Many athletes think that loading up on carbohydrates is the way to gain the edge in a competition. What is carb loading all about, and does it work?
Carb loading, or "muscle glycogen supercompensation", is about eating a large intake of carbohydrates right before a long term exercise trial, like running a marathon. The body carries its easy-access sugar stores of energy in the blood, the liver and muscles. The aim of carb loading is to overload the system with glucose, with the expectation that while some of the glucose goes into fat cells, some goes into the liver and muscles. Then, many hours later when the body is starving for energy, it finds that 'easy energy' right where it needs it.
Fat and protein are both considered more difficult for the body to metabolize - the typical body has been fed so much sugar that it's trained to use it best. For someone whose body has already been working hard for 4 hours and still needs to keep going, the body wants an energy source which is immediate.
Note that athletes that carb load also gain weight. The ratio tends to be that the body holds 3g of water for every 1g of carbs it stores. So for many athletes, carb loading turns into weight gain and a sluggish feeling. They avoid carb loading all together and feel they work out far better without the muscles full of sugar.
Studies have proven that womens bodies are not set up to carb load well. It appears that athletic men's bodies naturally use sugars well, while an atheletic woman's body naturally uses fat more easily. In one study, a group of female athletes were divided into three groups - one with no carb loading, one with carb loading plus supplements, and one with just carb supplements. There were no differences at all in performance.
One reason given for the apparent lack of effect in women but the effect in men is that men tend to have larger stomachs and simply can eat enough carbs to make a difference to their systems. A carb loading male must literally consume over 600g of carbs in a day in order to saturate his muscles with sugars and be effective. Even when attempting to eat complete carb diets, most women do not approach this level.
Other studies are showing that while carb loading may fill the muscles and liver with sugar, that FAT loading is even more effective. A study done in 1994 compared two groups of cyclists - one on low fat/high carb and the other on low carb/high fat. For high intensity workouts, both groups did equally well. For long, moderate intensity workouts (Tour de France), it was the high fat group that did better. There are other studies that show that increased healthy fat intake boosts endurance and oxygen consumption.
In the end, every human body is different. We all have different metabolism rates, different exercise rates, different foods we enjoy eating. But before you go with an exercise plan just because "everybody else does it", do some experimentation on what works best for YOU. You might easily find that eating a healthy low carb diet, and making sure you have enough healthy FAT in your system before beginning that event, is what propels you across the finish line.
Lisa Shea's Library of Low Carb Books