19.SEP.2019 4 MIN READ | 4 MIN READ

Intermittent fasting may be a popular wellness trend but does it really work? More importantly, is intermittent fasting healthy?

Last updated on 5 January 2022

Intermittent fasting has been touted as the easiest way to lose weight and improve health. It is said to fortify the body against diseases and improve long-term health by repairing the body at the cellular level. Potential benefits include better diabetes control and prevention, cancer prevention, improved cholesterol profile, and boosted brain power. Some people even believe intermittent fasting can result in a longer lifespan.

Some of our favourite celebrities reportedly swear by intermittent fasting. Famous faces who adopt this approach include:

  • Hugh Jackman – The Wolverine star only eats during an 8-hour window each day
  • Nicole Kidman – The Australian actress only fasts for up to 16 hours a day and tucks into lean proteins and vegetables for the rest of the time
  • Chris Hemsworth – Best known for his role as Thor, the Australian actor is known to fast for up to 15 hours a day as a means to maintain his physique

But what is intermittent fasting and how should you do it? While research on its long-term effects is limited, here is what we know about its benefits and risks.

What is intermittent fasting?

What is intermittent fasting?
Intermittent fasting is not about denying yourself your favourite food. Instead, it’s all about when you eat them. This means you follow set periods of eating and fasting throughout the day. Specifically, how long you fast for depends on your compliance and what best fits into your eating patterns.

How does intermittent fasting work?

Many people eat regular meals with snacks in between, providing the body with plenty of energy without having to burn any stored fat. By going without food for a prolonged period, intermittent fasting encourages our body to tap into our fat storage more quickly and efficiently for energy. This is known as metabolic switching.

How to practice intermittent fasting safely

There are several intermittent fasting methods and while all of them can be effective, our bodies may react differently to certain eating and fasting periods. Therefore, it is important to figure out which schedule works best for you. The following are some popular intermittent fasting methods:

16:8 method

The 16:8 method requires you to fast for 16 hours overnight, leaving an 8-hour window during the day to eat food normally. Some choose to skip breakfast and eat lunch and dinner; others choose to eat breakfast and lunch and skip dinner.

5:2 method

The 5:2 method involves fasting for 24 hours twice a week and eating normally for the rest of it the week. During the fasting period, they restrict their intake to only 500 – 600 calories a day. With this method, it is also important to drink adequate fluids such as water, zero-calories drinks to help stay hydrated and keep energy levels up.

Eat stop eat method or 'The 24-hour fast'

Eat stop eat means completely abstaining from food for one or two non-consecutive days in a week, and eating normally during the other days. It’s important to remain hydrated and choose healthy food options.

Alternate day fasting

As its name suggests, this method involves fasting every other day. On fasting days, water and unsweetened beverages are permitted. Some people may prefer to modify this method by allowing 500 calories on fasting days.

It’s important to determine why you want to try intermittent fasting, and what you hope to achieve. Any type of fasting could be dangerous if you’re on certain medicines or have certain types of medical conditions. Consult your doctor to figure out which method works best for you.

Does intermittent fasting work?

While there is not enough evidence to prove the long-term benefits of intermittent fasting, it can help cultivate healthier eating habits. Intermittent fasting could help you maintain a healthier weight as people tend to consume lesser calories during a restricted window for eating.

Benefits of intermittent fasting

Some studies have shown that calorie restriction and different forms of fasting can have major physiological effects. During fasting periods, your body may produce more fat-burning hormones that help boost your metabolism and allow you to drop pounds without losing muscle tone. There is also evidence that metabolic switching could have additional benefits. These include:

Cognitive effects

Intermittent fasting has been shown to boost memory.

Heart health

Some studies have found that intermittent fasting improves blood pressure and resting heart rates.

Metabolic effects

In several studies, obese individuals were able to lose weight through intermittent fasting.

Maintaining a healthy diet

While these benefits are encouraging, it’s crucial to maintain a well-balanced, healthy diet during your set eating periods too. Consuming unhealthy junk food when you’re not fasting could hinder weight loss in the long term.

For more effective results, make sure your body is still getting all the nutrients it needs and continue exercising regularly for at least 30 minutes a day, 5 times a week.

Is intermittent fasting safe?

It is important to know your limits and not overdo any diet or fasting plans. Starving yourself, over exercising, not drinking enough water, or eating too little during your break-fast period can be detrimental to your health as you deprive your body of the necessary nutrients and resting periods needed to function properly.

Here are some tips on how to practice intermittent fasting safely:

  • Keep fasting periods short

    Fasts that last over 24 hours could leave you feeling irritable, dehydrated or tired
  • Stay hydrated

    Don’t forget to drink water even while you’re fasting to avoid developing a headache, dry throat or getting dehydrated
  • Eat an adequate amount of protein

    This will help to minimise muscle loss and help you manage your hunger more effectively
  • Don’t over exercise

    Some people find it easier to exercise during eating periods and only do mild exercise during fasting periods
  • Don’t overeat

    Breaking your fast with a big meal may make you feel bloated, uncomfortable or tired. It may also eventually make you put on weight if you continue to overeat. If you find yourself feeling too hungry or if you often overeat during your break-fast periods, consider shortening your intermittent fasting time.
  • Stop fasting if you feel unwell

    Seek medical help if you feel extremely weak or experience unexplained discomfort

Risks of intermittent fasting?

