Intermittent Fasting and Working Out |

For many, the intermittent fasting (IF) diet is a novel and thought-provoking way to lose weight. But what does it mean from a practical perspective?

intermittent fasting (IF) is a growing trend for those who want to lose weight, feel energized, and maintain a healthy lifestyle. While some people do it to bypass their daily food intake in order to achieve a certain goal, others do it to lose weight.

With the holiday season fast approaching, people are busy planning parties and setting goals for their New Year’s Resolutions. If you’re not one of those fortunate people, you can still take advantage of these opportunities to improve your life, with the help of intermittent fasting (IF).

Chapter 7

Fasting and exercise on a regular basis

Because fasting and exercise are both stressors, they don’t often go together. We’ll look at what science has to say about intermittent fasting and exercise, how to match your workout plan with your fasting schedule, and when to undertake low-, high-, and active-recovery exercises in this chapter. 

Important ideas

  • It matters how you workout. Moderate exercise combined with intermittent fasting has been shown to be more effective than either no exercise or severe activity.
  • Your body will react by reducing spontaneous activity if your body weight falls too low or your negative energy balance becomes too extreme. In other words, resting on the couch becomes the most appealing alternative.
  • Several things influence your ability to perform while fasting. Your genetics, your fasting schedule, the type of activity you do, and your recovery are all factors to consider.

We’ll simply come out and say it because there’s no way around it.

Your exercise performance will most certainly suffer—at least temporarily—depending on the intermittent fasting (IF) regimen you follow.

The good news is that you don’t have to quit exercising. To reach your goals, all you have to do is locate your sweet spot—that magical location where you’re working out “just enough” and fasting “just enough.”

In this chapter, we’ll show you how to get there using a road map. You’ll discover:

What can we learn about intermittent fasting from Ramadan?

Observant Muslims fast every day from dawn to sunset for around 30 days during the holy month of Ramadan. A large dinner is frequently served as a fast-breaking evening meal.

Researchers have been studying faithful Muslims for years to see how fasting affects a variety of outcomes, including sports performance. According to study, Muslim athletes perform poorly in the first few weeks of a Ramadan fasting program. 1

Several things influence how well someone performs:

  • The individual sportsperson: Some athletes adapt to fasting more easily and quickly than others, just as some athletes can exercise harder and longer than others. Greetings, genetics.
  • Recovery and nutrition: Getting enough rest, sleep, water, and nutrition can all help the body adjust to IF and heavy exercise more rapidly.
  • The fasting schedule is as follows: Fasting that is less intensive (such as the 16:8 routine) works better with hard activity than fasting that is more rigorous.
  • The type of workout. Fasting is more likely to have a negative impact on high-intensity training. (More on this later.)

The activities listed below don’t usually go well with IF. If any of these are your thing, your performance will most likely suffer as your body adjusts to this new way of eating:

  • tasks that need a lot of effort (such as 200-400 meter runs)
  • In soccer, for example, speed endurance is demonstrated through repeated short, intense runs.
  • jumping, jumping, jumping, jumping, jumping, jumping, jumping, jumping, jumping, jumping, jumping, jumping, jumping
  • some sorts of job capability and strength

You could realize that you can’t run or cycle up hills as well as you used to. You might not be able to do as many push-ups or pull-ups if you strength train.

Worse, if you try to push through, your body will almost certainly punish you in other ways. When co-founder John Berardi, PhD, combined twice-weekly fasting with a moderate exercise regimen, he found himself exhausted by mid-afternoon.

“It’s like I’m a video game character that starts off with 10/10 on the power meter and by late evening there are just three bars left,” Dr. Berardi explained.

Why? He stayed on the couch because his body was conserving calories. He couldn’t neutralize his negative energy balance unless he forced himself to get up and do something.

But it’s not all doom and gloom.

Combining exercise and IF can also help you achieve better outcomes.

One study examined how people fared when they tried alternate day fasting (ADF) with or without exercise. 2 The following are the effects of exercise (or lack thereof) on heart health (as measured by LDL cholesterol is a kind of cholesterol that is found in levels), body fat, and lean mass (muscle, bone, connective tissue, and internal organs):

  LDL cholesterol Fat mass Lean mass
Without exercise, ADF 1 point was deducted. 4.4 lb/2 kg weight loss 2.2 lb/1 kg weight loss
With exercise, ADF 12 points were deducted. I lost 11 pound and 5 kg. 0 lb/0 kg weight loss

However, to see results, you must strike a balance: enough movement to maintain lean mass but not so much that you don’t recover.

Use the following hints to reach that elusive equilibrium.

Pointer #1: Any intermittent fasting regimen should be paired with low-intensity activity.

Our forefathers did not put themselves through torturous training sessions. In reality, they desired to conserve essential energy and remain injury-free for as long as possible.

