The Conscious Gut

Intermittent Fasting And Working Out: Here’s What Science Actually Says About This Combo

The modern wellness world boasts an impressive number of various meal plans that can help you to achieve your fitness goals. Intermittent fasting has become one of the most common diets that continues gaining popularity thanks to its relative simplicity. But it is a well-known fact that a proper eating pattern is only 50 percent of your success. To optimize your results, it is critical to combine a healthy meal plan with regular physical exercises. But is this scheme suitable for every diet? Is intermittent fasting compatible with working out? Will it be safe for your overall health? Take a read through the article to find the answers. Let’s start!

A Short Guide To Intermittent Fasting

Intermittent fasting is quite a popular meal plan and its premise is rather obvious – that dieters have to fast during certain periods of time. This depends on the intermittent fasting variation they opt for. Some people prefer 5:2 fasting (fasting only for 2 days of the week), others fast only for 1-3 days per month. The concept 16:8 is one of the most common. Basically, you should eat all your meals during an 8-hour window, and the rest for the 16 hours are for fasting. This variation is quite popular, as these 16 hours usually include the time when you sleep. You skip your breakfast and can eat at the time of day till the evening.

There are no special food lists of what you should or shouldn’t consume, your meal plan is totally up to you. However, if you have started fasting in order to lose weight, it is important to make healthy eating choices and practice portion control. Only in this way you’ll be able to lose or maintain healthy weight. Besides this, your body has its nutritional needs and your daily menu should help you supply your body with all the necessary nutrients.

This weight loss approach is considered to be an effective way to fight obesity and cut the calorie intake for a prolonged period of time. However, there are also some drawbacks. For instance, some people can face overeating or binge-eating during the non-fasting period. Many people also tend to opt for unhealthy foods during their non-fasting period.

The intermittent fasting method needs more scientific backing concerning its effect and safety. Despite this fact, many people still choose it for dieting and enjoying the results they get. If you have decided to give this weight loss approach a try, you should consult your doctor (11, 12).

Can I Work Out While Intermittent Fasting?

So, as you have understood, the main idea is not to eat for quite a long period of time. You also know that your body needs fuel for any activity, especially for workouts. The question is – is it possible to combine intermittent fasting and working out with no harm for your health?

The information concerning this issue is quite controversial. It is important to take into consideration such factors as your overall health condition, fitness level, age, lifestyle and eating habits. That is why the consultation of a health professional is needed.

First, for those people whose priority is working out, they should opt for a diet that will provide their bodies with fuel. Physical exercising is a stress for your body, and if it doesn’t get necessary amounts of food, this stress becomes even stronger. There is also a possibility that because of lack of fuel your body might start using your muscle mass instead of from food you ate. People who combine intermittent fasting and working out, suffer from lack of energy and it’s harder for them to perform their exercises. Slowed metabolic rate is possible as well.

However, there are also positive aspects, such as burning more body fat and weight loss. Let’s see all the risks and benefits of intermittent fasting and working out combination.

Intermittent Fasting And Working Out: Pros And Cons

Below you can see advantages and disadvantages of combining intermittent fasting and working out (3).


  • You May Peel Off Unwanted Pounds

During your fasting days your body is most likely to lose its glycogen stores. That’s why it starts burning body fat to get energy and fuel (6).

According to the study, people who exercise during fasting tend to lose more body fat than those who work out after having a meal (4).

However, the facts concerning the effect on weight loss are rather controversial.

Another study has shown that the individuals who both fasted and worked out didn’t have better weight loss results than those who had a meal before the training session (2).

  • It Has Anti-Aging Effect

According to a study, by combining intermittent fasting and physical exercises, one can slow down the processes of aging and lower the risks of diseases. Such an effect is achieved thanks to the changes in metabolism which are caused by this combination (5).

  • You May Boost The Autophagy Process

This is a process in your body, that helps to get rid of damaged body cells and create healthy ones. According to a research, the combination of intermittent fasting and exercising can boost this process (1, 7).


