For bodybuilding--horrible idea. Complex carbs, such as those derived from grains, tubers, or legumes, are essential to maximizing muscle growth. They also provide benefits in about a dozen other areas that are beneficial to bodybuilders.
If you don't have to go "grain-free", don't. However, I DO advise eliminating refined carbs in favor of unrefined carbs. Refined carbs, such as high molecular weight carbs, can be beneficial when consumed at certain times, such as intra-workout, but for the most part, unless there is a good reason to consume them, they should not be part of your diet.
The large majority of a bodybuilder's complex carb intake should come from unrefined carbohydrates, such as whole-grains (wild rice, barley, oats, etc), tubers (white potatoes, sweet potatoes, and other root vegetables) and legumes (beans, peas, etc).
Unfortunately, most bodybuilders consume far more refined carbs than unrefined ones, opting for foods such as white rice. White rice is basically like white bread--completely stripped of not only its nutrients, but also of its natural fiber content, which the overwhelming majority of bodybuilders are deficient in.
Tubers and legumes are usually consumed in their unrefined form, as they lack the 3-layer make-up characteristic of grains. However, grains, which just so happen to be the most popular source of complex carbs for bodybuilders, are most often consumed in refined form.
Grains are composed of 3 components--the bran, germ, and endosperm. The bran is the outer shell, which contains most of the fiber, as well as some vitamins, mineral, and phytonutrients. The germ is the part of the grain that grow into a plant when germinated. It contains the vast majority of the grain's nutrients, including vitamins, minerals, phytonutrients, fatty acids, and various aminos acids. It is BY FAR the most beneficial part of the grain. The endosperm is the part of the grain which the germ uses as an energy source, to help it grow into a plant post-germination. It is sparse in nutrients, but loaded with calories in the form of complex carbs. Using rice as an example, the endosperm would be the "white" part of the rice. The endosperm comprises about 70-90% of the grains weight, depending on the type of grain.
Refined grains, such as white rice , contain ONLY the endosperm. It is has been completely raped of the bran and germ, leaving nothing but a source of calories. By consuming only the endosperm, the individual is not only going to miss out on a ton of potential benefits, but it also has negative effects on whole-body health.
The benefits of whole grains are numerous. There are a lot of excuses provided by some bodybuilders, as to why they choose to consume refined grains instead of refined versions. The most common is that "they are easier to digest". Don't confuse this with digestive health, as whole-grains are far superior in terms of digestive health than refined grains. Easier to digest should be properly interpreted as "quicker to digest", nothing more, and in most cases, this is actually a bad thing.
The bottom line is that a bodybuilder should never eliminate unrefined carbs from his diet, unless he needs to. The optimal amount a bodybuilder should include in his diet can vary enormously, but eliminating them completely is a bad idea.
Regarding fruit and vegetable intake, this is also an area that the typical bodybuilder severely neglects. Most bodybuilders should be consuming far, far more of these foods than they do. Failing to do so will have significant negative effects on health and overall functioning. There is a lot to say on both of these subjects, but this post is already getting too long and off-topic, so I am going to stop here.