All you need to know on Intermittent Fasting and Exercise

Intermittent fasting is certainly not new. People have been doing shirt fasts for many years for a variety of purposes. Now it seems that some people are combining intermittent fast and exercise to achieve some intense fitness goals.

Intermittent fasting and exercise can be done together safely. There is both scientific and anecdotal evidence to show that intermittent fasting and exercise will lead to substantial weight loss and other forms of fitness. 

One of the big questions is whether or not intermittent fasting and exercise are healthy when done at the same time. It may sound counter-intuitive to fast while trying to maintain an exercise program. Your body needs nutrients after all.

But it is possible to do intermittent fasting and exercise at the same time. This requires some planning, but intermittent fasting and exercise can work together. What you need is an understanding of the benefits of intermittent fasting and exercise and weigh these against the potential complications. 

What are the benefits of fasting? How do we combine fasting with exercise? And how do we do intermittent fasting and exercise to achieve the best results? This guide will provide the information you need to get started with intermittent fasting and exercise. 

What is intermittent fasting?

Intermittent fasting, or IF as it is sometimes called, is simply a pattern of eating that cycles between periods of fasting or not eating and periods in which you do eat. This is essentially a diet plan that does not regulate what you eat but when you eat. 

Some of the more common patterns of intermittent fasting involve 16 to 24-hour fasts about two times a week. 

The idea behind intermittent fasting is based on an evolutionary model. The idea is that before human populations had easy and instant access to food at grocery stores and with refrigeration, people would necessarily go without food for short periods. As a result, the theory goes, the human body is biologically prepared to go for short periods without eating. 

This presupposes that the human body is naturally prepared to go without eating from time to time and that eating 3 meals a day (or more) is not natural. We will be more in tune with the natural mechanisms of our bodies if we go without eating for short periods. 

Intermittent fasting health benefits

The benefits of intermittent fasting run from the body to the brain. Numerous scientific studies have supported the practice of intermittent fasting. The benefits of intermittent fasting include:

Weight loss

One of the most obvious benefits of intermittent fasting is weight loss. It can specifically reduce belly fat. 

Insulin resistance

Research has shown that intermittent fasting can reduce insulin resistance. This is a crucial factor in reducing the risk of type 2 diabetes. 

Reduces inflammation

Intermittent fasting has been clinically shown to reduce the key markers of inflammation. Chronic inflammation is one of the main causes of many serious illnesses and diseases. 

Heart health

Intermittent fasting can reduce the so-called bad cholesterol, or LDL, and triglycerides. These are the primary drivers of heart disease. 

Reduce the risk of cancer

There is abundant laboratory evidence to show that intermittent fasting can prevent multiple forms of cancer. 

Brain health

Intermittent fasting stimulates the production of a hormone called BDNF. This is associated with growing nerve cells. Researchers now believe that intermittent fasting can prevent the onset of neurodegenerative disorders like Alzheimer’s disease. 


There is some clinical evidence to show that intermittent fasting can extend the life span. 

Does intermittent fasting work without exercise?

Intermittent fasting came about independent of exercise. Much of the early anecdotal evidence and quite a lot of the clinical evidence on intermittent fasting relates primarily to IF without exercise. 

People began doing intermittent fasts to restrict calorie intake and to lose weight. While this had obvious positive results, one of the important things researchers discovered was that intermittent fasting has a positive effect on the chemistry of metabolism. 

Intermittent fasting can alter hormones that control metabolic rate. This leads to increased weight loss on top of the weight loss from restricted calories. It also has the benefit of long-term weight loss because the changes in metabolism remain in place even after the fasting is complete. 

This last benefit has the collateral benefit of helping to control insulin and blood sugar levels. Intermittent fasting independent of exercise can help control things like type 2 diabetes. 

The simple answer is yes, intermittent fasting does work even without exercise. 

When is the best time to exercise when intermittent fasting?

Timing is everything if you are going to combine exercise with intermittent fasting.  The key is to make certain you have enough macronutrients present in your system before you exercise. 

If you are doing a simple 30 minutes of cardio, it is fine to go ahead and exercise after the fasting part of your intermittent fast. But if you are doing much more than this you will need enough glycogens available to support the exertion of a workout. 

The best time to exercise during intermittent fasting can have answers. One way of going about this is to eat a small snack just before exercise. Roughly 20 minutes before you work out, eat enough carbs to build up your glycogen stores for the energy needed for exercise. 

The other way to approach this is to time your meals for an hour to two hours before exercising and go into your fasting period after your workout. This is more important for things like weight training where you need plenty of protein in your system to achieve the gains you are after. You cannot build muscle without the macronutrients that make muscle. 

How to safely exercise while intermittent fasting

The best way to safely exercise while intermittent fasting is to follow these simple tips.

Plan and time properly

The key here is to understand what will work best for your workout. Should you exercise before, during, or after your refueling period? 

A common method is to stick with what is called the 16:8 intermittent fasting protocol. This means you eat food during an 8-hour refueling window and fast for 16 hours for the rest of the day. 

Depending on your exercise program, you will need to decide which will work best, before, during, or after refueling. As we noted above, simple and short cardio workouts are fine after fasting. For more intense exercise, you may need to work out right after eating. 

