The Pros and Cons of Fasting

by | Oct 3, 2018 | Nutrition, Nutrition Facts | 0 comments

Inside Scoop: The pros and cons of fasting and what you need to know before attempting a fast.

This post was submitted by Penny Brown, a Physical Therapist with a degree from Columbia University.

Limiting calories or food is nothing new to us, it’s existed as a spiritual practice for many religions and cultures, and it’s been around for thousands of years.

Today, fasting is gaining popularity as another element of a healthy lifestyle. Many people are now using fasting for weight loss, to prevent aging, to overcome addictions, to boost immunity and to detox. But is this hype really backed by evidence and what are the known pros and cons of fasting?

What is Fasting?

Traditional fasting can be seen as a period of time when very little or no food is eaten. People may choose to do this due to spiritual, religious or health reasons as well as when preparing for medical tests. A typical fast can be anywhere from 24 to 72 hours.

What Are The Different Types Of Fasting?


People choose to fast for religious reasons as they often see it as a way to ‘cleanse the soul’. Periods of fasting often accompany times of prayer. For example, people of Islamic faith fast during the day for the month of Ramadan and some Christians choose to fast during Lent.


A dry fast is abstinence from all food or drink while a water fast allows only water as a liquid during the fasting period. This involves consuming water only for anywhere between 24 to 72 hours. Some fasting diets also allow for black coffee and tea.

Even though water fasting may have some benefits, it can also come with some side effects, such as raised blood pressure, headaches, nausea, fatigue and even low sodium levels and dehydration.


Intermittent fasting (IF) involves a way of eating which includes periods of fasting and non-fasting. This is often more manageable for new-time fasters and can even offer some of the same health benefits as fasting. There are several types of intermittent fasting including:

  • The 5:2 method which involves eating normally for five days of the week and eating 600 calories at most per day twice a week.
  • With the 6:1 method, you don’t have to change your diet for 6 days of the week and you fast completely for 24 hours one day per week.
  • Alternate day fasting where you eat normally one day and fast for the next 24 hours and repeat that for the whole week.
  • The 16:8 method involves eating for 8 hours each day and fasting for 16 hours within a 24-hour time frame. This is one of the most popular IF methods.


What Are The Health Benefits?

Fasting naturally can help you to reduce food and calorie intake, as you won’t be eating as much or as often as usual. But this is not where the true benefits of fasting lie. According to research, fasting may the risk of diseases such as type 2 diabetes, affect our metabolism and biochemistry and even reduce inflammatory markers and autoimmunity in conditions like multiple sclerosis.

According to the Health Sciences Academy intermittent fasting may also be good for your gut bacteria. Some might believe that if you skip a few meals your gut bacteria will starve, but apparently this is not the case. A study on mice showed that fasting actually increases bacterial diversity. Fasting for 24 hours or more, not only helped feed the good bugs but also lowered inflammation. You can read more about the study here.

One study also found that intermittent fasting may reduce symptoms of depression as a significant reduction in low mood, confusion, tension and anger was observed.

It’s important to be aware of both the pros and cons of fasting to make an informed decision, so next we’ll be focusing on some unpleasant and sometimes dangerous side effects.

Are There Any Health Risks?

While fasting may offer some significant benefits, you can also expect a few side effects such as headaches, lack of energy, patterns of disordered eating and some other more serious health issues.

Fasting should, therefore, be avoided by people who need a regular supply of nutrients such as those who are malnourished, breastfeeding or pregnant women and growing children. Some women have even reported negative side effects such as binge eating, changes in metabolism and missed periods when fasting.

Fasting has also even been associated with reductions in exercise ability, muscle mass and athletic performance.

Serious risks are generally associated with prolonged fasting. If you want to stay safe while fasting, make sure to consider the following.



Consult A Doctor Before You Start

Make sure to speak to your doctor to find out how to fast without harming your health, especially if have a health condition. Your healthcare provider will help you to create a customized plan for your unique body.

Don’t attempt to fast on your own and especially if you are pregnant, breastfeeding, malnourished, or suffer from a serious health condition such as diabetes. Fasting is not recommended for anyone with or that is recovering from an eating disorder, or long-term dieting and weight loss.


Try Different Tactics

If you’re fasting to lose weight, consider using a modified approach – as rapid weight loss won’t be beneficial in the long-run. It is important to lose weight slowly in a healthy and balanced way as this will allow you to maintain enough muscle to keep your metabolism stimulated. Instead of fasting rather try to gradually make small changes with your diet, lifestyle and habits.

You can start to cut back on soda, highly processed foods, packaged foods and sugar, and adding more fruits and vegetables to your diet. Try to focus on what you can have instead of what you cannot have so you can start to master natural weight loss.

Take this 5 Ingredient Challenge that will help you create healthy habits in as little as 5 days. Filled with delicious recipes made with 5 ingredients or less and plenty of handouts and healthy tips delivered straight to your inbox daily. Join the challenge below.

Change Your Exercise Routine

Now that you know the pros and cons of fasting, if you do attempt any of the fasting methods you’ll have to consider what changes should be made around your daily activities.

This would greatly depend on the type of fasting you are doing, but it might be wise to put off high-intensity workouts until the fasting period is over. Light to moderate activities like basic yoga, meditation or walking would be a good bet, but forego your HIIT or spinning class.


Drink A Lot Of Water

The amount of water you should drink daily depends greatly on your environment, body size and activity level. You might realize that you need less water when fasting – this might be due to decreased activity levels. It’s still important that you continue drinking enough water to keep your body hydrated.


Plan Your Meals

When you’re fasting, your eating window is limited which means that you may not be able to get all the essential nutrients your body needs daily. So, the meal choices during the eating periods should be nutritious and well balanced. Try to have well-rounded meals with lean protein, healthy carbs and fats and plenty of fruits and vegetables.

I hope that the pros and cons of fasting have given you the information to be better equipped to make the right food and nutrition choices for your body. If you need more info on what a healthy lifestyle would look like to you (whether it includes fasting or not) check out

Penny Brown

Penny Brown, a Physical Therapist with a degree from Columbia University, passionately believes in the importance of optimal health, at any age. You can find her regularly competing in triathalons along with her partner, Breanna, and their 2 children, Roxie and Joe. When she's not working or training for her next race, she enjoys swimming, hiking and reading nonfiction writing.

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