Breakfast is the most important meal of the day. You need to fuel your workout. You’ll go catabolic if you train in a fasted state. You’ve heard all of these tales and perhaps they do have some relevancy. But you get up at 5am to hit the gym before work and the last thing you want to do is shovel in some eggs and toast. This article will lay out some of the costs, benefits, and dispel the myths of fasted training.
Fasted training simply means working out on an empty stomach. The intermittent fasting (IF) craze has led to increased popularity in fasted training, or at the very least peace of mind with it. It’s no longer taboo to train fasted with more and more people practicing different levels of IF. I’ve done fasted and fed training for quite some time and feel I can illuminate on the good and the bad from both a scientific and anecdotal perspective.
Pro: Improved Insulin Sensitivity
Insulin is a hormone released by the pancreas after ingesting a meal. It helps to shuttle nutrients into cells so that they don’t remain in the bloodstream for too long (as this can potentially cause damage). In a perfect world you wouldn’t need much insulin to accomplish this task. When you need more and more insulin to do so, this is called insulin resistance. Basically your cells are no longer sensitive to the insulin being released, so the pancreas responds by pumping out more and more. When this reaches an extreme level, an individual can develop type II diabetes.
As a healthy individual, this probably isn’t a concern for you. But is there a way to use this to our advantage? We mentioned that insulin’s job is to remove glucose and nutrients from the bloodstream into various cells. But one thing to consider is that insulin does so indiscriminately. In other words, it doesn’t care what cells it drives these nutrients into just as long as it gets them out of the blood ASAP. Resistance training changes the game however.
Working out makes your muscles far more sensitive to the nutrients you eat. When you resistance train, transporters called GLUT4 move to the surface of the muscle cell you just stimulated. If you just finished a leg workout for example, your quads and hamstrings will be more receptive to nutrients compared to other cells. At this point insulin is no longer indiscriminate, it will defer more nutrients to that muscle because of exercise.
This is why I’ve always been an advocate for nutrient timing. You should take advantage of this phenomenon and structure your diet accordingly (more on that later).
Con: It is Not Optimal for Muscle Growth
But you just said it improves insulin sensitivity! It does, but there’s always a tradeoff. Your training sessions are sacred. They are the greatest opportunity each day to make major changes to your physique. If you want to optimize for muscle growth you want nutrient-rich blood flowing to the muscles WHILE you train. This means having something before or during your training session. Training hard in a fasted state, while it does improve insulin sensitivity, could leave you in a catabolic hole that is hard to dig out of. Remember, working out even in a fed state does this as well to a slightly lesser degree.
This doesn’t necessarily mean you have to scarf down a meal before you train if you don’t want to. You can circumvent this by consuming an essential amino acid intra workout supplement mixed with a carbohydrate powder. You drink water while you train anyway so it’s not as if this would be a dramatic change to your routine. This ensures that you are maximizing all resources to build muscle and get the most out of each workout.
Want to get the best of both worlds? Here’s what I would do:
If you have just gone through a long period of caloric surplus (bulking) and you’re concerned that your insulin sensitivity is not as good as it can be, train fasted for about a week. This should be enough to get you back to where you want to be. Then you can return to proper nutrient timing around your workout; whether it’s a pre workout meal, intra workout supplementation, or both.
As an aside, nutrient timing is particularly critical if you are in a cutting phase. If you are eating at a deficit to lose body fat, you want to consume a disproportionate amount of your calories around the time of the workout (pre/intra/post).
Pro: Improved Workout Performance
This varies from person to person, but anecdotally I can tell you most people don’t like to train on a full stomach. I certainly don’t. I feel sluggish, slow, and bloated. As mentioned previously, your workouts are key. You need to be able to give 100% each time if you want to progress. I said before that to optimize muscle growth you have time nutrients around your workout. But you never want to sacrifice 90% to get an extra 5. If doing things by the letter of the law means your workouts suck, then don’t do it!
Con: Less Room For Error
If you train in a completely fasted state, without even intra workout supplementation, post workout nutrition is absolutely vital. The idea of the anabolic window is somewhat misunderstood, but in this situation you do want a high quality protein and fast digesting carbohydrate as soon as possible after the workout. In other situations, this is less important. For example, if you consumed a pre-workout meal or intra-workout drink, your body is already getting the nutrients it needs to repair and rebuild. The urgency of a post workout meal isn’t as critical.
As alluded to before, your workouts will be particularly catabolic when training fasted. If your nutrition isn’t on point, you will notice. There have been numerous times where I trained early in the morning and had clients immediately after without time to eat a proper meal. By early afternoon I’m toast. My rice will be done in the rice cooker and all I have to do is go and microwave the chicken, yet I can’t get up off the bed.
In this situation (and honestly even if you don’t train fasted), your post workout meal should be the largest meal of the day. If should be high on the protein and carbs and low on the fats and fiber. Fats and fiber have their place, but they slow digestion. Post workout you want something fast digesting that will get right into the muscle.
Myth: You’ll Go Hypoglycemic
The theory is that a workout coupled with low blood sugar from not eating will cause you to get dizzy and pass out. Well, your body is much smarter than to let that happen. The body stores carbohydrates or sugar in the form of glycogen in both muscle and liver. In times of need, a hormone called glucagon is released which signals the body to release those carbs to keep blood sugar stable. In addition, this gives you the energy needed to exercise.
If you train without eating and experience dizziness then you should obviously stop, but it’s also an indication that there may be some metabolic dysregulation and you may have to work your way up to fasted training (or just not do it at all).
Conclusion
Hopefully this eases any apprehension from people who train early in the morning on an empty stomach. If you structure your diet appropriately for the rest of the day you can make it work. I want to summarize with a breakdown of each scenario to help you get the most out of your training.
For Optimal Muscle Growth – Not Fasted
Pre Training: Balanced small meal with protein, carbs, and fats. (i.e. a protein bar or a few whole eggs with toast)
Intra Workout: Essential Amino Acid Powder with 25-50g Carbohydrate Powder mixed in 32oz. water
Post Workout: Standard bodybuilding meal lacking in fats like chicken and rice
Optimizing as Best as Possible – Fasted
Pre Training: None
Intra Training: Essential Amino Acid Powder with 25-50g Carbohydrate Powder mixed in 32oz. Water OR None
Post Workout: Large meal with high quality protein source like chicken and mix of glucose and fructose containing carb source (i.e. rice and a piece of fruit like apple/banana). A disproportionate amount of your daily carb intake should be in this meal.