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

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

intermittent fasting and working out

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 a part of the key to 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!

Intermittent Fasting According To The Age 

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 every day, and the rest of 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 from a certain time of day till a certain time in 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 by many 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 enjoy the results they get. If you have decided to give this weight loss approach a try, you should first consult your doctor to make sure you can do it safely (11, 12).

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intermittent fasting and working out in the morning
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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 breaking down your muscle mass for energy when it can’t get it from food you ate. People who combine intermittent fasting and working out may suffer from lack of energy and it could be 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.

working out and intermittent fasting
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Intermittent Fasting And Working Out: Pros And Cons

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

Pros:

  • You May Peel Off Unwanted Pounds

During your fasting days (or hours) your body is most likely to use its glycogen stores for energy. When those are depleted, it starts burning body fat to get energy and fuel (6).

According to one meta-analysis, people who exercise during fasting tend to burn more fat during exercise 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 worked out in a fasted state didn’t have better weight loss results over time than those who had a meal before training sessions (2).

intermittent fasting and working out for 6 weeks
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  • It Has Anti-Aging Effect

According to one review, by combining intermittent fasting and physical exercises, one may be able 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 possibly caused by this combination, although the research in this area is still at an early stage (5).

  • You May Boost The Autophagy Process

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

Read More: How To Make Fasting Easier: Tips That’ll Come In Handy Even For Seasoned Fasters

Cons:

  • It Might Be Harder To Build Muscles

According to studies, people who stick to intermittent fasting may gain less muscle mass than those who stick to a regular eating pattern without calorie restriction. However, they may retain more muscle mass than those who restrict their calories every day (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 research, exercise without adequate fuel can cause poorer performance, especially among trained athletes (9).

intermittent fasting and working out at night
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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 or other electrolyte-containing beverages may help to replenish the electrolyte levels of your body, you’ll just want to avoid those with sugar if you are fasting.
  • Take into consideration the type of fasting. The longer you are fasting, the lower the intensity of your exercises should be.
  • 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 may be better to do it during your eating window and then eat high protein meals afterward to preserve and help build your muscle mass.
  • Always discuss your plans with your doctor.

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.

keto intermittent fasting and working out
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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 may also be better to perform your exercises at the end of your fasting period, so you can eat afterwards. At first it will be a little hard to exercise after a long non-eating period, but you’ll get used to it. You can adjust the intensity of your workout to match how your body is feeling.

  • Intermittent Fasting And Working Out At Night

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

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FAQs

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.

intermittent fasting and working out for men
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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 rules concerning the foods you eat during your eating window, you still should be aware. If you want to lose weight and support your health, it is better to opt for nutritious foods. Fruits and veggies, lean cuts of meat, whole grains, 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 dietitian (that will be better) to figure this out.

Keto Intermittent Fasting And Working Out: Is It Possible?

Basically, the recommendations are the same as for regular intermittent fasting diet. However, you should combine the keto and intermittent fasting diets with caution. You shouldn’t begin both weight loss approaches at the same time, as such serious changes in your lifestyle are a great stress for your body. This needs at least several weeks to get used to such adjustments. First, you should introduce the keto diet, and then – intermittent fasting. In this way your body gradually adapts to the changes in your nutrition.

If you feel fatigue, nausea, dizziness, mental fog or suffer from injuries, it is better to break your diet and talk to your doctor. The same thing goes if you need a lot of time to recover after your training sessions. It is a great challenge for your body not to get fuel for a long period of time and not to get some food groups because of the keto diet. In combination with workouts, this can lead to some health issues.

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Conclusion

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.

DISCLAIMER:

This article is intended for general informational purposes only and does not address individual circumstances. It is not a substitute for professional advice or help and should not be relied on to make decisions of any kind. Any action you take upon the information presented in this article is strictly at your own risk and responsibility!

SOURCES:

  1. Autophagy: Everything you need to know (2020, medicalnewstoday.com)
  2. Body composition changes associated with fasted versus non-fasted aerobic exercise (2014, jissn.biomedcentral.com)
  3. Can you workout while doing an intermittent fast? (2020, medicalnewstoday.com)
  4. Effects of aerobic exercise performed in fasted v. fed state on fat and carbohydrate metabolism in adults: a systematic review and meta-analysis (2016, cambridge.org)
  5. Exercise, fasting, and mimetics: toward beneficial combinations? (2016, faseb.onlinelibrary.wiley.com)
  6. Exercising in the Fasted State Reduced 24-Hour Energy Intake in Active Male Adults (2016, ncbi.nlm.nih.gov)
  7. Flipping the Metabolic Switch: Understanding and Applying Health Benefits of Fasting (2017, ncbi.nlm.nih.gov)
  8. Intermittent versus daily calorie restriction: which diet regimen is more effective for weight loss? (2011, onlinelibrary.wiley.com)
  9. International society of sports nutrition position stand: nutrient timing (2017, pubmed.ncbi.nlm.nih.gov)
  10. Time-restricted feeding in young men performing resistance training: A randomized controlled trial timing (2017, pubmed.ncbi.nlm.nih.gov)
  11. What Is Intermittent Fasting? (2021, verywellfit.com)
  12. What to Expect When Intermittent Fasting (2020, verywellfit.com)
  13. Working Out While Intermittent Fasting (n.d., prospectmedical.com)
See also  Runner’s Diet To Lose Weight: Nutrition Tips For Those Who Enjoy Logging Miles On A Treadmill
L. Woods
L. Woods

Lana is an excellent writer driven largely by questions of health and mental well-being. She specializes in writing articles on both nutrition and exercise. Nothing brings her as much pleasure as helping others get their health back on track. In her works, she provides informative tips on how you can change your lifestyle for the better, develop healthy eating habits, and improve your well-being with the help of workouts. Besides, in recent years she became more interested in studying weight management, gearing her focus towards healthy weight loss approaches.

K. Fleming
K. Fleming

I am a U.S. educated and trained Registered Dietitian (MS, RD, CNSC) with clinical and international development experience. I have experience conducting systematic reviews and evaluating the scientific literature both as a graduate student and later to inform my own evidence-based practice as an RD. I am currently based in Lusaka, Zambia after my Peace Corps service was cut short due to the COVID-19 pandemic and looking for some meaningful work to do as I figure out next steps. This would be my first freelance project, but I am a diligent worker and quite used to independent and self-motivated work.

Kristen Fleming, MS, RD, CNSC

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