If you are doing a moderate workout of 30-50 minutes then fueling your body before workout is not required. The energy required for the workout session is enough from our daily consumption of meals. Fueling before workouts also depends whats your objective is , whether it is losing weight, building muscles, toning up etc. Only if you are working out for a very long period like marathons then extra energy is required. Regular workouts do not require additional energy.
To increase efficiency in the body it is important to keep the fluid levels balanced. Dehydration and less fluid leads to cramping and decreased release of energy for the body slowing down the metabolism. Water is sufficient to keep you hydrated during your regular gym workouts. Energy drinks and bars are required for marathon trainers or bicyclers where they train for hours. Eating high carbohydrate food or drinks before or during the workout only adds to the calories.
Timing the meal is important as if you overload yourself then you would feel sluggish, vomiting, feel heavy to actively move around etc. If you haven't eaten for much time before a strenuous workout then you will feel fatigued and have a heavy head and not feel comfortable and concentrated. Plan your meals atleast two hours before the workout for effective results.
Diet: Choose carbohydrates before a meal as they are more important for providing energy for the workout and maintaining the glycogen levels. Choose complex carbohydrates which quickly breakdown for energy and eat less of fibre before a workout.
Fuel your self rightly and don't experiment on yourself. Eat protein rich food post workout for muscle recovery and growth of muscles. Push yourself and reach higher fitness levels. Keep the water levels recovering and become all the more resistant.