I’ve talked about fasted state morning cardio a number of times on the forum; here is a section of a recent article of mine:
This is probably the most confusing and misunderstood topic when speaking of matters of active nutrition?when is the best time to consume a meal in relation to cardiovascular activity? In order to answer this question, we must consider the most favorable way to:
Maximize performance- Now, you may be thinking “I don’t care about performance; I’m not competing in a race; I just want to lose fat!” This is a very common attitude; however, it’s not a very smart one. Exercise intensity is directly related to the amount of calories and fat you burn as a result of a given workout. If your performance is suffering from a lack of proper nutrition, you won’t be losing fat at an optimal rate; period.
Optimize fat loss- Obviously, we don’t want to hinder the amount of fat lost either during or after the exercise session; therefore, we have to consider whether the method we choose to supplement in has any adverse effects on fat loss.
Minimize muscle loss- Many times trainees will compromise large amounts of hard-earned muscle mass while dieting. A major contributor to this sad occurrence is the failure to appropriately time meals to combat the catabolic influences of exercise.
Now, it was originally thought that while consuming a meal before exercise may have a positive effect on performance, it would certainly have an adverse effect on the amount of fat lost as a result of that session. Consequently, consuming a meal prior to exercise was frowned upon and performing cardio in a fasted state became the staple recommendation to optimize fat loss. However, all theory aside, research has shown this not to be the case. Let’s take a look:
Study #1 - Cardiovascular and metabolic responses during 30 minutes of treadmill exercise shortly after consuming a small, high-carbohydrate meal.
Diboll DC, Boone WT, Lindsey LR. Int J Sports Med 1999 Aug;20(6):384-9
Procedure: Subjects either fasted or consumed a small, high-carbohydrate meal prior to 30 minutes of treadmill running.
Results: The researchers found no difference between groups in energy substrate utilization during exercise (i.e. the amount of fat vs carbohydrates used during exercise).
Study #2 - Respiratory gas-exchange ratios during graded exercise in fed and fasted trained and untrained men.
Bergman BC, Brooks GA. J Appl Physiol 1999 Feb;86(2):479-87.
Procedure: Subjects exercised after either an overnight fast or three hours after breakfast.
Results: There were no differences in substrate utilization during exercise when working at moderate to high intensities.
Study #3 - The effect of a preexercise meal on time to fatigue during prolonged cycling exercise.
Schabort EJ, Bosch AN, Weltan SM, Noakes TD. Med Sci Sports Exerc 1999 Mar;31(3):464-71
Procedure: Subjects exercised in a fasted state or 3 hours after consuming 100g of carbohydrates.
Results: It took longer for those who consumed the carbohydrates to fatigue, and again, no difference in substrate utilization during exercise.
As you can see, consuming a small meal prior to exercise will likely improve your performance and will not adversely effect the amount of fat burned during your session. Also, it should be noted that performing cardio in a fasted state is very catabolic not only to fat stores, but also to muscle protein. Continual use of such a method will likely cause lean tissue loss, especially when constantly in a state of negative calorie balance (as is the case when dieting).
Another common recommendation has been to wait an hour after exercise before eating in order to take advantage of the substantial increase in metabolism that occurs as a result of high intensity exercise. This hypothesis was recently studied by Dr. Lee and the Department of Exercise Science at the University of Se Jong in Seul, Korea. He and his research team founded that those subjects who consumed a protein and carbohydrate beverage actually increased the amount of calories burned during the hour post exercise while still having no effect on substrate utilization. Also, proper post workout nutrition will help prevent lean muscle mass from being catabolized and used as energy during this time frame.
Hopefully by now it should be easy to see that consuming meals both prior to and immediately following intense exercise is the best way to 1) maximize performance, 2) optimize fat loss, and 3) minimize muscle loss.