4 Ways That Fasting For 16 Hours Has Improved My Fitness

Written by Nora Tobin
Nora Tobin is a NASM-certified personal trainer and the Health and Wellness Partner to Marriott International Luxury Brands. She lives in Santa Barbara, California.
Woman intermittent fasting picking up some fruit

Image by Ani Dimi / Stocksy

While there are plenty of approaches to nutrition that will result in weight loss, there aren’t many that can improve your physical performance, cognitive function and workout recovery all at the same time. I have tried many different types of diets and lifestyle changes in an attempt to feel and perform at my best, but nothing has worked better than sticking to an eight-hour eating window—aka intermittent fasting.

Believe it or not, we have the ability to change the chemistry of our cells to create the cleanest energy, rapid repair, and better physical and mental outcomes. The best possible way to do this is, I’ve found, is fasting for 16 hours. It allows the body and mind to go into rapid cellular cleanup mode, and shifts the body from burning glucose (sugar) for fuel to burning ketones (fat), resulting in long-lasting energy. This process dramatically changes our performance during our workouts as well as our physique. Here are some of the benefits I’ve reaped by intermittent fasting (that you can experience too!).

1. I have more energy than ever.

In order for us to reach our potential during our workouts and workdays, we need to calibrate energy from the cleanest source possible. For the body and mind this is ATP (an energy molecule), since it’s converted much more efficiently in the body than glucose (sugar). In order to use ATP instead of glucose, we have to give our mitochondria a break from constantly being taxed by digestion and stress.

Intermittent fasting has totally changed my energy levels, from the second I wake up until the moment I go to sleep. Like I said, fasting for 16 hours gives my cells a break— which means I have more energy during my workouts without that fatigue-like crash afterward (or even at the end of my day). If you feel like you’re not able to give it your all during a workout or you really feel that afternoon slump, fasting is likely a good option for you.

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2. I recover faster from my workouts.

Inflammation can be a positive byproduct of exercise, allowing for muscular adaptations to take place. But if it becomes chronic, typically from stress, sugar, and environmental toxins, inflammation can create issues. This type of inflammation hinders our performance during a workout, as well as the results.

Intermittent fasting efficiently clears waste and toxins from the cells, allowing for a dramatic reduction in inflammation. This means you’ll spend less time feeling sore and fatigued and more time feeling energized and ready for more. And who doesn’t want that, right?

3. It's enhanced my physique—and given me lasting results. 

As I mentioned, intermittent fasting can speed weight loss by burning the body’s fat stores for fuel—a process called ketosis. During the 16-hour fast, the body burns through the glycogen in the liver, which elevates our metabolic rate. According to a study from the American Journal of Clinical Nutrition, subjects who ate the same number of calories as they would in a normal day—but in a smaller window of time—had a “significant modification of body composition, including reductions in fat mass.” Pretty crazy, right? 

Also, intermittent fasting boosts irisin—a molecule that makes our white fat cells behave like brown fat cells. This is important because brown fat cells protect the organs while white fat cells accumulate around the stomach, thighs and hips. The more we can activate brown fat cells the better—and the longer our physique and health benefits will last.

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4. My sleep improved immensely.

Lastly, intermittent fasting helps to balance cortisol (a stress hormone). Cortisol is supposed to rise and fall throughout the day, eventually coming down at night. Due to our action-packed lifestyles, cortisol tends to stay high all the way through the evening. This has negative consequences on our hormone balance and sleep patterns. (Insomnia, anyone?)

When cortisol is high, it tends to pull from the thyroid and our estrogen and testosterone stores, which can cause our metabolism to slow down. Additionally, high cortisol interrupts the body’s natural production of melatonin. This means we’ll have issues falling asleep, and we won’t get any of the deep sleep necessary to repair our bodies after a long workout (or even a particularly tough day). Fasting for 16 hours balances my cortisol, and now I never have these issues!

Ready to start crushing your fitness goals and have more energy? Check out mbg’s guide to intermittent fasting or if you’re a morning workout person, read more about how to make IF work for you.

Ready to learn more about how to unlock the power of food to heal your body, prevent disease & achieve optimal health? Register now for our FREE web class with nutrition expert Kelly LeVeque.

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