The majority of their activity consisted of rambling, such as strolling, which is ideal for IF. That is to say:

  • Maintain your current level of exercise when experimenting with IF fasting patterns if you aren’t already doing so.
  • If you’re currently exercising vigorously, consider lowering or eliminating high-intensity training in favor of more rambling-type movement in your daily life.

Pointer #2: If you’re on a strict fasting schedule, reduce the intensity of your workouts.

Krista Scott-Dixon, PhD, the Director of Curriculum at, learned this lesson the hard way when she began fasting twice a week. Because she was under pressure to lose weight for upcoming Brazilian jiu-jitsu contests, she kept her workouts quite intense.

She explains, “I was riding and jogging several hours a week, often when fasted.” “I imagined myself to be a badass. In reality, I was being a fool and doing exactly what I warned my clients against.”

She had insomnia, heart palpitations, anxiety, and terrible mood swings, as well as stress fractures in the making.

Let her story serve as a warning.

It’s easy to delude ourselves into believing we’ll be the exception. All too frequently, we discover that we are the exception rather than the rule.

It’s up to you to decide what constitutes “too much” exercise, but a decent general rule of thumb is:

  • Heavy weight training should be limited to 3-4 hours per week.
  • During the week, no more than 2-3 quick metabolic conditioning activities are recommended (intervals, high-intensity cardio, circuit training)
  • Moderate-intensity cardio for no more than 1-2 hours each week (if any)

(See “How to Avoid Overtraining” for further information.)

Pointer #3: Plan your meals around your workouts.

There is no one optimum way to organize fasting and non-fasting periods, as you’ll see throughout this booklet. Pointer #4: Self-experimentation can help you figure out what works best for you.

Most people, on the other hand, find that doing out on days when they are better fed works best for them. It gives them ample energy for workouts while also providing nutrients for recovery.

The “intermittent” element of IF can be more successful than a typical caloric deficit in this regard.

For example, if you were to limit calories by 75% three days a week and eat regularly the other four, your training routine may look like this:

  Intake of energy Type of activity
Day 1 Low-cost (0 to 25 percent of normal needs) Active recovery or low-intensity recovery (e.g. gentle yoga, walking, mobility exercises)
Day 2 Typical (100 percent of normal energy needs) Longer duration or higher intensity (e.g. weightlifting, metabolic conditioning, long runs)
Day 3 Low-cost (0 to 25 percent of normal needs) Active recovery or low-intensity recovery
Day 4 Typical (100 percent of normal energy needs) Longer duration or higher intensity
Day 5 Low-cost (0 to 25 percent of normal needs) Active recovery or low-intensity recovery
Day 6 Typical (100 percent of normal energy needs) Longer duration or higher intensity
Day 7 Typical (100 percent of normal energy needs) Longer duration or higher intensity

If you followed an eating window schedule like the 16:8 plan, however, it may look like this:

Time Intake of energy Type of activity
8 p.m. until 12 p.m. the following day (16 hours) None Only low-intensity (e.g. gentle yoga, walking)
12 p.m.: 1st meal Normal Only low-intensity
4 p.m.: Meal No. 2 Normal Only low-intensity
6–7 p.m.: Workout   Intensity increases (e.g. weightlifting, metabolic conditioning)
7:30 p.m.: 3rd meal Normal Recovery
8 p.m.: Last dinner; no more eating until 12 p.m. the next day None Only low-intensity

Pointer #4: Experiment to find out what works best for you.

We talked about experimentation in a few of the earlier chapters, and we’ll talk about it again here.

You may find that you’re one of the few people who can push themselves to their limits with both exercise and IF.

Alternatively, as Dr. Berardi did, you can determine that the best technique for you is:

  • Fasting less frequently and/or for a shorter period of time
  • Following your workout, eat your largest meals.
  • Increasing your energy intake in order to meet your exercise requirements

Alternatively, you can decide on a completely other approach.

The idea is that figuring out what’s best for you usually takes some trial and error. And that the best and only way to discover your own unique personal recipe is through trial and error. Continue reading to learn more about how to try fasting. Everything you need to know is explained in the following chapter.


To see the information sources mentioned in this article, go here.

If you ever heard about the term “intermittent fasting”, it might be because you’ve been doing it for a long time, but it’s not something you noticed!  If so, you’re probably wondering what the hell it means, and you’re totally right!  You see, intermittent fasting is a way to get rid of hunger by eating fewer calories.  And as you probably already know, that’s the best way to lose weight.  You don’t have to do it all the time, but once a week you should be able to lose up to 1 pound of fat.. Read more about post workout fasting and let us know what you think.

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Frequently Asked Questions

Can I workout while intermittent fasting?

Yes, intermittent fasting is a great way to workout. Its also a good idea to do some cardio while youre doing it.

Is fasting while working out bad?

Yes, it can be bad for your health.

Can you build muscle while fasting?

Yes, you can build muscle while fasting.

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