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[Bill Phillips - the new kingpin of exercise physiology.]

In misc.fitness.misc Andrew Stranz <andrewst@home.com> wrote:
: Larry,
: I agree that you are burning fat all the time, but in the beginning, it
: will be at a much lower level than after approximately 20 minutes

The changing RER (respiratory exchange ratio) - the measure of the ratio of
carbohydrate to fat utilized during activity - does suggest that fat 
utilization increases as exercise continues at steady state.

However, it's not an "on/off" thing that occurs at 20 minutes, as it is
commonly misrepresented.  Moreover, this is only valid for *STEADY-STATE*
exercise - once you start messing around with intensity at all the process
of readjustment to the new exercise level begins all over again (this
would include adjusting the grade or speed of the treadmill, going up a
"hill" on the stairclimber, etc.).

Moreover, factors besides ratio of fuels burned affects RER.  For example,
increasing reliance on anaerobic energy systems will decrease blood pH.
One of the principal means of pH buffering (the bicarbonate system), will
help buffer the pH changes, but will do so by taking up the excess hydrogen
ions (combing them with bicarbonate to form carbonic acid).  The 
carbonic acid is converted to CO2 + H20, which is removed by the lungs.
The increase in CO2 increases the RER, and it appears that "more"
carbohydrate is being expended when this is not in fact the case.

(Summaried from Wilmore and Costill's _Physiology of Sport and Exercise_,
2nd Edition, and McArdle, Katch, and Katch's _Essentials of Exercise
Physiology_).

: (depending on intensity level). However, your body is designed to SAVE
: AND SPARE fat. As Bill Phillips wrote in the 3rd supplement review
: (documented by some Journal of Medicine ..it's not like I memorize the
: references!) the amount of time humans as a race do not need to "hunt
: and gather" is a mere speck of time in our history. Our body is designed
: to store fat for times of famine, winters, etc.... That's why unless we
: consistently exercise aerobically for prolong periods of time, it burns
: the "active" energy in our system - and NOT our fat stores. 

Well, there's a very small grain of truth in this, in that fat is our 
primary means of storing excess caloric intake for later use.  It's a 
much more compact means of storing energy than making glycogen molecules.

However, that very same reason (that fat is easier to store than glycogen)
is precisely the reason that our body *preferentially burns fat all the
time*.  We have about 100,000 Calories of stored body fat, whereas we
have only about 1600 Calories of carbohydrate available (including glucose
in body fluids as well as muscle and liver glycogen).  If we tried to
preferentially run on glucose we'd be "out of the running" in only a few
hours.

Moreover, RER's at rest indicate that a substantial proportion (nearly 100%)
of our resting metabolic needs are met by fatty acid metabolism, and that
very little carbohydrate metabolism occurs at reast.

Finally, if you look at the metabolic pathways themselves there are 
several steps at which increasing levels of fatty acid oxidation can inhibit
glucose metabolism.  However, there are no corresponding mechanisms by which
glucose metabolism can inhibit fatty acid metabolism.  (See _Harper's
Biochemistry_ for a more detailed discussion).

Bill Phillips is a very charismatic guy, and he's making a lot of money
right now, but it's not because he's a world-class exercise physiologist.
The more people tell me about what he has to say (and the more I see/hear
him on TV) I am utterly amazed that someone with so poor a working knowledge
of basic physiology has catapulted himself to the position he has.

					larry...