To eat or not to eat before heading to your cardio sweat session or favorite class? That is a common question, and not surprising due to conflicting recent research on this topic.

Several studies suggest exercising while your body is low on food may be a good way to trim excess fat. For example, European researchers found that cyclists who trained without eating burned significantly more fat than their counterparts who ate. The theory behind this is that since muscles usually get their energy from carbohydrates, if you haven't eaten before exercising your body doesn't have many carbohydrates in reserve, forcing it to burn fat instead. This is in fact a true statement, so skipping your pre-workout meal would seem like the right thing to do to accelerate weight loss.

Herein, lies the "twist" to these findings however. More fat was burned in a fasted state...DURING THE EXERCISE ITSELF. More current research shows that people who burn more fat during their workouts actually burn less fat the rest of the day. Fats and carbs have a "teeter-totter" type of relationship. As you burn more carbohydrates during your workout, the body will burn more fat post exercise. This "afterburn effect" where your metabolism is elevated for several hours or days following your workout is critical when debating the benefits of fasted cardio. In short, the afterburn effect is calorie burn AFTER exercise. The more intense the exercise, the greater the afterburn effect. For example, sprinting as fast as you can for 30 seconds for 5 rounds will have a much larger afterburn effect compared to jogging for 30 minutes. Furthermore, while you may burn more fat during your workout on an empty stomach, your overall workout output will be lower. Resulting in less ability to burn fat post-exercise. When considering a 24 hour period, cardio on an empty stomach is less effective.

These finding apply to BOTH moderate and high intensity exercise but in differing ways. In moderate exercise, research has shown that groups that ate before their session continued to burn significantly more calories up to 24 hours after the exercise bout. Therefore, fasting before moderate exercise does not enhance fat use as much as having a light meal pre-activity. In high-intense exercise (whether it be aerobic or anaerobic), most of your energy comes from glycogen (carbs). If you deplete your glycogen stores, you compromise your energy output/ability. As glycogen stores in the muscles and liver are depleted, and the blood glucose level begins to fall, fatigue, lack of coordination, light-headedness and lack of concentration can occur; Also known as "hitting the wall" or "bonking", because fat can't be metabolized fast enough to support the level of intensity.

So the take away message: Steady state fasted cardio might burn more fat during your workout, but your post-workout fat burn is compromised. Now I'm not saying to hit the breakfast buffet before heading out on your weekend jog. Something light and easily digestible is ideal, such as a piece of fruit, smoothie, a cup of oatmeal, protein shake, or a handful of trail mix. If you exercise later in your day and it has been 3 or more hours since your last meal, you should have a small snack pre-workout. So eat your Wheaties!!