Our bodies were designed to extract energy from a balance of macronutrients and carbs are very important in the mix. For those occasional snack attacks, there are many easy snacks that really pack in a lot of nutrition. There are many delicious choices of breakfast bars and meal replacement shakes currently available to accommodate the busy modern lifestyle. If it works for you and helps you get the nutrition you need, then there is no reason at all why you can't substitute them for a meal. When combined with fresh fruit or yogurt, a fairly nutritious meal can be made.
Convenience is the key.
Some recommendations would be microwave or air popped popcorn, graham crackers, grapes, chopped up bell pepper or carrot sticks, pineapple chunks. Even those breakfast bars we talked about above come in many low-fat varieties. Juice is also a good quick energy boost. This is eating several mini-meals throughout the day, and this often accommodates the active life style. As long as food choices add up to the recommended levels of macronutrients, eating five or six mini meals can be as nutritious as the three meal per day eating style.