Fasted workouts = fast track to success???

I’ve personally been doing fasted workouts for about two years now, and I’m a strong advocate for them. Granted, I typically workout in the early AM, so my fasting period is usually a good ten or so hours before I workout (if you start the clock from my previous night’s feeding). Aside from liking the feeling of NOT having food sloshing around in my stomach while I’m killing it during my workout, I’m a believer in the science/biochemistry behind why it may lead to overall improved fitness performance, as well as stoking the fat burning furnace.

The first-responder type fuels that are tapped during exercise are glucose and glycogen (the stored form of glucose). These are typically stored in the liver and the muscles. These are anaerobic fuel sources, and can be converted to energy w/o the help of oxygen. Think fight or flight – if you spring into action quickly before the body has a chance to increase respiration and oxygen consumption, something if fueling the action – that is your glycogen stores at work. If you haven’t eaten anything, the only glucose/glycogen in your body will be the stored stuff. The body burns through what it can, and then needs to switch to alternate sources of fuel. Fat is the next (and preferred) energy source, and is aerobic (requiring oxygen) in order to convert to energy.

fasted workout fuel tank

So, when I structure my workouts to get my heart pumping pretty quickly by doing (as a warmup)…

  • 3 minutes high knees jump rope with target heart rate (HR) of 140+ BPM, or…
  • 3 minutes half-mile run with target HR of 140+ BPM…

…I feel like I’m setting myself up to burn through stored glycogen quickly, and thus can turn on the fat fuel reserves quicker.

I will note that my first many HIIT sessions when I started with fasted workouts were pretty grueling. Everything thing I read supported this experience. It did get better/easier over time. Once fully transitioned, I’ve ran half-marathons in a fasted state, and even participated in a duathlon in a fasted state. In neither case did I feel like my performance was hindered by a lack of food. I just stayed properly hydrated, and plugged along.

It’s also worth noting that this type of meal-timing strategy works very well with my intermittent fasting lifestyle.

***VERY IMPORTANT CONSIDERATION – if you suffer from any type of metabolic disorder, diabetes, hypo/hyperglycemia, etc…, you should talk with your doctor before considering this type of nutrition strategy.***


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