HIIT And Intermittent Fasting: What are Pros & Cons

High-intensity interval training (HIIT) and Intermittent fasting both are crucial for a healthy lifestyle for many reasons. Many studies have proven the benefits of intermittent fasting and HIIT. Especially both are quite important from a weight loss perspective.

Well, in this article, I’m going to cover some important points about HIIT and intermittent fasting that will give you an idea of why you should or shouldn’t adopt both of them in your daily routine.


  • What is High-intensity interval training (HIIT)?
  • Benefits of HIIT
  • What is Intermittent Fasting?
  • Benefits of Intermittent Fasting
  • Pros And Cons Of Doing HIIT And Intermittent Fasting Together
  • When you should do HIIT; After, during or before Intermittent fasting?
  • How can you safely exercise while fasting?
  • Who should avoid HIIT and time-restricted fasting?

Intermittent Fasting and HIIT
Credit: Thoroughly Reviewed

What is High-intensity interval training (HIIT)?

HIIT or High-Intensity Interval Training is a workout program which includes intense burst activity for a fixed amount of time followed by a recovery period or less intense activity.

In other words, a workout program which is to be performed at high-intensity with a short time interval between exercises.

Let’s take an example of 10 minutes running HIIT. Below is the breakdown of this 10-minute HIIT running. (Warm-up before the start, you can do squats, jumping jacks or high knees)

  • 2-Minute moderate run at 75 per cent of your maximum heart rate.
  • 30 Seconds Slow walk.
  • 2-Minute run at 80 per cent of your maximum heart rate.
  • 1-minute Slow walk
  • 3-Minute run at 85 per cent of your maximum heart rate.
  • 1-minute Slow walk
  • 30 seconds run at 90 per cent of your maximum heart rate.

This is just an example of HIIT. Everyone has a different fitness goal so their selection of exercises is. But the pattern (intense burst activity followed by a low-intensity activity or recover period) is similar for all, irrespective of exercises you chose.

HIIT exercises are usually to be performed at 80 to 95 per cent of maximum heart. However, It depends on person to person.

The average duration of a High-intense activity- 30 Seconds.

And the average duration of recovery period after 30 seconds intense burst activity- 15 seconds.

Benefits of HIIT

  • HIIT is a calorie-burning workout which burns more calories than other forms of workout program.
  • You’ll have the advantage of “after-burn effect“. It means your body uses fats and burn calories even after the workout (usually till 24 to 48 hours).
  • If you maintain your calorie deficit, It will help you lose weight faster than normal.
  • HIIT exercises enhance endurance and improve overall fitness.
  • High-intensity exercises may not be effective for muscle gain but it improves bone density and strengthen skeletal muscles.
  • According to a study, HIIT improves VO2peak (it is the highest rate at which your body uses oxygen during the exercise).
  • HIIT exercises are quite beneficial for heart and lung health.
  • Intense burst activities also enhance respiratory function, improve blood pressure and maintain insulin level.
  • HIIT is also beneficial for mental health. Doing HIIT on a regular basis keeps your mind active and cultivate new ideas.

What is Intermittent Fasting?

Intermittent fasting (IF) is the time-restricted fasting pattern. Time-restricted means you have to maintain your fasting and eating time for the selected period of time.

Let’s understand with an example, suppose you have decided to follow 14:10 fasting pattern. It means you have to keep fast for 14 hours and you can eat in the rest 10 hours (but not whatever you want).

You can complete this fasting scheduled according to your lifestyle. Suppose if you’re 9 to 5 employee then you can have your last meal at 6 and your next will be at 8 in the morning.

Pattern of the intermittent fasting depends on one’s lifestyle.

To get a better result from Intermittent fasting maintain your calorie deficit. Eat low calories food and a good amount of protein to accomplish your fitness goal faster.

Benefits of Intermittent Fasting

  • According to an article published in the National Institute of Ageing, intermittent fasting improves certain health conditions such as cardiovascular disease, obesity, diabetes, cancers and neurological disorders.
  • Intermittent fasting often results in decreased calorie consumption. And because of this you body uses stored fat for energy that ultimately helps you lose weight.
  • Time-restricted fasting also beneficial for them who don’t have the time to exercise or resources to count calories. If you maintain your calorie intake fasting helps you a lot in weight loss management.
  • Another study verified that intermittent fasting lowered total cholesterol by about 11 per cent on average.

