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Hot (or not) diets – the 5:2 – by APD Katrina Mills

Dietetics, The Health Industry

Paleo, raw food, 5:2, Mediterranean; the endless choice of diets is even more overwhelming than the breakfast cereal aisle at the supermarket! I am constantly getting asked what do you think about X diet? The claims of all these fad diets are splashed across magazines, TV, radio, Facebook, so in an effort to try and clear up all the misinformation let’s investigate these diets including their positives, negatives and the science (or lack thereof) behind them.

One of the most popular diets around at the moment is the 5:2. Also known as the ‘fast’ diet it became popular at the end of 2012 after a documentary by BBC journalist Michael Mosley. It is a form of intermittent fasting where followers fast for two non-consecutive days per week and then eat a ‘normal’ diet, without any restriction for the other five days.

•   2 x Fasting Days:

  • Women limit their total intake to 2100 kilojoules (500 Calories)
  • Men limit their intake to 2500 kilojoules (600 Calories)
  • These numbers equate to about ¼ of the energy recommended for adults in a health weight range.

•   5 x Feasting Days:

  • On the feasting days, there is no restriction so you can eat whatever you want.


  • Foods eaten on the fasting days are recommended to have very little fat, carbohydrates and alcohol is strictly forbidden.
  • Breakfast: 2 boiled eggs and an apple for breakfast
  • Lunch: Half a bowl of low salt, microwave soup for lunch
  • Dinner: 10 spears of asparagus and 1 capsicum.
  • No snacks. No drinks apart from water and black tea or coffee.


  • Eat whatever you like, until you are full*

On feasting days followers are told to eat until they are full. Writers of the diet are covering themselves here because many of us do not stop eating when we are full. Unless accompanied by training into how to overcome overeating, you may very well over indulge on your feasting days, consume more energy your body needs over the course of a week and therefore struggle to see the benefits of the diet!

The 5:2 diet seems to be becoming more popular because it doesn’t just claim to help weight loss, supporters also claim it reduces the risk of Alzheimer’s disease and helps you live a longer life. There are also recent reports to suggest it could help prevent Type 2 diabetes as well.

Longer life expectancy: Firstly, most of the claims that intermittent fasting leads to a longer life have only been shown in monkeys! There have not yet been any long standing studies testing the same theory in humans. So, we still don’t know if it causes you to live longer.

Weight Loss: An increased amount of human studies have recently shown this diet is effective for short-term weight loss (<6 months). The largest study conducted in this area was done in the UK in 2011. It compared two groups of overweight or obese young women who followed an intermittent fasting diet, like 5:2 and another who ate a diet that was the same reduced calorie diet everyday for six months. It showed that both diets were as effective as each other at reducing weight as well as other markers of health. What was interesting from this study was that only 58% of women on the 5:2 or intermittent fast said they would continue with the diet, compared to 85% of women on the daily reduced calorie diet. Even though this study was run for six months, it is still only considered short term.

Alzheimer’s: There was an article published in the London Telegraph that claimed diets like 5:2 could prevent cognitive decline. The authors said that due to disruption of our body’s natural body clock, or circadian rhythms, that we have begun eating more, making us more likely to become obese and develop diseases. They also suggest that intermittent periods of food restriction can improve health and counteract the disease process like the development of cancer.

Cholesterol & other claims: Personal stories also show that the diet reduces cholesterol, improves your blood glucose levels and helps reduce IGF-1 levels (a hormone which has been associated with cancer risk). Firstly, weight loss in general will reduce all the same markers. So they actually claim that the reduction was primarily due to the pattern of intermittent fasting!

Glycogen stores in the body are emptied which helps with insulin sensitivity. (The more sensitive your body is to the hormone insulin, the more likely your body is to store glycogen in the muscles rather than laying down fat deposits). Everything to do with being hungry (on fasting days):

  • Irritable/cranky
  • Tired
  • Can’t concentrate
  • Dizzy
Your body learns what is feels like to be hungry Doesn’t work for families, as separate meals would need to be made for kids. Plus it exposes kids to the world of ‘dieting’ which can be dangerous in itself.
Great for those who don’t like sticking to a conventional daily meal plan It may encourage binging and restriction, which may be harmful to the mental state of many young men and women.
Good short term weight loss strategy for those who struggle on other plans. Doesn’t focus on any behaviour change to maintain weight loss after the first short period.
May work well for those who are busy and have constant distractions from eating. What is often overlooked in the media is that to be successful on this type of plan you still need to exercise regularly so you ‘huff and puff’, ie work on your cardiovascular fitness, eliminate or reduce alcohol on all days and be sensible on the other five ‘feast’ days.


CAUTIONS: This diet is not suitable for children, teens, pregnant women, the elderly, those with diabetes or on other medications – which is quite a lot of people now, and in particular athletes. Athletes would struggle to meet their pre/post training nutrient requirements on fasting days or simply would not have the energy to train at all!

THE VERDICT: Useful weight loss tool in the short term.

In essence if you don’t mind suffering through a couple days worth of hunger and all the symptoms that go along with that, then this style of eating may be a good short term weight loss strategy. To date, there still isn’t enough evidence in humans to claim that it prolongs life and prevents disease – since the weight loss that follows the diet may also be a large reason why these benefits are seen.

From what I can tell, intermittent fasting is just another way of getting people to eat less! It doesn’t specifically deal with the food challenges one faces on a daily basis, like the cookie jar at work, walking past the bakery or watching My Kitchen Rules or any cooking shown on TV. It is worth dialling into your internal hunger cues and listen to your body. I can’t help but think that people would still benefit just as much from eating a little less everyday and giving themselves a 10 – 12 hour break from food overnight. However if you do want to try this style of eating then please seek some guidance from an Accredited Practicing Dietitian.

Accredited practicing dietitian (APD) Katrina Mills was one of the accredited practicing dietitians who was featured in a podcast about the 5:2 diet. Click here for the podcast. Katrina is most likely to be found walking, swimming or hitting the gym if she’s not creating, cooking, eating or researching nourishing tasty foods.


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