Sunday, January 16, 2011
Pre-Workout: To Eat or Not to Eat...
The "Empty" Exercises:
This group claims that working out on an empty stomach is the best way to burn fat. They argue that if carbohydrate (glycogen) stores are empty then the body has no choice but to use fat for energy. Are they right??
Well... When you exercise without eating it does increase the amount of fat broken down in the muscles. So you may improve how the muscles burn fat, but unfortunately this will not affect overall body fat. It may be possible that more intense exercise could stimulate the burning of fat in other areas of the body - but it would take quite a bit of training to see significant results.
The First-Thing 'Fuelers':
This bunch says eating prior to exercise provides the energy and fuel necessary to perform optimally. This may be especially true when training first thing in the morning or following an extended period without food. The body has a limited supply of glycogen, (the storage form of carbohydrate), in the liver and muscles. Even though the body may have plenty of fat to use - it can't be burned in the absence of some glucose - more specifically, ATP (the first step of fat breakdown (oxidation) is an energy requiring reaction). When you go into a workout with an empty tank results in depleting the body's energy stores completely. This may result in a less intense workout (therefore you will burn fewer calories) or 'bonk' (trust me - you don't want to do it).
So, you might be asking, where did the energy to get me through my workout come from? It gets a little complicated here. It may be that your body entered a state of ketosis or a 'starvation' mode. What that means is fat starts being used for energy. That's good right? Well, yes and no... Ketosis is not an 'efficient' process. It doesn't happen immediately, may result in muscle loss; and since it's a survival mechanism, causes a drop in metabolic rate. Also, most people tend to 'overcompensate' on food intake later to plug the hole. So the net result ends up being a less than optimal workout, decreased metabolism, loss of muscle, and overeating. Additionally, exercising empty results in prolonged recovery time and potentially, a cruddy next workout.
A recent study, published in the International Journal of Sport Nutrition and Exercise Metabolism, compared energy/fat utilization markers (VO2 - oxygen consumption) and (RER - respiratory exchange rate) in fasted versus fed athletes. The VO2 and RER levels in the pre-workout eaters were greater than that of those in the fasted group at all measured intervals (during exercise, as well as 12 and 24 hours post-workout).
Ultimately the choice is yours; you've got some facts - granted there's also stuff out there claiming the opposite. My advice is this - if you're serious about performance and if recovery counts, definitely do not go in 'empty'. In the event you do decide to take the fasted approach don't expect to see the fat just 'melt' away, have your best workout, or recover quickly and optimally. Your meal doesn't have to be huge - some carbohydrate to fuel your muscles, a little protein to preserve them, and possibly a bit of fat to keep your stomach from growling if you're going long. And remember, you have to "Eat to Compete"!!