. But, you'll
also burn fewer calories so the net deficit will be less (provided you
control eating). So you won't lose as much fat.

So, yes, harder is better. And with intervals, you can maximize the total
fat loss.

I agree with Roger. The bike is a very efficient instrument.

Having said that, I found weight loss occurs without much attention to diet
change when you go from riding 30-40 min per day, 7 days a week to 60-70
min per day 7 days a week, or from riding 50-70 miles a week to 100 miles a
week.

I had another weight loss that seemed independent of diet change when I
went from riding 100miles/week to 150-160miles per week -or- 7-8 hrs per
week to about 12-13hrs per week.

Each time the weight loss was about 10lbs.

My rides at the higher distance were at 18-19mph over 20-30miles per ride,
and I rode every day, sometimes twice a day.

So, it takes a significantly higher effort to budge the weight. Part may be
due to adding some muscle (quads and calves are larger).

If you're not careful, you can slowly put the weight back on, even with the
higher mileage - perhaps due to appetite stimulation due to more exercise?

Both times I was not really trying to lose weight as I usually am (I'm
225lbs now), so it was a little bit of a surprise that the weight came off.

So forget small changes in effort and mileage and 'fat burning' zones, and
ambient temperature during your training.

I do think there might be some additional fat loss effect by riding twice a
day, in the am, and again at around 5-6pm - perhaps just b/c you're riding
instead of eating?

So in summary, to lose 10lbs, I had add 50 miles per week (min) or 4-6
additional hours of riding (n=1).

-B

Simply counting calories doesn't work, as the Atkins and South Beach diets have
proven. The ratio of carbs to fats eaten is also important. Carbs that don't
get burned turn into fat, so you need to exercise enough to burn the carbs
that you eat.

At higher heart rates, more fat is burned, but the _ratio_ of carbs burned to
fats burned also goes up. After you "hit the wall" -- i.e., run out of carbs
stored in the muscles, which typically takes 1.5-2 hours -- your ratio of fat to
carbs burned goes back up, but only because your output gets drastically reduced
in total. I've also read that this is a good time to stop, as you start
breaking down muscles to burn their carb content.

On Tue, 14 Sep 2004 22:58:40 -0400, "Roger Zoul" wrote:

Your name wrote:
|| I bought a book by Sally Edwards and Sally Reed on using a
|| heart rate monitor when cycling. They contend that the higher your
|| heart rate, the lower the amount of fat metabolized and the higher
|| amount of carbohydrates metabolized.
||
|| Don't they have this backwards? I have seen elsewhere that if
|| you can sustain your heartbeat at 75% of its maximum for twenty
|| minutes, your body stops metabolizing carbohydrates and starts to
|| metabolize fat. And that's why you want to get your heart rate up--
|| to burn off your body fat. Whose right?

Why worry about this nonsense. If you just pay attention to intake vs
expediture, your body will take care of the rest. Also, studies have shown
that all things being equal, intense exercise is best for fat loss since you
burn more calories during the exercise period and you burn more for a period
of up to 12 hours afterwards due to increased metabolism.

http://www.exrx.net/FatLoss/HIITvsET.html

http://www.wsu.edu/~strength/intbfatmetab.htm

http://www.wsu.edu/~strength/intbfat.htm