  • It Might Be Harder To Build Muscles

According to the studies, people who stick to intermittent fasting gain less muscle mass than those who stick to a regular eating pattern. However, they still can maintain necessary muscle mass (8, 10).

  • It Affects Your Blood Sugar Levels And Blood Pressure

Working out while intermittent fasting can decrease your blood sugar levels. Too low a level of blood sugar can cause fainting. You may also face low blood pressure and experience lightheadedness.

  • It Might Lead To Poor Performance

According to a research, such a combination can cause poorer performance, especially among trained athletes (9).

How To Work Out While Fasting: Tips For Your Success And Safety

Here are some tips that will help you stay healthy and reach you fitness goals (3):

  • If you are a newbie, it is better to opt for low-intensity types of workouts. In this way you won’t lack that much energy.
  • It is critical to be attentive to what your body is trying to tell you. This is important, as you may start feeling bad during your training sessions. If you are attentive to yourself, you’ll avoid injuries and a number of health issues.
  • It is vital to stay hydrated all the time – during your fasting period, eating-windows and training sessions. In this way you’ll replace the fluids your body loses during exercising. Drink even more water on your fasting-days. By the way, some coconut water may help to replenish the electrolyte levels of your body.
  • Take into consideration the type of fasting. The longer you are fasting, the lower the intensity of your exercises should be.
  • Pay attention to your nutrition after working out. Make sure you eat enough protein and carbs.
  • Pay attention to the link between your workouts and macronutrients. For instance, if you opt for strength training, your body will need more carbs. High intensity interval training and other cardio workouts need less carbs.
  • If you opt for lifting weights, it is better to do it during your eating window and then eat high protein meals to preserve your muscle mass.

What Are The Best Exercises On Intermittent Fasting?

In this case everything depends on the intermittent fasting variation you choose. If you opt for a 16:8 diet, you can choose both strength and cardio exercises. However, if you want to try alternate day or 24-hour fasting and keep training during the fasting days, it is better to opt for less intensive workouts. Yoga and pilates will be a nice option. Walking is Ok as well.

When Is It Better To Work Out On Intermittent Fasting?

  • Intermittent Fasting And Working Out In The Morning

This is most likely the best option, as in this way you’ll support your circadian rhythm. It is also better to perform your exercises at the end of your fasting period. At first it will be a little hard to exercise after a long non-eating period, but you’ll get used to it.

  • Intermittent Fasting And Working Out At Night

Training sessions too close to the time you go to bed are undesirable, as they will decrease the quality of your sleep (13).


How Long Can I Work Out On Intermittent Fasting?

There are no clear recommendations concerning this issue. Everything depends on your fitness level, the type of workouts and intermittent fasting you choose. However, if you feel lightheaded or dizzy during your training session, it is recommended to take a break.

What Is It Better To Eat After A Training Session To Break A Fast?

While sticking to the intermittent fasting diet, people usually eat less food. This is why it is critical to make the meals you consume during your non-fasting period super-nutritious and healthy. Although there are no certain restrictions concerning the foods you eat on your eating window, you still should be careful. If you want to lose weight and support your health, it is better to opt for whole and unprocessed foods. Fruits and veggies, lean cuts of meat, nutritious smoothies and other healthy foods will be the best choice. To grow and recover, your muscles need protein and carbs. Your calories and their amount depends on numerous factors including your fitness goals. You can use online calculators or talk to a registered dietician (that will be better) to figure this out.


As you can see, the intermittent fasting and working out can work together. However, you should be very careful when timing and choosing the type of your workouts. Make sure they aren’t too hard for you and you feel Ok. Don’t forget to opt for healthy foods, that will refuel your body and support its proper functioning. Perform your exercises safely and properly, choose them taking into account your fitness level and be attentive to your body. Make it a rule to hydrate your body as much as possible in proper amounts. Healthy high quality sleep is crucial not only for your health, but for your weight loss goals as well. It is also vital to talk with your healthcare professional before you start your intermittent fasting journey and choose some workouts. Take care of yourself and stay healthy.

Alexandra Danieli

Alexandra Danieli, CHC, The Conscious Gut
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