Many of my athletes ask: Should I workout in a fasted state or should I fuel up before I workout. The answer to this question is complex. First it depends on whether the workout will require glycogen to help you sustain your performance while working out. Second, the answer is really dependent upon the person. With the grey answer behind us, there is research that supports this conclusion.
An empty stomach triggers many hormonal changes throughout the body. First, fasting impacts the production of insulin. In a previous Knowledge post, I talked about how to use a spike in insulin to help you with your workout goals. Again, the basics is that insulin when used at the appropriate time, will help direct the sugars in the bloodstream to build muscles, and use fat cells as energy. However, if we eat too much or too often it makes our body more resistant to insulin’s effects. This resistance makes it hard to burn fat efficiently. So fasting is one way to to avoid this insulin resistance. However, I am not a big fan of fasting for it’s own sake. Moderation of diet, with theoccasional “earn your cheat meal,” is the basis of my nutritional philosophy. Fasting, however does make it easier to lose fat, and improves blood flow to the muscles.
The magical growth hormone (“GH”) is also positively impacted by fasting. GH helps the body make new muscle tissue, burn fat, and improve bone quality, physical functioning, and longevity. I always say that regular weight training and proper sleep helps increase the production of GH. Fasting also positively impacts the body’s production of GH. One study showed that fasting can impact GH production by 2,000% for men and 1,300% for women.
So, when you mix exercise with fasting, it not only produces both more testosterone due to the weight lifting, and more GH from the working out in a fasted state. This creates an optimal environment for building muscle efficiently.
Intense exercise that uses a lot of muscles, such as deadlifts and front squats – two of my favorite exercises – causes a big surge in the production of testosterone. Studies have shown that working out in a fasted state is a terrific way to build lean mass and boost insulin sensitivity. In addition, working out in a fasted state makes the body’s ability to absorb the post-workout meal more efficient.
In sum, fasted state training helps to ensure that carbs, proteins and fats go to the right places, and minimizes the storage of them as fat. Studies also show that athletes who train while fasted become more efficient at burning fat at higher levels of intensity.
Even if you’re not interested in gaining muscle, endurance athletes can benefit from fasted workouts. Endurance athletes an improve muscle glycogen storage efficiency. So doing your aerobic exercises while in a fasted state will help your body use that fat which is stored as energy.
However, if you have a big workout that will require a lot of energy over a longer period of time, I recommend fueling up before the workout, so that you don’t negatively impact your performance. You will run out of energy during an intense and long workout in a fasted state. You will need more glycogen that your body has stored, in order to sustain optimal performance. Therefore, fuel up for these types of workouts.
In conclusion, I recommend an occasional fasted workout if that workout will be short to intermediate in terms of duration and intensity. This will help you burn fat and build lean muscle mass. I don’t recommend consistently working out in a fasted state, or fasting on a regular basis. I recommend eating in moderation, and using insulin spikes to help with body repair as I described in the Knowledge post a couple of week ago.
