Sugar highs

So I've talked about the myths of protein and energy, and how your body creates energy, but I've had a very difficult time understanding the relationship between food and energy.  And I just realised that's because I've been asking the wrong question; the right question is, what's the relationship between food and your brain?

I've talked about the sugar cycle -- how your body breaks down food into simple sugars, putting them into your bloodstream with oxygen for the mitochondria to convert to energy (the "krebs cycle") -- but that doesn't explain why you have an "energy boost" when you eat pure sugar.  Anyone can tell you it's because the sugar is easily absorbed into your bloodstream, creating a "sugar high."  Of course, they'd be dead wrong.

They would be correct in that your blood-sugar level will spike, which in turns causes the pancreas to release insulin, which tells cells to absorb the sugar and convert it into glycogen or triglycerides for storage.  (Type I diabetics don't produce the insulin, and Type II diabetics don't respond to insulin; either way it is a problem because sugar molecules are larger than blood capillaries, and so if they aren't removed quickly, the capillaries will burst.)

However, the blood-sugar spike has nothing whatsoever to do with the "energy boost"!!  Your brain, through evolution, has been hard-wired to reward you for eating certain types of foods, notably the ones that have historically been difficult to find in nature: fat, salt, sugar.  So while your body is dealing with a physiological response to sugar, your brain is producing endorphins as a reward for eating it!  Those endorphins give you that "high" but are all too quickly absorbed, which then causes a "crash."  But this only has to do with your mood, and nothing to do with your body's energy level!

If you eat low-GI foods (ie. complex carbohydrates that take longer to break down, and thus don't increase your "glycemic index" level dramatically), you will be doing your body a favor because it won't be having to deal with the sugar spike, and it won't be storing all those sugars.  However, your brain isn't going to reward you for eating those foods -- thus you don't experience the mental highs (and lows), either.

Caffeine (and other stimulants) are another kettle of fish.  Although you may feel your body's physiological response -- increased heart rate, nervous jitters -- you are actually messing with your brain, because caffeine binds to adenosine receptors.  Adenosine is produced when brain cells fire, and it inhibits brain cells from firing--that is, it's part of your body's natural feedback system to keep your brain from become overexcited, and is also part of your sleep cycle. Caffeine blocks the adenosine, allowing your brain cells to continue firing.  However, while caffeine may make you feel sharper and smarter, measurable performance is not greatly improved!  As someone put it, it's not so much putting your foot on the gas as taking your foot off the brake.

For reasons that aren't yet clear to me, the over-stimulated nerve cells then release the hormone epinephrine (adrenaline), which is part of the "stress response" (or fight-or-flight response) which increases heart rate, blood pressure, and blood flow to muscles, decreases blood flow to the skin and organs, and causes the liver to release glucose, all in preparation for the body to use energy in a short outburst. That's fine if you're about to fight somebody (or do a heavy workout), but not so much if you're going to go sit at your desk and make a phone call.  I've been reading lately about Dr. Bruce Ames' "triage" theory of aging -- that is, your body's response to short-term survival is at the expense of long-term health. That makes sense at an evolutionary level, but when we deliberately induce a short-term survival mechanism, 3 or 4 times per day, you really do have to wonder what the long-term health indications are.

So to summarise, unless you are actually starving and have 0% body fat, there is no link between food and your body's energy level.  Your body is wonderfully efficient at maintaining a consistent energy consumption (your metabolic rate), just as it maintains a constant body temperature, only making short-term adjustments to deal with specific threats.  On the other hand, your mind is a mess.  It's a chemical soup of producers and receptors for a host of chemicals, all of which impact the way you feel from one moment to the next. For millennia, it's had to deal with a shortage of food; it hasn't adapted to deal with a surplus.  That's why it encourages you to eat a Big Mac even though you already have plenty of fat stores!

The good news is, it can be trained.  Dr Kessler, who tried to bring cigarettes under the auspices of the FDA, has written a book called, "The End of Overeating."  In it he compares health attitudes towards cigarettes, going from "sexy and glamorous" to now "foul and disgusting," even though nicotine has a similar effect on the brain to caffeine.  He suggests that in the right cultural climate, we can do the same to fast food, thinking of it less as a "reward" and more as something you wouldn't want to do to your body.

Of course, just like cigarettes, this will take time and discipline.  And unlike cigarettes, the long-term results aren't so obvious.  However, it will be a glorious day when Big Macs actually carry cigarette-style warning labels: "Eating this product will make you fat, increase your cholesterol level, cause mood swings, sexual dysfunction,  depression, lethargy, headaches, and heart palpitations."