Summary for the Busy Executive: Your Metabolism

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You've probably seen these headings: "Summary for the Busy Executive."  Most times it is tongue-in-cheek --as it is here-- but one does get the impression that Executives do not like to read much.  On the face of it, it seems to be because their time is so precious, but mostly it is because they read so little that they've lost the ability to read fast.  I'm a little like that, and I'm not even an executive.  I just sit here, writing blogs, with as many words in them as I can manage, except this one.

For your muscles to work, they have to get power from somewhere, just like an appliance.  There are two sorts of work (usually, and a third sort of work that you can safely ignore for the moment, which I will describe later):

Brief, low-intensity work.  Just getting up from your chair and walking across the room to turn the TV on, or the radio off, or eating, or reading the newspaper; this is all low-intensity work, and usually proceeds in spurts.  Reading, of course, can be a protracted (long-duration) activity, but it still falls into this class.  All this kind of activity is fueled by plain old sugar.

Moderate-intensity work for long periods.  This includes anything that is moderately strenuous, such as walking, slow running, swimming, rowing, riding (a pushbike or even a horse, I suppose), and easy hiking, as long as you do it for some time.  This sort of activity starts off burning sugar --we always have a little sugar in the blood-- but, after about 20 minutes, the body starts to dig up fat from all the places in which it has been stashed, e.g. big arm and leg muscles, and around your waist, and starts burning that, very slowly.  A gram of fat --as far as I know, and don't quote me on this-- has as much energy as ten grams of sugar, so once this process has begun, you sort of cruise along.  This is often called the second wind, which cuts in after you've been walking or running or yelling or singing or swimming for more than about 20 minutes.

It seems that, with training, people can get into the fat-burning zone a little faster.  This just might be an old wives' tale.

At any rate, burning fat needs a little more oxygen than burning sugar.  You have to breathe a little harder, but not enormous gulps of air, or anything.  When you're walking your dog for any distance, you notice them panting; part of that is that they perspire through their breath, so they have to cool down that way.  But some of it is, yes, getting into the fat-burning zone, and you might get just a bit breathless, too.  This is why it's called aerobic exercise; fat-burning uses up more oxygen than sugar-burning.

If you are very short of breath, that's different.  Your muscles are craving the oxygen, but your heart can't do the job.  It's trying to pump like crazy, but your arteries are all clogged up, and the body blames the lungs, so the lungs work harder, but all for nothing.  Ironically, the treatment of this situation will probably involve a combination of drugs, exercise, and, unfortunately, possibly surgery.  I would have it done, because it is a serious quality of life issue.

Once again, let me emphasize that the amount of fat you burn is proportional to the amount of time you exercise after getting into the fat burning zone.  So if you get into your fat-burning state after exactly 20 minutes,
You burn zero grams of fat if you stop right then;
You burn twice as many grams of fat if you exercise for 10 minutes more than if you exercise for 5 minutes more.

This morning, I went for an easy walk out to Dunkin' Donuts.  Predictably, I started breathing a little harder just around the 25-minute mark.  It was nearly half an hour into the walk when I hit the old doughnut-and-coffee hole, at which point I bought a cup of coffee, which was singularly disappointing.  It was weak, and I had asked for milk, and they must have put in skim milk, or something like that.  So it was healthy, but tasted horrible.  The things I do for my health!

Then I turned around, and walked home.  This time around, I suspect that I hit the aerobic state more quickly, and I got the benefit of another good 20 minutes of exercise.  Notice that those first twenty or so sugar-burning minutes do not burn fat at all.

Finally,

Brief, high-intensity activity.  I mean things like a sudden sprint, or lifting a very heavy object a short distance, or playing a point in tennis.  For these short bursts, the body actually burns protein.  The body is left with a little lactic acid, which, if it accumulates, gives you a painful cramp.  Obviously, unless you want to actually burn off your muscles rather than your fat, you don't want to do this sort of thing for therapeutic reasons.  If you just have to do it as part of your job, or something else that is important, like spring cleaning, well, okay.  Competitive tennis is hard on the body.  Recreational tennis, on the other hand, could be an aerobic activity, depending on how you play.

In all that preceded, I avoided actually making suggestions; but the principles are easy enough for someone who is in moderately good health to know what is beneficial and what is not.  If your health is poor, you need expert advice to avoid activity that your body is not ready for.  Generally speaking, slow walking for 25 minutes would be the least dangerous exercise, only coming next to slow swimming for 25 minutes.  The water supports your weight, taking some of the load off your heart, but also gives a little resistance, which is good.  This is especially suitable for people with very small feet, which would have trouble supporting your weight for long distances.  Small feet look lovely, but are rather a curse when you want to walk.
 

If you want to walk, get the best supporting sneakers you can afford.  'Nuff said.

If you're diabetic, don't go more than a 3-minute walk from a source of sugar, or take a source with you, e.g. an emergency can of orange soda in your backpack.  (And drink sparingly as needed; most orange soda contains like 30 grams of sugar.)