The Death of Carb Loading

February 25, 2013

The Death of Carb Loading 

 Reference:The  Art and Science of Low Carbohydrate Performance by Volek and Phinney 

Remember carb loading your kids before a soccer tournament?  Ever done that yourself before a big event?  Ever tried to run a marathon and then “hit the wall” and “bonked” at mile 7?  These are all related events.  Volek and Phinney very elegantly explain to you just why this happens, and how it relates to the rest of us mere mortals who are just trying to lose weight. 

Here is the nugget of explanation.  Your body can store about 1500-2000 calories of glucose in your liver and muscles in the form of glycogen.  Your brain likes glucose and will use it preferentially.  But that’s it.  Just 2000.  When you carb load, several things happen.   You eat MORE than 1500 calories of carbs (usually quite refined, therefore invoking a rapid rise in blood glucose.).  This forces an insulin response whereby your insulin rockets up respond to those carbs and store them as in fat.  So you really don’t store any of those carbs. You really don't load anything.  They just get turned into fat.  More importantly, it programs your fat and muscle cells to adjust to a “carbohydrate economy” in which they burn carbs first before they burn fat. 

 If the carbs run out, your body becomes more efficient metabolically but doesn’t switch over to fat burning very easily.  It does that to protect your brain. Your brain can run on ketones.  Ketones are the broken down pieces of fats stored in your fat cells.  When glucose runs out, your brain starts to use ketones, and can do so quite happily.  So, first and foremost, your brain has to get energy before any other organ in your body.  The rest of your body politely and discretely waits until it is sure that the supply of ketones is secure.  In other words, it waits to make sure there aren’t more carbs coming down the pike. (Editor's note:  In 2022, we now know that conversion to ketones requires peroxisomes armed with sufficient enzymes to make that conversion.  Peroxisomes, proximal to mitochondria, have to get their enzymes from the nucleus.  That doesn't happen instantly.  It takes hours to days.)

 If you eat every 4 hours, you are always supplying carbs to your brain and your “carbohydrate economy.”  But you aren’t burning fat. If you are an athlete and run a marathon, you want access to more than the 2000 calories stored in your liver and muscles.  A marathon needs about 6000 calories.  Ask the question: do you want to run your marathon on the carb store you have, and supplement it by eating along the way with extra sugar?  Or do you want access to the 10% body fat you have (10% of 150 pounds is 15 pounds of fat equals 62,000 calories).

  You can run a lot further if you have access to your “fat economy”, and perform a lot higher.  That’s what Volek and Phinney have figured out in their research. The conundrum.  It takes about 10-14 days to switch from a “carb economy” to a “ketone and fat economy”. And once you do, you can ruin it quickly by having a burst of carbs.  But if you don’t have any carbs, you  open the door to a huge reserve of fats that get turned into ketones.  And then you lose weight, perform better on your marathon, don’t “bonk” at mile 7 or “hit the wall”. That 10-14 day delay is all about protecting your brain so that you are sure that it gets enough calories first.   Knowing that, you can design your own metabolic plan. 

 WWW.  What Will Work for Me?  This is all about weight control too.  If you want to lose weight, you have to eat below the threshold of instigating an insulin response.  Probably 50 grams a day of carbs is all you can get away with.  Fill that 50 grams with green vegetables.  And then always have access to your fat cells and watch the weight gradually drift away.  What’s an athlete to do?  Vegetable load.  Fat load.  But don’t carb load.  The carbohydrate meal should never happen before an athletic event.  Forget the spaghetti dinner.  It makes you worse.  Read the book!  It will change you.

This column was written by Dr. John Whitcomb, MD, Brookfield Longevity, Brookfield, WI.