Low-carbohydrate diets may be all the rage but many dieticians warn that skimping on this nutrient could rob your body of energy, especially during exercise.

"Carbohydrates are one of the basic nutrients that supply energy to the body," said Dr. Rebecca Reeves, a registered dietician with Baylor College of Medicine's Behavioral Medicine Research Center in Houston. "This is the energy source the body looks for, and it is what it burns when a person starts exercising."

The body transforms carbohydrates into glucose and transports it to the cells for energy. Carbohydrates also replenish spent muscle-glycogen stores. If your body is not well stocked, your workout could suffer.

To get the most out of this energy source, choose complex carbohydrates like dried beans and peas, whole grain foods, and cereals like oatmeal.

The duration and intensity of a workout will dictate carbohydrate needs. Most recreational athletes need 50-55 percent of calories from carbohydrates. Elite athletes, however, will require more.

The bottom line, says Reeves, is to remember that cutting carbohydrates means cutting an energy source.