Should You Be Exercising On An Empty Stomach?

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ExerciseOnEmptyStomach_Slide1Illustrated by Daniel Koppich.
It’s a debate that’s raged since the first weight was lifted: Is it better or worse to work out on an empty stomach? It’s time for this madness to end. We have the final answer.

Well, not the final answer. Different people work out best under different circumstances, and deciding whether someone should eat before training can be like telling them what time of day to work out or which diet they should follow — it largely depends on what works best for the individual. But, it is time to dismantle some old myths.

Contrary to popular belief, research suggests that eating many small meals throughout the day won’t speed up the metabolism, skipping a meal won’t make you fat, and exercising on an empty stomach will not nullify a workout. In fact, skipping a meal or two, also known as “intermittent fasting” (IF), can be downright beneficial.

Optimizing Hormones (Fast)
If the fact that Hugh Jackman practiced intermittent fasting to gain muscle for his latest Wolverine movie isn’t convincing enough, consider this: An empty stomach triggers a cascade of hormonal changes throughout the body that are surprisingly conducive to both building muscle and burning fat.

The fasted state produces two significant effects. First, improved insulin sensitivity. Put very simply, the body releases insulin (a hormone) when we eat to help us absorb the nutrients from our food. The hormone then takes the sugars out of our bloodstream and directs them to the liver, muscles, and fat cells to be used as energy later on. The trouble is that eating too much and too often can make us more resistant to insulin’s effects, and while poor insulin sensitivity ups the risk of heart disease and cancer, it also makes it harder to lose body fat. Eating less frequently (i.e. fasting more regularly) is one way to help remedy the issue, because it results in the body releasing insulin less often, so we become more sensitive to it — and that makes it easier to lose fat, improves blood flow to muscles, and even curbs the impact of an unhealthy diet.

The second reason a good old-fashioned fast can promote muscle gain and fat loss comes down to growth hormone (GH), a magical elixir of a hormone that helps the body make new muscle tissue, burn fat, and improve bone quality, physical function, and longevity. Along with regular weight training and proper sleep, fasting is one of the best ways to increase the body’s GH: One study showed that 24 hours without food increases the male body’s GH production by 2,000%, and 1,300% in women. The effect ends when the fast does, which is a compelling reason to fast regularly to keep muscle-friendly hormones at their highest levels.

We can’t speak of muscle-friendly hormones without bringing up testosterone. Testosterone helps increase muscle mass and reduce body fat while also improving energy levels, boosting libido, and even combating depression and heart problems — in both men and women. Fasting alone may not have any effect on testosterone, but there is a surprisingly simple way to produce large amounts of both “T” and growth hormone at the same time, creating an optimal environment for building muscle and torching fat: exercising while fasting.
ExerciseOnEmptyStomach_Slide2Illustrated by Daniel Koppich.
The Fast Way To Improve Performance
Exercise, especially intense exercise that uses a lot of muscles (think compound movements like deadlifts and squats) causes a big surge in testosterone — which is why it can make good sense to combine exercise and fasting. Many studies have found that training in a fasted state is a terrific way to build lean mass and boost insulin sensitivity, not just because of the nifty hormonal responses, but also because it makes the body absorb the post-workout meal more efficiently.

In short, fasted training helps to ensure that carbs, protein, and fats go to the right places in the body and are stored only minimally as body fat. Exercising on an empty stomach has been shown to be especially great for fat loss, and it’s even been shown that people who train while fasted become progressively better at burning fat at higher levels of intensity (possibly because of an increase in fat-oxidizing enzymes).

Not interested in training like a bodybuilder? There are also potential benefits for endurance athletes, since fasted workouts can improve muscle glycogen storage efficiency. What that means, basically, is that running on empty can make the body better at using its energy stores. The occasional fasted training session can improve the quality of “fed” workouts (or races) later on. In a nutshell: When the body learns to exert itself without any food, it gets better at performing when it does have fuel in the tank. Some studies have also shown that fasted workouts can significantly improve endurance athletes’ VO2 Max, which measures a person’s capacity to take in and use oxygen during exercise and is a pretty decent way of measuring someone’s fitness.

