You wouldn’t leave on a road trip without filling the gas tank in your car, would you? If a plane bound for your holiday destination neglected to fuel up before takeoff, the result would be even worse.

When you prepare for your workouts, filling the tank is just as important. Far too often, I hear of athletes “bonking” during workouts and I will be the first to admit that occasionally I have been guilty too. Even if you don’t get to the stage of feeling light-headed, you may still suffer diminished performance from starting out with less than adequate energy stores.

I recommend that you learn how to calculate the calories required for your planned workout ahead of time. There are several online calculators. Use one that takes your age, gender and weight into consideration. Several watches will also calculate caloric burn during a workout.

You also want to get to know your Basal Metabolic Rate or BMR, which is the number of calories you burn each day when not working out. Again, there are many online calculators for this. If you divide this by 24, you will have a ballpark figure for your hourly requirements, which is important in what I am discussing next.

For your workout, calculate the total caloric requirement and add it to your BMR. Subtract the hourly BMR calories based on the length of the workout. The reason for that is that during the workout you are exercising INSTEAD of resting. This becomes more important during sessions that last for several hours. Once you have added all this up, you know how many total calories you need that day.

Some calories will be consumed during the workout, but likely not as many as you are burning, so you would want to have those calories in your system prior to the workout. The practical considerations of this are that you may need to top up the day before an early workout. You may need to have an early light dinner before an evening workout.

The best type of extra calories for workouts are carbohydrates. Fat and Protein are too difficult to digest while exerting yourself. Your overall diet needs to be balanced and have a variety of fat, protein and carbohydrates, but for exercise fuel, carbohydrates are what you need.

Finally, my brief thoughts on fueling while on a weight loss plan. While it is understandable that you may be limiting caloric intake to shed a few pounds, you don’t want to over-limit that intake to the point of losing too much too quickly. Most experts recommend no more that 2 pounds of weight loss per week. Either way, high weight loss diets should be medically supervised. Within any restricted calorie diet, when you add calories is still very important. It is a good idea to completely top-up your fuel stores (no caloric deficit) before long workouts and also before high exertion workouts. If you need to limit intake, do so when light activity or rest are planned so you don’t “run out of gas.”

By starting each workout with a full tank of energy, you will get the most out of every training session.