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Should You Fast Before a Workout?

by Emily S. · September 08, 2019 · 2 minute read
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You may think that consuming a snack before a workout is a must, but is that actually the case? The answer depends on your goals. Research has found that there are significant health benefits to exercising in a fasted state. Even better, if can lead to neuron and muscle regeneration.

So what are you burning?

When you exercise after having a snack, or when there is glycogen stored in your body (like after a meal), your body uses that fuel for energy. But when you exercise in a fasted state, your body is forced to use its “reserves”. Reserves are fats stored in the body. Research shows that exercising of a fasted state increases acute oxidative stress. This refers to a state in which your muscles produce glutathione and superoxide dismutase mitochondria (one of those crazy little antioxidants the body produces to fight off the bad stuff). As a result, your muscles become increasingly resilient to stress and function better.

But it’s not just for your muscles. Exercising in a fasted state also triggers an increase in growth factors such as brain-derived neurotropic factor (BDNF) and muscle regulatory factors (MRFs) in both men and women. These can increase cognitive function and stimulate the creation of new neurons and muscle cells. It can even stimulate healing by the burning and regeneration of damaged cells, a process known as autophagy. Essentially, your body uses existing resources to burn the bad stuff, and stimulates regeneration of newer, healthier cells. That being said, both sources of fuel serve a purpose. The ability to switch between the two sources of fuel is key to lasting fitness success, performance, or weight loss.

So what’s your goal?

Every body is different, and processes fuel differently based on a variety of factors like sleep, diet, genetics, and more. But if your goal is exercise for the purpose of losing weight, working out in a fasted state may be preferred. If you are an athlete training for optimum performance in competition, research shows that competing fed (with glycogen as a source of fuel) leads to best results. However, training in a fasted can also improve your body’s ability to switch between the sources of fuel even if you’re an athlete.

So how flexible are you?

One of the key factors in successfully losing weight and keeping it off is metabolic flexibility. Metabolic flexibility refers to your body’s way of using the fuel you put in. It also refers to the ease with which your metabolism and switch between using carbs or fats as a source of fuel. If you have great metabolic flexibility, your body’s ability to process the foods you eat is greatly improved. Focusing on metabolic flexibility is the path for sustained fitness optimization, rather than extreme and unsustainable diets.

So will you try working out in a fasted state?

Emily S. picture

Emily S.

Emily is a marketing and communications specialist and a former elite level figure skater.