Now, we would be remiss if we didn’t acknowledge that some studies have shown impaired performance as a result of fasted exercise. That said, many of these studies are of Ramadan fasts, which don’t allow the consumption of fluids (which is not advisable when engaging in athletic activities). Still, the prevalence of people who do eat before exercise is pretty good evidence that exercising after eating can work. Heck, there are even studies showing that eating before exercise can lead to fewer calories consumed throughout the day. But, that doesn’t discredit the evidence that fasted workouts, even if occasional, can reap a lot of benefits.
ExerciseOnEmptyStomach_Slide3Illustrated by Daniel Koppich.
So You Want To Fast Before Exercise? Your Action Plan
We know what you’re thinking: “I can’t handle intense exercise without food in my belly!” Firstly, give yourself a little credit! You’re capable of more than you think with the right frame of mind. Secondly, there are several tips you can follow to help you out with this new approach to eating.

You can consume more than just water. Feel free to quell cravings and get an energy boost with black coffee, plain tea, Branched Chain Amino Acids, creatine, or any kind of drink or supplement that’s virtually calorie-free. According to the leading experts on the subject, Brad Pilon and Martin Berkhan, even Diet Coke or sugar-free gum won’t break the fast (though, not recommended). Just check with a doctor before switching it up too quickly.

Break your fast whenever you'd like. A lot of people like their first meal right after exercising, since the fast improves the absorption of the post-workout meal, but it’s actually no big deal if the fast lasts for a while longer. Even if you exercise in the morning and don’t eat until the evening, the wave of growth hormone you’ll be riding all day should prevent muscle loss. However you decide to approach this, your body’s got you covered.

Eat as many meals as you'd like. Note: We didn't say as many calories as you like. But, it’s not necessary to eat many meals throughout the day. Despite some long-held myths that the body can only absorb a certain amount of protein at a time, we're completely capable of digesting the day's intake in one big meal (of course, this doesn’t mean that you need to!). Studies have shown that doing so results in no strength or muscle loss, and some have even shown that concentrating food intake into one or two meals each day can be a better way to build lean muscle mass. A lot of protein just takes longer to digest and be utilized, but it still gets digested. Even after eating a normal-sized meal, amino acids are still being released into the bloodstream and absorbed into the muscles five hours after eating. So play around with the feeding times and styles that work best for you.

The short of it: Metabolism and the digestive system are simply not as temperamental as some might believe.

The Takeaway
Eating is perhaps the most ingrained habit we have, and humans are truly creatures of habit. Disrupting that habit by skipping a meal or two can be profoundly difficult for some people (particularly those who have wrestled with disordered eating). It’s true that intermittent fasting takes some getting used to as the body learns not to expect food so frequently. That discomfort usually does pass, but if fasting just isn’t for you, then there’s no need to keep it up — just don’t be afraid to try it out. Intermittent fasting is just one approach to health and fitness, and certainly not the only one that can get you results.

“If fasting just isn’t for you, then there’s no need to keep it up — just don’t be afraid to try it out. ” But, myths and misconceptions do need to be dispelled, and this article is here to say this: In general, there is no need to eat before exercise. If you feel better when you do, then by all means, keep it up! However, if choking down a pre-workout banana or bowl of oatmeal is a dreary chore that you only do because it’s supposed to help you avoid muscle loss/fat gain/growing antlers, then it’s time to relax. You’re completely free to eat whenever you want. Just listen to your body — it’s got you taken care of.

Special thanks to Brad Pilon of Eat Stop Eat for his help with this article. Check out his Facebook and Twitter for more intermittent fasting tips.

Full disclosure: sometimes, we're lazy. So, whether it's seven ways to simplify our morning routine or how to make our time at the gym actually enjoyable, we're into it. And to keep us on track, we've turned to Greatist, because they've got us excited about staying fit — and having fun doing it.