Efficient Fat Burning

What does it mean, exactly, when the body is said to become more
efficient at burning fat?

Does it mean that the body burns more fat or less fat?

"Efficient" could mean "less fat" in the same way that fuel efficiency
in cars means *less* fuel used for the same distance. Thus, the more
"efficient" our bodies become at using fat, the more intense our
workouts have to be to burn the same amount as before!

But that's semantics...what's the actual physiology??

On Jan 21, 11:54*pm, Prisoner at War
wrote:
What does it mean, exactly, when the body is said to become more
efficient at burning fat?

Does it mean that the body burns more fat or less fat?

"Efficient" could mean "less fat" in the same way that fuel efficiency
in cars means *less* fuel used for the same distance. *Thus, the more
"efficient" our bodies become at using fat, the more intense our
workouts have to be to burn the same amount as before!

But that's semantics...what's the actual physiology??

Yes.

"Prisoner at War" wrote in message
...

What does it mean, exactly, when the body is said to become more
efficient at burning fat?

Does it mean that the body burns more fat or less fat?

"Efficient" could mean "less fat" in the same way that fuel efficiency
in cars means *less* fuel used for the same distance. Thus, the more
"efficient" our bodies become at using fat, the more intense our
workouts have to be to burn the same amount as before!

But that's semantics...what's the actual physiology??

For the physiology, I think Gary Taubes' "Good Calories, Bad Calories" may
help.

The phrase seems ambiguous to me, thus, might need contextual clarification.

On Jan 22, 11:36 am, "Cubit" wrote:


For the physiology, I think Gary Taubes' "Good Calories, Bad Calories" may
help.

The phrase seems ambiguous to me, thus, might need contextual clarification.

Indeed! But it's such a popular sentiment, and when I just read it
again in "Runner's World Complete Book of Running" I just had to ask
and find out, once and for all...the usual context appears to suggest
that our bodies burn more fat as it becomes more "efficient," though
I've also read somewhere (Noakes?) that being more efficient means
that less calories are burned for the same work....

On Jan 22, 9:06*am, Prisoner at War wrote:
On Jan 22, 11:36 am, "Cubit" wrote:



For the physiology, I think Gary Taubes' "Good Calories, Bad Calories" may
help.

The phrase seems ambiguous to me, thus, might need contextual clarification.

Indeed! *But it's such a popular sentiment, and when I just read it
again in "Runner's World Complete Book of Running" I just had to ask
and find out, once and for all...the usual context appears to suggest
that our bodies burn more fat as it becomes more "efficient," though
I've also read somewhere (Noakes?) that being more efficient means
that less calories are burned for the same work....

In trained long-distance runners, the working muscles rely on a
greater proportion of their energy from fat for a given effort level
(the fat/glucose mixture is richer, so to speak). They can run on
mostly fat at paces that require the less trained runner to burn
mostly glucose. This gives them a higher lactate threshold so they can
run faster without accumulating lactic acid. If you can run at a 5:00
mile pace (or better!) without lactic acid buildup, because you're
doing it on fat, then you can kick some serious ass in distance
running. Kicking serious ass makes you inefficient in terms of total
energy use. We can say that these trained athletes are efficient in
their use of glycogen relative to their power output and speed.

The other sense of efficiency, less calories burned for the same work,
comes from biomechanics and from maintaining a low body mass. In
racing a given distance, the intensity of your energy output (your
wattage, so to speak) is capped. If you go too fast too early, you
will blow up. So you have to produce the greatest performance (fastest
forward motion) on a fixed energy output. So yes, that kind of
efficiency is directly related to being competitive.

Efficient use of glycogen means your muscles can produce a high power
output and sustain it, and turning that into the best possible
performance means making the most efficient use of that power: not
wasting it on useless motions, or carrying extra mass.

But all of that has little to do with losing body fat. During steady
endurance work, your muscles burn intra-muscular fat, plus free fatty
acids. Free fatty acids are released from adipose tissue when you're
not exercising. Like for instance when you are sleeping. Or during the
recovery periods in interval training. Eating breakfast sends these
morning free fatty acids scurrying back into storage, which is why it
might be a good idea to exercise first.

"Prisoner at War" wrote in message
...

What does it mean, exactly, when the body is said to become more
efficient at burning fat?

Does it mean that the body burns more fat or less fat?

Without context, it's difficult to know, but it seems a poor choice of
wording.

During aerobic exercise, it is *more* efficient to burn *more* fat because
that means that you're burning less glycogen, and glycogen is much more
scarce than fat (you only have ~400gm of it and that only provides as much
energy as about 200gm fat)

This is fairly basic stuff -- any book on exercise physiology or endurance
training will discuss it.

