From: mazur@inmet.camb.inmet.com (Beth Mazur)
Newsgroups: misc.fitness
Subject: Exercise and fat burning
Date: 29 Sep 92 16:05:56 GMT
Organization: Intermetrics Inc, Cambridge MA

Here's another academic reference to fuel the fire.  From p. 405 in
"Understanding Nutrition" (5th edition, Whitney, Hamilton, and Rolfes,
1990, West Publishing):

	...In contrast to fat in the diet, *body* fat stores are of 
	tremendous importance in exercise. Unlike glycogen stores, which
	are limited, body fat stores can fuel hours of exercise without
	running out; fat is a virtually unlimited source of energy. 
	Early in exercise, the blood fatty acid concentration falls as the
	muscles begin to draw on the available fatty acids. If exercise
	continues for more than a few minutes, the hormone epinephrine
	is released and signals the fat cells to break apart their stored
	triglycerides and liberate fatty acids into the blood. After about
	20 minutes of exercise, the blood fatty acid concentration rises
	and surpasses the normal resting concentration. It is during 
	this phase of sustained, submaximal exercise--beyond the first
	20 minutes--that the fat cells begin to shrink in size as they
	empty out their lipid stores.

	...Aerobic exercise draws heavily on fat for fuel, and the body's
	adaptations to exercise reflect that. For example, repeated 
	aerobic exercise stimulates the muscle cells to manufacture more
	mitochondria, the intracellular organellse that perform aerobic
	metabolism. Another adaptation: the heart and lungs improve in their
	capacity to deliver oxygen to muscles. Thus the body that exercises
	aerobically becomes well-suited to the task; its muscle fibers
	contain more aerobic metabolism equipment, and the body has a
	greater heat and lung capacity. These adaptations are not reserved
	for trained athletes only...Just 20 minutes of aerobic exercise,
	three times each week, stimulates even the untrained body to
	adapt by packing its cells with more fat-burning enzymes and by
	improving the ability of the heart and lungs to deliver oxygen.

	...After exercise has ceased, fat use may continue at an accelerated
	rate for about a day. At least some evidence suggests that metabolism
	is stimulated by about 25% for as long as three hours after intensive
	exercise and may still be running 10% faster two days later. It
	takes energy to link glucose molecules back into glycogen and to
	build new muscle tissue; fat supplies some of this energy. Exercise
	favors the continued liberation of stored fat, too. The body adapted
	to strenuous and prolonged aerobic exercise burns more fat all day
	long, not just during the exercise. In other owrds, intense exercise
	of more than an hour's duration probably raises a person's basal
	metabolism rate.

Gee, sounds like a Covert Bailey disciple to me :-).  BTW, I have just
started flipping through this book and would definitely recommend it to
people (I picked it up at the Northeastern University bookstore).

My college biology is 16 years old (and I didn't pay much attention at
8AM), but the science is definitely "accessible." 

Beth Mazur                   "...life is more than a vision.  The sweetest
mazur@inmet.inmet.com         part is acting after making a decision."
...!uunet!inmet!mazur                                  -- The Indigo Girls