Once your Glycogen supply runs low, or runs out,your body turn to it's fatty acid supply as it's sole source of energy and athletic performance is negatively affected. Therefore, the more Glycogen your body can store, the better it is for both your health and performance.

All kinds of carbohydrates can help replenish the Glycogen stores.

Simple carbohydrates are readily used for energy, thereby sparing muscle Glycogen, when they are consumed during the training session; and they replenish Glycogen faster, within one to one and a half hours, when they are consumed right after training.

WATER CONSUMPTION is also important during the Glycogen-replenishment phase. For each 1 ounce of Glycogen that is stored in the muscle cells, about 3 ounces of water are also stored. Therefore,it is vital to keep your water consumption up.

For bodybuilders , it is the Glycogen-bound water that makes the visible muscles appear denser, fuller, and more striated. No matter what kind of athlete you are,make sure you drink at least 8 ounces of water with each meal.

(This is from "Dynamic Nutrition for Maximum Performance" by Daniel Gastelu and Fred Hatfield. An absolute killer of a book on Nutrition.
ISBN 0-89529-756-6 Avery Publishing Group 1997 )

Once your Glycogen supply runs low, or runs out,your body turn to it's fatty acid supply as it's sole source of energy and athletic performance is negatively affected. Therefore, the more Glycogen your body can store, the better it is for both your health and performance.

I agree if your an althlete but someone focused on body composition, burning fat has a fuel is very benefical.

From Dr.Hatfields book....


Energy Sources For BodyBuilders

"The muscles rely on three major systems to supply the energy they need---the immediate,glycolytic, and oxidative energy systems.For short term energy for explosive-strength output, the muscles depend on the immediate energy systems. the immediate energy systems are non-oxidative---that is, they do not use oxygen. Instead these systems generate energy through the use of Adenosine Triphosphate (ATP) and Creatine Phosphate (CP). CP is produced in the body and stored in the muscle fibers. It is broken down by enzymes to regenerate ATP, which is also stored in the muscle fibers.When the ATP is in turn broken down,the result is a spark of energy that triggers a muscle contraction.

For medium term energy for repeated near-maximum exertion, the muscles turn to the glycolytic energy systems. In these systems, which are also non-oxidative, glycogen is used to produce energy. Glycogen is the storage form of glucose. It is stored in the liver and muscles, and is readily converted back to glucose when it is needed for energy.

For long-term energy for endurance activities, the muscles use the oxidative energy systems. In these systems, oxygen is used to oxidize long-chain fatty acids, protein and glucose, which generates energy. For athletes, getting enough oxygen can mean a winning performance rathet than a second place showing.

The following table lists five different kinds of average WEIGHT-TRAINING sets and shows how much your body relies on each of the energy sources:-

Immediate Energy System

1-4 reps 90%
5-9 reps 80%
10-19 reps 60%
20-39 reps 50%
40-100 reps 40%

Glycolytic Energy System

1-4 reps 10%
5-9 reps 20%
10-19 reps 40%
20-39 reps 50%
40-100 reps 60%

Oxidative Energy System

1-4 reps 0%
5-9 reps 0%
10-19 reps 0%
20-39 reps 0%
40-100 reps 0%

Athletes (and bodybuilders are included here) whose muscles rely substantially on the immediate or glycolytic energy systems should keep their fat intake to a minimum because FAT is NOT an efficient energy source for intense training, which is almost exclusively ANAEROBIC in nature. Since the fat calories consumed by these athletes are not generally usd for energy , they are stored as body fat.

All athletes should consume a carefully measured amount of HIGH-QUALITY carbohydrates several times a day to ensure an adequate supply of energy."

And this is where your water intake comes into play, as described in the first post.

That's just one school of thought.

Near carb-free bulking using ketones can work in ideal circumstances as well.