Cheers,
--
Elflord

Dnia 2008-01-22 Elflord napisa³(a):
"Prisoner at War" wrote in message
...

What does it mean, exactly, when the body is said to become more
efficient at burning fat?

Does it mean that the body burns more fat or less fat?

Without context, it's difficult to know, but it seems a poor choice of
wording.

During aerobic exercise, it is *more* efficient to burn *more* fat because
that means that you're burning less glycogen, and glycogen is much more
scarce than fat (you only have ~400gm of it and that only provides as much
energy as about 200gm fat)

That would be liver alone, AFAIR. Most of glycogen is stored in muscles
and it takes a while to burn it all. I remember reading about glycogen
depletion workouts (recent fad in some sport related training regimes)
and it took quite an effort to burn it all, plus some fasting too.

Fat isn't good fuel source for aerobic workouts, because it needs more
oxygen to use it. IOW you get winded more easily and overall intensity
must go down (a lot).

This is fairly basic stuff -- any book on exercise physiology or endurance
training will discuss it.

I'm missing context too, so it could be that I write about unrelated
topic. Anyway, we have more than 400mg of glycogen and fat is bad fuel
for intense aerobic activity. Your body will use it, if it has no
choice, but your training will be lousy.

--
Andrzej Rosa 1127R

On 2008-01-22, Andrzej Rosa wrote:

During aerobic exercise, it is *more* efficient to burn *more* fat because
that means that you're burning less glycogen, and glycogen is much more
scarce than fat (you only have ~400gm of it and that only provides as much
energy as about 200gm fat)

That would be liver alone, AFAIR. Most of glycogen is stored in muscles
and it takes a while to burn it all.

I don't think so. We enough to cover about 2hrs of hard running -- that's
a bit over 2000 calories. That's where the "hitting the wall" theory came
from -- you don't have enough glycogen to run a marathon without using some
fat.

I remember reading about glycogen
depletion workouts (recent fad in some sport related training regimes)
and it took quite an effort to burn it all, plus some fasting too.

Fat isn't good fuel source for aerobic workouts, because it needs more
oxygen to use it.

Without qualification, it's hard to say whether it's a "good" fuel source for
aerobic workouts.

It's "good" in the sense that it's abundant, but "bad" in the sense that it
doesn't provide energy as quickly.

Any kind of speed work depends heavily on glycogen stores, because intensity
is key.

But at least for longer events (e.g. 2hrs+), it is advantageous to be able to
metabolise fat as quickly as possible, because fat is abundant whereas glycogen
is not.

IOW you get winded more easily and overall intensity
must go down (a lot).

This is fairly basic stuff -- any book on exercise physiology or endurance
training will discuss it.

I'm missing context too, so it could be that I write about unrelated
topic. Anyway, we have more than 400mg of glycogen and fat is bad fuel
for intense aerobic activity. Your body will use it, if it has no

If you're doing the exercise for any purpose besides competing in endurance
events, I'd agree.

People competing in endurance events can and should do base training to address
this.

Cheers,
--
Elflord

Dnia 2008-01-22 Elflord napisa³(a):
On 2008-01-22, Andrzej Rosa wrote:

That would be liver alone, AFAIR. Most of glycogen is stored in muscles
and it takes a while to burn it all.

I don't think so. We enough to cover about 2hrs of hard running -- that's
a bit over 2000 calories. That's where the "hitting the wall" theory came
from -- you don't have enough glycogen to run a marathon without using some
fat.

That 2 hours of hard running rings true, so it may be that I mixed the
numbers (that is miligrams with calories).

[...]
I'm missing context too, so it could be that I write about unrelated
topic. Anyway, we have more than 400mg of glycogen and fat is bad fuel
for intense aerobic activity. Your body will use it, if it has no

If you're doing the exercise for any purpose besides competing in endurance
events, I'd agree.

And endurance events, which take more than 2000 cal to finish. Most of
them is way shorter. Even ten miles run should be safely within the
limits of our glycogen stores.

[...]
--
Andrzej Rosa 1127R

On Jan 22, 12:02*pm, Elflord wrote:
"Prisoner at War" wrote in message
...

What does it mean, exactly, when the body is said to become more
efficient at burning fat?

Does it mean that the body burns more fat or less fat?

Without context, it's difficult to know, but it seems a poor choice of
wording.

During aerobic exercise, it is *more* efficient to burn *more* fat because
that means that you're burning less glycogen, and glycogen is much more
scarce than fat (you only have ~400gm of it and that only provides as much
energy as about 200gm fat)

That's different. The desired result during this type of sport is (for
instance) to go the farthest in the least amount of time, not to lose
the most adipose fat with the least effort.

You can't discuss the efficiency of a process without knowing what the
important result that that process must yield, and what input
resources are to be optimized.