There is more to this than making sure you have enough macronutrients for the workout. Some exercise programs benefit from refueling immediately after exercising. Muscle protein synthesis and muscle recovery tend to benefit from post-exercise fuel. 

Choose macronutrients based on your exercise program

It is important to think about what kinds of exercise you are doing and choose foods that accommodate this. This means planning some types of macronutrients the day before exercise and others for after exercise.

For things like HIIT, you need to make sure your body has plenty of available glycogen stores for this type of intense exertion. For weight and strength training, you will need to plan protein-rich meals for after exercising. 

Eat the right things after exercising

If you are doing intermittent fasting and exercise together primarily for weight loss, you do not want to consume a lot of carbs after your exercise program. The idea is to save carbs for available energy before exercise.

As noted above, eating plenty of carbs and protein after working out is important to weight training. These macronutrients provide the building blocks of muscle proteins.  

Other things to consider:

The success of any fitness or weight loss program depends on your ability to sustain it. Maintaining a program of intermittent fasting and exercise requires you to be safe about how you proceed. These tips will help you sustain your program over the long-haul.

Eat meals close to a moderate to high-intensity workout.

For these kinds of exercises, you need to have available glycogen stores to sustain your energy levels. Timing meals closer to your workout will be essential. 

Stay hydrated

This is always the case, but it becomes especially important during intermittent fasting and exercise. Since you are not taking in food and nutrients at more common intervals, you will need to pay particular attention to staying hydrated. 


The fasting periods will use up available electrolytes simply as your body works to sustain normal functions. This will cause you to use up electrolytes quickly when you exercise. You can maintain electrolytes with things like coconut water which naturally contains high levels of electrolytes. Avoid sugary sports drinks. 

Keep the intensity and duration low

If you go too hard while you are combining intermittent fasting and exercise you can get dizzy and/or lightheaded. Take breaks and listen to your body. 

Adjust the type of fast

There are different ways to intermittent fasting. Experiment with the one that works best for your exercise programs. The 16:8 fast is just one way of doing this. There are also 24-hour fasting periods. For this type of intermittent fast, you may want to consider low-intensity exercises like walking, restorative yoga, or gentle pilates.  

Pay attention to your body

If you are struggling to get through a normal exercise routine, you may need to re-think the way you are doing your intermittent fast and exercise. 

Pros and cons of exercising while on a fast

Like anything else, there are advantages and disadvantages to intermittent fasting and exercise. Some may find that sustaining both practices is simply too much for them. Others will find results from intermittent fasting and exercise that they could never achieve doing one or the other by itself.  

The pros of intermittent fasting and exercise include:

  • Great way to lose weight and keep it off.
  • A host of additional health benefits like heart and brain health. 
  • Retrain the metabolism for healthier weight and BMI. 
  • Helps to reduce blood sugar and prevent type 2 diabetes. 

The cons of intermittent fasting and exercise include:

Poor exercise performance. Some people will find that their overall exercise performance suffers from fasting.  

  • Difficulty building muscle: For some people, intermittent fasting can make it difficult to build muscle even if they carefully time their macronutrient intake.
  • Lightheadedness: Some people have experienced drops in blood pressure after fasting and exercising.
  • Low blood sugar levels: The combination of intermittent fasting and exercise may lead to dangerously low blood sugar levels. If blood sugar levels get too low, you may become susceptible to fainting. 

To balance the pros and cons of intermittent fasting and exercise you need to think seriously about the kind of exercise you do and exactly what your fitness goals are. For people who need or want to lose weight, intermittent fasting with low-intensity exercise can be miraculous. This combination is known to help you shed pounds, belly fat, and keep it off. 

For people who are primarily interested in high-intensity training and workouts, the combination of intermittent fasting and exercise may not be the best way to go. Ultimately, the only way to approach this is with proper planning and by listening to your body. 


Exercise, fitness, and dieting trends are coming up all the time. We need to be careful as we approach these things. These trends can sometimes be ineffective, and sometimes they turn out to be dangerous. Intermittent fasting and exercise are one of those trends that has some real science behind it. 

Intermittent fasting and exercise are based on the idea that humans had to evolve to be able to go without eating for short periods. Before there were grocery stores everywhere, and before there were large-scale farming techniques, humans had to find food on their own. When food was scarce, they went without. 

The theory is that because of these evolutionary features, our bodies are naturally tuned to going for short spaces of time without eating and we naturally benefit from fasting. As it turns out, there are some real health benefits to intermittent fasting. Planned, intermittent fasting can benefit the body and the mind. 

If we exercise while working with an intermittent fasting program, we can see further benefits. The most prominent benefit of intermittent fasting and exercise is weight loss. By fasting for short, planned times, and exercising, we can lose weight, trim the belly fat, and even reset our metabolism so that it is harder to gain the weight back. 

There are disadvantages to intermittent fasting and exercise. People who do intense forms of exercise like serious weight and strength training may not benefit from intermittent fasting and exercise. The fasting periods can make it difficult to sustain the macronutrients necessary to support intense training and exercise. But the good news is that intermittent fasting and exercise are safe and can be extremely beneficial. 


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