Pros and Cons of Doing HIIT and Intermittent Fasting Together

Here are benefits of doing HIIT during the fast.

  • A study demonstrated that doing both HIIT and Intermittent fasting together may help to improve the lipid profile.
  • Many research has shown that combining both Intermittent fasting and HIIT boosts Human growth hormone (HGH) which is important for growth, body composition, cell repair, and metabolism.
  • Another study has demonstrated that Intermittent fasting, with or without HIIT, can be an effective way to prevent weight gain in spite of consuming sugar and high-fat diet. Both HIIT and IF use fats during any activity and exercise which results in decreased calorie consumption
  • Doing HIIT along with intermittent fasting also reduce the level of insulin and seems to be the important time-efficient strategy for the treatment of type 2 diabetes.
  • Combing both intermittent fasting and HIIT is a time-efficient approach for weight loss.

Disadvantages of Combining HIIT And Intermittent Fasting Together

Doing HIIT And intermittent fasting together isn’t always works best for everyone. Here we take a look at some drawbacks of combing HIIT and IF.

  • Performing high-intensity exercising in the fasted mood, makes you feel uncomfortable. For example, you may feel headache, dizziness, fatigue, low blood pressure and abnormal heart rate.
  • Sometimes, fasting can reverse the effect of weight loss. Because after a period of fasting people tend to eat starchier foods which contain high calories. Usually, carbohydrates are the main source which fuels the energy in the body. Extreme hunger also causes you to consume more calories than you eat without fasting. And as a result, fasting can reverse the effects of a weight loss plan.
  • Some reaserch have also shown that fasting in the long term may slow down your metabolism.
  • When you’re in the fasting state, you’ll have less energy. And because of this you wan’t be able to work out as hard as you perform in the normal state.

When you should do HIIT exercises: After, during or before Intermittent fasting?

This question is also quite important for you. Performing high-intensity exercises before, during, or after the fasting depends on person to person.

Exercising before fasting is fitting for someone who performs well during the exercises. Working out before fast will also be ideal for them, who want to workout and fast separately and put more focus on one at a time.

While exercises during the fast will be perfect for them who perform well during the exercise on an empty stomach. It will be useful for them who have enough energy to perform high-intensity exercises without getting faint.

And, working out after the fasting period is ideal for those who haven’t got the opportunity to exercise during or before the fasting mode. It will also fit them who want to capitalize post fasting diets.

I can’t suggest doing exercises before, during or after the fast. Because I don’t know how your body responds. So, it is up to you and your body.

What I can suggest are

  • Always listen to your body, just don’t pressurize it.
  • Try all three of them for a certain period of time, then do what suits you the best.
  • Keep yourself hydrated whenever you do exercises.

proper ways to exercise while fasting

If your goal is weight loss or muscle gain, it is important to understand how you exercise more than what you exercise. Because improper routine or exercises not only affect your fitness goal but also cause you other health problems.

Here are some important points you should keep in mind when your plan is combining HIIT and intermittent fasting together.

  • Eat some calories and protein close to your HIIT workout. Because it helps you perform well during the exercises.
  • Whether you’re in the fasting state or in the normal state, keep yourself hydrated during the exercise.
  • Avoid strength training while you’re fasting because strength training requires more carbohydrates.

Who should avoid HIIT and time-restricted fasting?

Most of the people have different goals so their ways are. That is why if plan A works for you then it doesn’t mean it will work for others. Or if others easily managing HIIT and IF it doesn’t mean that you’ll also manage it.

Here is the list of people who should avoid both HIIT and fasting.

  • People who want to increase their weight and gain muscles.
  • Pregnant women.
  • Malnourished or undernourished person.
  • People with an eating disorder or suffering from Prader-Willi.
  • People who have other health problems.

Final Words

Both High-intensity interval training (HIIT) and Intermittent fasting are scientifically proven ways to maintain a healthy lifestyle. But sometimes they also affect reversely, that is why it is important to manage both of them in a proper way. If you have or you feel any kind of health issue before, during or the fast or workout, stop doing it and consult with the doctor before restarting any of them.

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