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Pros and Cons of Intermittent Fasting

All of us have probably heard about intermittent fasting, whether from a friend, social media or celebrity news. Instead of changing what they eat, people simply change the times that they eat, and they lose weight – how easy!

You might be scratching your head and wondering whether this diet is all it’s cracked up to be.

In this article, we’ll consider what intermittent fasting is along with the potential benefits and drawbacks of this trending eating pattern.

What is intermittent fasting?

Intermittent fasting is an eating pattern where a person regularly goes for an extended time (16-48 hours) without consuming energy (calories).(1) Outside of the fasting time, there is an eating window where the person can eat normally. In general, intermittent fasting is about the timing of food rather than types or amounts of food eaten.

There are several intermittent fasting programs, some popular ones are:

  • The 16/8 method – fasting for 16 hours with an eating window of 8 hours per day
  • The 5:2 diet – a very low-calorie diet for 2 days per week (a ‘partial fast’)
  • Alternate day fasting – fasting on every second day


Does intermittent fasting work?

Intermittent fasting has been found to be beneficial for weight loss(2-4), diabetes control(3) and certain cholesterol levels,(5) compared to a non-restricted eating pattern (eating normally).

Interestingly, when these studies compared intermittent fasting to calorie-restricted diets, the weight loss, diabetes control and cholesterol level improvement were very similar!(2, 3, 5, 6) This means that intermittent fasting can help, but it’s not necessarily better than creating an energy deficit through a restricted calorie intake.

It’s important to note that the long-term effects of intermittent fasting are not well studied – most studies are short-term (less than 12 months) and it’s possible that the benefits from intermittent fasting don’t continue after 12-18 months.(3)

The key factor for weight loss is the creation of a consistent and prolonged energy deficit. You might have heard of this as “more energy out than in”. This means that we are expending more energy (through exercise and functioning at rest) than we are consuming (through food and drink). A large body of scientific research supports the use of moderate & consistent energy deficits for long-term weight loss.

Should I do intermittent fasting?

If you are considering doing intermittent fasting, there are some drawbacks of this eating pattern which should be considered:

  • If you have many social commitments, it might be difficult to stick to a fasting regime. Since consistency is important to achieve results, it’s worth asking: is it sustainable for you to commit to intermittent fasting?
  • If you are a parent, your kids observe and learn your eating habits. Since it’s important to be modelling good eating behaviours, fasting may not be the best option in this context.
  • With long-term intermittent fasting, there may be a risk of protein malnutrition and other nutrient deficiencies. To avoid this, it’s essential that your diet is well-planned to ensure that it is nutritionally complete during the times when you are eating. Fasting is not a replacement of building a healthy, balanced diet.
  • The effects of fasting for people with chronic conditions including heart disease, kidney disease and cancer are not well known.(7) Due to the elevated health risks, if you have a chronic condition or have had a stroke, it is recommended to discuss with your doctor or healthcare team before trying intermittent fasting.
  • Some diabetes medications can put you at a greater risk of hypoglycaemia. It can be dangerous to be fasting for extended periods of time while on these medications. If you have diabetes and are considering intermittent fasting, check with your doctor first to provide advice and potentially adjust your medications if suitable.
  • There is a greater risk of dehydration while fasting, so it’s important to drink plenty of water. This includes drinking water to replace the fluids that we would usually get from food (especially foods like berries, melons, cucumbers, yoghurt). You may also need to replace electrolytes to avoid dehydration.


Weigh up the pros and cons

If you’re considering intermittent fasting, weigh up the pros and cons of this eating pattern. Consider what will be beneficial and practical in your life and household. Intermittent fasting isn’t for everyone and what works for someone else may not work for you.

While there are some promising results with intermittent fasting, much of the evidence is short-term. We have also seen that similar results can be achieved with a calorie-restricted diet, individualised to the person’s life, instead of intermittent fasting.

At the end of the day, sustainable healthy eating habits are the key ingredient for long-term health and achieving weight management goals.


There’s no one-size-fits-all approach when it comes to healthy eating! If you would like help finding the healthy eating habits that work well for you, our lovely team of dietitians can help to turn nutrition principles into practical and achievable habits. Get in contact with our team at The Healthy Eating Clinic or call us on 02 6174 4663.

At The Healthy Eating Clinic, we want to equip you with habit-based nutrition advice so that you can eat well for the rest of your life! Make an appointment today






  1. Mattson MP, Longo VD, Harvie M. Impact of intermittent fasting on health and disease processes. Ageing Res Rev. 2017;39:46-58. doi:10.1016/j.arr.2016.10.005
  1. Allaf M, Elghazaly H, Mohamed OG, et al. Intermittent fasting for the prevention of cardiovascular disease. Cochrane Database Syst Rev. 2021;1(1):CD013496. Published 2021 Jan 29. doi:10.1002/14651858.CD013496.pub2
  1. Vitale R, Kim Y. The Effects of Intermittent Fasting on Glycemic Control and Body Composition in Adults with Obesity and Type 2 Diabetes: A Systematic Review. Metab Syndr Relat Disord. 2020;18(10):450-461. doi:10.1089/met.2020.0048
  1. Borgundvaag E, Mak J, Kramer CK. Metabolic Impact of Intermittent Fasting in Patients With Type 2 Diabetes Mellitus: A Systematic Review and Meta-analysis of Interventional Studies. J Clin Endocrinol Metab. 2021;106(3):902-911. doi:10.1210/clinem/dgaa926
  1. Meng H, Zhu L, Kord-Varkaneh H, O Santos H, Tinsley GM, Fu P. Effects of intermittent fasting and energy-restricted diets on lipid profile: A systematic review and meta-analysis. Nutrition. 2020;77:110801. doi:10.1016/j.nut.2020.110801
  1. Welton S, Minty R, O’Driscoll T, et al. Intermittent fasting and weight loss: Systematic review. Can Fam Physician. 2020;66(2):117-125.
  1. Grajower MM, Horne BD. Clinical Management of Intermittent Fasting in Patients with Diabetes Mellitus. Nutrients. 2019;11(4):873. Published 2019 Apr 18. doi:10.3390/nu11040873