Interesting Factoid # 228

On Sat, 15 Dec 2007 06:51:09 -0800, Prisoner at War wrote:


"During exercise, your muscles use a metabolic priority system for
generation of energy. This is particularly true during aerobic
exercise. First, carbohydrate is used, then fat, then protein.
Because of the tremendous stress that resistance training puts on the
muscles, the metabolic priority system gets ignored. When cortisol is
released, it causes a breakdown of protein, carbohydrate, and fat...."

-- from "Nutrient Timing" (2004)


Implications:

Cardio is the best for burning fat, best for weight-loss, given that
carbs and fats are utilized first. (Protein isn't tapped as a
resource until about an hour of cardio, according to another passage
in the book.) This debunks the myth propagated in weight-lifting
circles that even a resistance-exclusive program can promote weight
loss.

Remaining Questions:

How, exactly, does this metabolic priority system get thrown off track
by the intense conditions created by serious weight-lifting?


The "metabolic priority system" does not get thrown off track by
resistance training. Lifting weights is, by its nature, a short duration,
anaerobic activity. Even very "intense" resistance training is
characterized by relatively short bouts of high intensity activity
followed by a recovery period. As a result, it uses anaerobic energy
systems, which only 'burn' carbohydrates.

The idea that resistance training on its own can lead to reductions in
body fat is not entirely false. Muscle is primarily where fats gets
'burned'. Adding muscle will increase a person's metabolic rate. And,
resistance training burns calories, where ever they may come from, thus
helping to eliminate excess calories. So, it is possible to loose fat by
lifting weights. But, it is not necessarily the most effective way to
reduce body fat.

On Mon, 17 Dec 2007 07:58:47 -0800, Prisoner at War wrote:

On Dec 16, 8:02 pm, Shava_X wrote:


The "metabolic priority system" does not get thrown off track by
resistance training.

But he said it did -- the author is the longtime chairman of
kinesiology at Texas University, and an actual researcher in this
field, too!

Lifting weights is, by its nature, a short duration,
anaerobic activity. Even very "intense" resistance training is
characterized by relatively short bouts of high intensity activity
followed by a recovery period. As a result, it uses anaerobic energy
systems, which only 'burn' carbohydrates.

Well, that's precisely what I was wondering! What's the mechanism
whereby protein is burned for fuel -- and why should it be tapped
first during anaerobic activity but last during aerobic activity?

I'm just reading his book all over again now, having forgotten a lot
of the details, so maybe he covers it later on...but it's not
something that seems immediately sensible, that a "metabolic priority
system" should get screwed up by one kind of physical effort but not
another.

The idea that resistance training on its own can lead to reductions in
body fat is not entirely false. Muscle is primarily where fats gets
'burned'. Adding muscle will increase a person's metabolic rate. And,
resistance training burns calories, where ever they may come from, thus
helping to eliminate excess calories. So, it is possible to loose fat by
lifting weights. But, it is not necessarily the most effective way to
reduce body fat.

All true -- this is what makes so-called "spot shaping" possible (not
spot reducing, mind you, but spot shaping). But I've actually heard
it said that cardio is not necessary at all if you lift intensely, so
I just wanted to put to rest that myth.


If that is what the author put, then the author is just plain wrong.
given His credentials, i can only speculate that He was trying to simplify
things and did a poor job.

The mechanism my which protein is tapped for fuel is call gluconeogenesis.
It is the process whereby protein is turned into glucose. It is not very
efficient, and that is why protein is tapped as a fuel source *Last*.