Is It Bad To Train On An Empty Stomach?

Everything you should know about fasted workouts

We’ve all been told pretty much the same thing: you need to eat before you workout! Along with other nutrition and health mantras such as it’s important to fuel your body. Recently, however, there has been a relatively new nutrition trend that has come in on the coattails of the intermittent fasting craze which is fasted workouts. 

Now fasted workouts is just a fancy term for working out on an empty stomach. The most common practice is to wake up in the morning and head straight to the gym. No carbs, no protein shakes, no nothin’. So what’s the deal? Is it truly better to hit the gym with no food in your stomach, or is all the good old health advice still true that we need to feed ourselves before we exercise?

So if you have ever been curious about the answer to these questions you are at the right place! Read on to find out about the pros and cons of working out on an empty stomach.

What Is ‘Fasted Exercise’? 

The logic behind working out hungry being a good idea is pretty straight forward. Essentially the notion is that you will have increased fat burn if you exercise on an empty stomach. This idea comes from the fact that you have depleted glycogen stores AKA stored up carbohydrates that give you energy in your system and if you exercise your body will be forced to burn fat for energy. So, if you have an empty stomach and you go on a run, for example, your body will use fat as fuel and not your carb storage.

These fasted workouts do have some scientific research to back it up too. In fact, a 2013 study published in the British Journal of Nutrition concluded that working out on an empty stomach, or fasted, burned nearly 20% more fat than doing so after breakfast.

What Are The Other Benefits To Fasting? 

Beyond working out on an empty stomach, maintaining a fasted state, which is defined as not eating for about 14-16 hours, has proven to have other very compelling health benefits. Here are few that have some solid scientific evidence to back them up.

Fasting’s Effect On Growth Hormones

The second reason, which comes down to growth hormone (GH), is that a good old-fashioned fast can promote muscle gain and fat loss. GH is 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 percent and 1,300 percent in womenThe effect ends when the fast does, which is a compelling reason to fast regularly in order to keep muscle-friendly hormones at their highest levels.

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Fasting’s Effect On Insulin 

Fasting improves 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 poor insulin sensitivity ups the risk of heart disease and cancer and 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. This in turn that makes it easier to lose fat, improves blood flow to muscles and even curbs the impact of an unhealthy diet.

The Negative Impact Of Fasted Workouts

Although fasting has shown to have great benefits for some people in certain circumstances it is also important to recognize that fasting isn’t always a magic bullet. This is especially true if you are considering working out on an empty stomach. We’ve collected some of the drawbacks oo exercising without eating and why it’s important to listen to your body and tailor to your needs. 

Muscle Damage

Though many studies have found that working out in a fasted state has its benefits, there are also some drawbacks to be aware of. Skip breakfast and heading to the gym doesn’t mean you are guaranteed any miracle results. This is especially true if you are training yourself particularly hard.

Because if you do push yourself on an empty stomach you are running the risk of your body eating up your muscle tissue as a source of energy. Studies have shown that doing a regular exercise routine at your normal intensity would not cause you to tap into muscle mass for added energy. But if your goal is to amp up the intensity of your workouts then fasting might not be your best option.

Another thing to consider along with the depletion of your muscle mass being damaging to your physique is the negative impacts on your metabolism as well. This is due to the fact that the rate of your metabolism is more or less dictated by the amount of muscle mass your body has. Meaning that the more muscle the higher your metabolism and the less muscle the lower your metabolism. So by using muscle tissue as a source of energy your body effectively lowers its overall metabolic rate. Not great news if you would like to either build muscle or lose fat. 

Lower Energy

Another downside to exercising fasted is that you’ll simply have less energy to push yourself harder. A study published in the Journal of Science and Medicine in Sport, which studied both men and women, showed that fasted exercise decreased performance when the subjects worked out on an empty stomach. 

A 2014 study in the Journal of the International Society of Sports Nutrition looked at the results of fasted cardio over a much longer period of time. After a month, researchers found no difference in body composition (in terms of weight, body fat percentage, waist measurements, etc.) between members of groups that ate before exercising and those that ran on an empty stomach.

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How Should You Fuel Your Body Before A Workout? 

Some fuel is better than no fuel, so don’t stress too much about the numbers and listen to your body. If you’re looking to really optimize your workout, you’d want to eat something high in carbohydrates before your workout. This increases your energy levels during exercise, which you might need if you’re feeling groggy, as it will you to exercise at higher intensity levels.

To reduce any nausea or other unwanted gastrointestinal symptoms you should eat something low in fat and fiber, that your body can digest quickly. The following can all be great breakfast options:

  • Peanut butter & jelly on whole-wheat bread
  • Oatmeal with fruit and walnuts
  • Banana and toast
  • Greek yogurt
  • An egg on an English muffin

All of these food combinations would provide that carb-y energy kick that you need for your regular morning workout, without making you want to barf mid-burpee. However, if your workout is on the intense side (like, if you’re training for a marathon and completing a long training run), then your body would need slightly more fuel before, during, and after.

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Lesley George

Lesley is a content writer and community manager at Shape.
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