Working out on an empty stomach: good or bad?

The Yard Athletics - Sam Shaw

By Henry Gould – May 29, 2018

Despite the huge advances in research surrounding health, nutrition and fitness, I can’t think of another industry that is still so plagued by junk pseudoscience. The dietary supplement industry in North America alone was estimated at $37+ billion in 2016, and since their sole objective is to sell you as many products as possible, keeping a skeptical mindset on any “miracle claims” or new products is likely a good idea.

Part of how the supplement industry can easily sell their products is by playing into human emotion and our pattern-seeking mentality. As the moderately intelligent mammals we are, we do our best to make sense of the world around us in order to better predict the future. Whether this is noticing that drinking from a dirty stream makes us sick, or that eating doughnuts tends to precede weight gain, we look for patterns in order to acquire knowledge that will help us survive long enough to pass on our genes.

Health and fitness myths are endless, and something I find fascinating. One idea in particular that I’ve always found interesting is the theory of working out on an empty stomach. The thinking is this: if you work out before you’ve had anything to eat, particularly in the morning, your body will tap into stored fuel reserves (glycogen in muscles, as well as fat) to power the workout, thus speeding up your metabolism and burning more body fat.

Right away this sounds perfectly logical, and almost seems to necessitate no further inquiry. Why wouldn’t this be true?? Surely when you’ve been fasting all night, the body has to tap into all that stored glycogen and fat in order to power through the deadlifts?

Apparently it’s not that simple. Although the body uses two main sources of energy to power every biological process (glucose from stored glycogen, ketones from stored fat) just because you workout on an empty stomach doesn’t mean the body automatically taps into the fat. A lot can vary on body type, as well as overall body mass, but because glucose is the bodies main source of energy, typically it will tap into the glycogen stored in muscles to supply energy for a workout rather than stored fat. Glycogen is much easier to replace following a meal, whereas the body wants to keep and store fat as an emergency fuel source, as well as to keep us warm.

Remember, the body doesn’t know we live in a world with unlimited access to food, warm clothes and housing. When presented with an abundance of food, the body instinctively wants to overeat as it doesn’t know when it might get another meal, and consequently, will store a lot of the over-eaten food as fat in order to preserve it for later.

Below are a few articles I found interesting on the subject, so have a read through and see what you think. Ultimately, exercise on an empty stomach is likely never a bad thing (so long as there’s a meal nearby in the future), but listen to your body and expect that the first few times doing so may feel more sluggish than others, as the metabolism adjusts to the demands being put on it.

Men’s Health – “Should You Work Out On An Empty Stomach?”

Livestrong – “Should I Excercise While Fasting?”

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