The weight loss industry is, quite frankly, a mess of spaghetti wires. You’ve got people recommending you do this and that, encouraging eating and fasting more or less of a food item, urging you to prioritize working out with more or less intensity, and so on. And that’s kind of understandable—our bodies differ from one another, and as such, our needs differ too!

However, this can be kind of tricky because two pieces of advice may not be as effective when done together. One notable example is fasting and working out. Both have health benefits in their own right, but is it possible to do both at the same time?

Let’s take a closer look.

Is It Okay to Work Out While Fasting?

The simple answer is yes, but with conditions. For the most part, working out and fasting at the same time is A-okay if you were already healthy to begin with. However, if you have any underlying conditions that make it hard to do both, then it’s probably better for you to not push yourself. We will be discussing this in the next section.

Additionally, you need to make some compromises. You’re unlikely to work out to your fullest potential if you’re fasting, simply because you don’t have as many calories to work with. So, you’re probably not going to run a full marathon if you fast, but 30 minutes of a brisk walk is perfectly fine.

Who Shouldn’t Work Out While Fasting?

Several people are highly discouraged from fasting.

The first group is people with coronary heart disease. This makes them prone to dangerous cardiac events when their heart rate goes way up. Since fasting makes exercising even harder, they can become more susceptible to cardiac events.

On the other end of the spectrum, you’ve got people with high blood pressure who need to take beta-blockers. This medication makes it hard for the heart rate to pick up. They could exercise loads and not get their heart rate up, making them use more calories than is necessary.

Lastly, there are diabetics. When fasting and exercising at the same time, they become more prone to hypoglycemia, or low blood sugar levels. Diabetics can easily become faint or dizzy when they exercise, so it’s important to eat well before, after, and sometimes even during workouts to prevent injury.

What Kinds of Fasting Should You Not Do While Working Out?

There are several kinds of fasting you should not do while exercising.

The first is any fast that lasts more than 24 hours. If you fast this long, your body will not have any glycogen stores to fuel your workout. You’ll probably feel very faint, and you’d just be pushing yourself harder than is necessary.

The second is any fast that’s lower than your daily recommended intake of calories. While a calorie deficit is important for losing weight, too much of it can send your body into starvation mode. This is when your body saves as much fat and energy as it can because it thinks food isn’t accessible.

Lastly, fasts that have you drinking only fluids (juice cleanse) or drinking no fluids (water fast) are also discouraged. Your body needs both food and fluids to work out.

Tips for Working Out While Fasting

Many things can go wrong if you fast and exercise improperly. Follow these tips to safely work out while fasting.

1. Go For Lower Intensity Workouts

Your body’s already running at half capacity. The last thing you want to do is expend all of that energy working out and not leaving some for everyday activities like sleeping and walking around the house. If you still insist on doing it, you’ll find that you’re more easily fatigued and prone to mood swings because of the lack of calories in your system (because you’ve already burned them)!

2. Go For Shorter Workouts

Understandably, you can’t work out as long as you normally would when fasting. You can’t expect a car with a half-full gas tank to run as far as the same car with a full tank! So, if you typically work 30 to 45 minutes on a normal eating schedule, aim for 30 minutes. You can choose to extend it to the end of 30 minutes if you feel like you can.

3. Exercise Before Your Fast

You should always exercise before your fast as this is when your body has the most food to work with. Working out at the tail-end of your fast is a no-go since your body will attempt to get energy from food that isn’t there.

4. Stop Exercising When Getting Warning Signs

Exercising never is easy, but know when your body’s having too much of a hard time exercising. Racing heartbeats and sweating are normal, but feeling faint and wanting to puke is not. It’s best to pause your workout to catch a breather lest you injure yourself. Eat a little snack to satiate your stomach, then go back to working out once you feel better.

5. Drink Plenty of Water

When you exercise, your internal temperature rises. This leads you to sweat out of your skin, making you lose body fluids in the process. You must keep replenishing your supply as water helps distribute nutrients to the muscles around your body. It is also important for repairing micro tears when you exercise—if you don’t drink water, you might just wake up super sore the next day!