Intermittent fasting risk
While intermittent fasting can have its benefits, it’s important to remember that it’s not the right choice for everyone. You don’t need to fast to be healthy and happy.

Some risks and side effects that may occur with intermittent fasting include:

  • hunger pangs and cravings
  • headache or lightheadedness
  • mood swings (irritability, crankiness)
  • fatigue/low energy
  • dehydration
  • constipation
  • sleeplessness
  • bad breath

Who should avoid intermittent fasting?

Intermittent fasting may not be right for everyone, depending on your age and health condition. Individuals who should avoid intermittent fasting include:

Women with abnormal menstrual cycles and those trying to conceive

Intermittent fasting may interfere with some women’s menstrual cycles, so if you have abnormal menstrual patterns or if you’re trying to conceive, you may wish to hold off trying it for now.

Pregnant women

Intermittent fasting can cause blood sugar levels to dip, causing pregnant women to feel faint or lightheaded. Low blood sugar can also be harmful for the baby as it can result in decreased foetal movement.

Those who have pre-existing medical conditions

It may be dangerous to fast if you have a pre-existing medical condition such as diabetes or low blood pressure. Eating plans and schedules for those with pre-existing medical conditions require extra care and attention, and should be professionally recommended and monitored by your doctor.

Those who have or have had an eating disorder

Individuals with a history of eating disorders may also find it’s not the right choice for them.

Children and teenagers

Intermittent fasting is not recommended for children or teenagers. During these years of rapid growth, it is advisable to help children maintain a healthy weight through planned, nutrient dense meals and snacks to manage hunger while providing sufficient nutrients for growth and development.

If you’re considering trying intermittent fasting, make sure you book an appointment to speak to your doctor or dietitian first. They’ll be able to help you plan a safe eating plan and monitor how well it works for you.

Quote "IWANNABELEAN" for a first 45 minute consultation with a dietitian at $82 (including GST) with a Shenton general practitioner's referral. Call 6933 0231 to make your dietitian's appointment.

 

Article reviewed by Wong Hui Mei, senior dietitian at Gleneagles Hospital

Reference

(4 June 2017). 6 Popular Ways to do Intermittent Fasting. Retrieved 9 July 2019 from https://www.healthline.com/nutrition/6-ways-to-do-intermittent-fasting#section2

(25 July 2018). Intermittent Fasting 101 — The Ultimate Beginner's Guide. Retrieved 9 July 2019 from https://www.healthline.com/nutrition/intermittent-fasting-guide

(2 August 2018). 10 Celebrities Who Swear by Intermittent Fasting. Retrieved 9 July 2019 from https://www.delish.com/food/g22617665/celebrities-intermittent-fasting/

(26 November 2018). Intermittent Fasting. Retrieved 9 July 2019 from https://www.webmd.com/diet/a-z/intermittent-fasting

(2 January 2019). How to Fast Safely: 10 Helpful Tips. Retrieved 9 July 2019 from https://www.healthline.com/nutrition/how-to-fast

Yavangi M, Amirzargar MA, Amirzargar N, Dadashpour M. Does Ramadan fasting has any effects on menstrual cycles?. Iran J Reprod Med. 2013;11(2):145–150. Retrieved 16 July 2019 from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3941357/#.

Lessan, N and Ali, T. Energy Metabolism and Intermittent Fasting: The Ramadan Perspective. Retrieved 16 July 2019 from https://www.ncbi.nlm.nih.gov/pubmed/31137899

(n.d.) Intermittent Fasting: What is it, and how does it work? Retrieved 13 December 2021 from https://www.hopkinsmedicine.org/health/wellness-and-prevention/intermittent-fasting-what-is-it-and-how-does-it-work

(7 January 2020) Eat Stop Eat Review: Does It Work for Weight Loss? Retrieved 13 December 2021 from https://www.healthline.com/nutrition/eat-stop-eat-review

(4 August 2020) Alternate-Day Fasting: A Comprehensive Beginner's Guide. Retrieved 13 December 2021 from https://www.healthline.com/nutrition/alternate-day-fasting-guide

(31 August 2021) 4 reasons intermittent fasting is not safe for pregnant people. Retrieved 13 December 2021 from https://www.cnet.com/health/parenting/reasons-intermittent-fasting-is-not-safe-for-pregnant-people/

(1 October 2018) Intermittent Fasting: Is it Safe for Kids? Retrieved 13 December 2021 from https://health.choc.org/intermittent-fasting/

19.SEP.2019
img
Wong Hui Mei
Senior Dietitian
Gleneagles Hospital

Ms Wong is a dietitian member with the Malaysian Dietitians’ Association.