The Official eNewsletter of TODAY! Fitness

vol. 2007 issue 3



Low Carb vs. High Carb Diets

When it comes to losing weight and keeping it off, both low carb and high carb diets actually have a principle in common that works. The principle that they both share is this:
  • Stay away from high glycemic index carbohydrates which can spike your blood sugar and insulin levels.  The Glycemic Index is a numerical index that ranks carbohydrates based on their rate of glycemic response (ie. their conversion to glucose within the human body).  The higher the glycemic index value, the more rapid the rise in blood sugar.
  • At the same time eat low glycemic index carbohydrates which will keep your blood sugar and insulin levels nice and even.

Having your blood sugar and insulin levels going up and down with big variations causes you to become hungry more frequently, which causes you to overeat. And as we all know, when you overeat you tend to gain weight. So this principle of staying away from high glycemic index carbohydrates explains why both diets seem to work when it comes to losing weight.

The more specific reason why is because while a low carbohydrate diet like the South Beach diet focuses on limiting carbohydrates (and only allowing carbohydrates that have low glycemic index values) a high carbohydrate diet like the McDougall diet focuses on whole, complex carbohydrates which tend to have low glycemic index values as well. This is why people who get on what seem to be completely different diets, the low carb diet and the high carb diet, can both lose weight.

What Kind Of Fuel Is Burning?

There is another interesting aspect to high and low glycemic index carbohydrates that have an effect on weight loss.  Your body secretes insulin to move blood sugar out of your blood stream and into your cells. But insulin also does something else. It turns out that insulin plays a role in determining just what kind of fuel mix our bodies burn during the day. Specifically, when high levels of insulin are secreted, the result is that your body is forced to burn carbohydrates rather than fat.

Let's say that over the course of 3 days, you eat a diet that is very high in high glycemic index carbohydrates. The result will be that a very high percentage of the fuel you burn will be carbohydrate. As a result, very little fat will be burned.

In contrast, let's say for another 3 days you eat the same amount of carbohydrates. Only this time all the carbohydrates you eat are in the form of low glycemic index carbohydrates. In this case, your body will burn more fat for fuel.

So not only will you not be as hungry if you eat carbohydrates that have low glycemic index values but your body will end up using more of the fat in your diet and more of the fat in your body as fuel.

Low Carb Weight Loss

One thing that often happens when a person switches to a diet where the carbohydrates they eat are dramatically reduced is there is a quick loss of body weight right away. The weight they lose, unfortunately, is often mostly water.

Your body has about 500 grams (just over one pound) of glycogen reserves stored in your liver and in your muscles. When carbohydrate is no longer provided in your diet in sufficient quantities, your body begins to use those glycogen reserves for muscle contraction and other needs. 

It is known that 1 gram of carbohydrate in your body, in the form of your glycogen reserves, binds with 4 grams of water.  So when you use up your 500 grams of glycogen reserves over the course of the first few days you are on the new low carbohydrate diet, you end up losing 2,000 grams (500 times 4) of weight in the form of water.  Now add in the 500 grams of glycogen that your body used up as well during that time and you have a total of 2,500 grams or 2.5 kilograms (5.5 pounds) of weight that you have lost.

Although that may sound good to some, none of that weight you lost was body fat!  It was all water and glycogen. This biochemical process is what often accounts for the quick weight loss that people experience when they first go on a low carbohydrate diet.

Low Glycogen Reserves

Virtually everyone knows that regular exercise should be included with a weight loss program. But have you ever tried to exercise when your glycogen stores are very low? Believe me, it's not fun at all. It's very hard because you have no energy. So a low carbohydrate diet may create a tired feeling in your body and prevent you from wanting to exercise.

When your body runs low on glycogen reserves, it will actually start to break down muscle tissue in order to create glycogen to feed your brain. Remember, your brain is fueled almost exclusively by carbohydrates.

The point is that with this kind of low carbohydrate diet you end up not only losing weight in the form of water and glycogen but you end up losing muscle mass also.  And it is the muscle mass that you want to build or at least maintain in order to have a way to burn stored body fat.  Metabolism increases as muscle mass increases.


Elite Bodyweight Exercise of the Month!

Full Crunch

The full crunch is one of the more popular abdominal exercises for those that want to bump up the intensity on a normal crunch.  With both the upper and lower abdominals engaged, this exercise gives you a great bang for your buck.


Target:  Upper and lower Abdominals (rectus abdominus)

Count:  2 count

Description:  Starting position lying flat on your back with your legs straight in leg lift position.  With your hands lightly behind your head, crunch your shoulders up and your knees towards your chest at the same time.  Return to starting position and repeat.

Carbs Converted To Fat?

Contrary to popular belief, it turns out that studies of the science of biochemistry in humans say that excess carbohydrates in the body, it turns out, are not converted to fat!

Without getting into a lot of details, the main reason that carbohydrates are not readily converted into fat in the human body is because it is very inefficient from a metabolic standpoint and requires a lot of energy to do it. And the human body is a very, very efficient machine by design.

What actually happens is any excess carbohydrate that isn't used immediately by the body for its needs is stored as glycogen in the muscles and in the liver and the rest is simply burned and released as heat through the skin and lungs.  The body just doesn't want to convert carbohydrates into fat.

Now, if a person were to eat a TON of carbohydrates day after day after day then, yes, the body will begin to convert it to fat. But it would require a person to eat more than 5,000 calories a day, all in the form of carbohydrate calories.  With carbohydrates being quite low in calories, that's an enormous amount of food that a person would have to eat. In fact, 5,000 carbohydrate calories a day equals about 33 potatoes that you would have to eat every day before your body would begin to start converting the excess carbohydrate as fat.

Why Do People Get Fat?

If science has shown that your body doesn't convert excess carbohydrate into fat, what exactly is going on then with people who are supposedly eating large amounts of carbohydrates and are getting fat? What is actually happening is this:
  • they are eating high glycemic index carbohydrates, usually in the form of highly processed foods that also have fat in them.
  • they are staying hungry all the time, are overeating and the large amounts of fats that are in their diets are making them fat.

In summary, here's what to remember when it comes to losing weight and keeping it off.

  • One of the causes of getting fat is overeating. If you want to make it easier to stop overeating, add a lot of low glycemic index carbohydrates to your diet.
  • If you want to have your body burn a larger amount of fat as fuel, cut out the high glycemic index carbohydrates in your diet.
  • The quick weight loss that people often experience when they go on a low carbohydrate diet is water and glycogen, not body fat.
  • There is way more fat in your diet than you realize, especially if you are eating highly processed and packaged foods.  Instead of stuffing yourself with foods that have a lot of fat in them, stuff yourself with low glycemic index carbohydrates.

It's Go Time!

I never liked the term "diet".  Diets are typically thought of as short term plans that you have to endure until you reach a goal or give up trying.  The negative feelings associated with diets don't do much for your motivation either.  If you make permanent changes in your eating habits that you can sustain over time (portion control, less deep fried foods, cut down on "junk food"), you will get used to these changes as they become habit and realize more permanent benefits than a "diet".

If you've been reading my eNewsletters you probably have already heard me talk about "Smart Eating".  Understanding the effects of the glycemic index on your body is a good way to become more educated in nutrition concepts so that you can make better food choices.

I am not a registered dietician, but I can tell you from personal experience that there are a lot of practices that you can change, without starving yourself, that will add up to significant progress.  If you have trouble adhering to typical diets, start with smaller changes to your every day eating and progress a little at a time.  The bottom line is that you want to find a beneficial long term program that you can stick with... forever!

For prior issues of this newsletter go to  

Good Luck!

Pete Mazzeo, CPT

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