Intermittent Fasting and the 5:2 Diet – what are they and why do them?

Intermittent Fasting and the 5:2 Diet are popular versions of the same thing – a short period of lowered calorie intake. 

Fasting basically means that you define a set period of time where you either:

  • eat nothing, or
  • eat very little.

Let’s look at two popular variations on this theme: Intermittent Fasting, and the 5:2 Diet.

Intermittent Fasting and the 5:2 Diet

There are many ways to do intermittent fasting, for example:

  • Eat all your meals between 9am and 5pm, then fast from 5pm to 9am
  • Eat all your meals between 12pm and 8pm, then fast from 8pm to 12pm.
  • Eat normally until Saturdays, when you only one meal that day at 1pm.
  • Eat normally until the weekend, when you eat only 500 calories per day.

You get the picture. You’re already doing a version of it every day – someone has just given it a fancy name, and put some rules around it.

The 5:2 Diet is a version of this – simply, eat very low calorie (25% of your normal intake) for 2 days per week and eat normally the rest of the time.

intermittent fasting and the 5:2 diet

Fasting Has Been Happening Longer Than You Think

Long before intermittent fasting and the 5:2 diet were a thing, fasting and/or temporal dietary restriction were practiced by a variety of different cultures and religions.

Think Ramadan, Lent, Vinaya, etc. It’s nothing new!

History and cultural reasons aside, there are emerging studies that indicate there are other reasons to take up intermittent fasting – namely, its various health benefits.

Let’s look at a few of those.

Intermittent Fasting for Weight Loss and Blood Pressure

Weight loss is an immediate and obvious benefit of intermittent fasting.

A meta-analysis of seven human IF weight loss studies conducted in the period 1975 – 20141 showed the following results:

  • Weight loss of up to 8.9% body weight, regardless of the fasting period used;
  • A decrease of up to 4% in blood pressure;
  • A decrease in insulin concentrations in half of the studies;
  • A greater compliance and lower drop out compared to ‘regular’ weight loss studies.


Intermittent Fasting for Athletic Performance, Memory and Immunity

A Sports Medicine paper2 references several longitudinal studies that demonstrate how fasting can improve physical and intellectual performance.

That paper speculates that the positive effects of fasting on our physiology and biochemistry could also be important for athletic success, improved memory and better immune function.


Hormone Regulation

As we know in the Downsize Me program, intermittent fasting has hormonal balancing benefits that actually cause the reduction in weight, cholesterol, triglycerides and body fat.

Those changes occur via changes in leptin, insulin and ghrelin3, 4, 5, among others.

And the latest research seems to indicate an important fact5 – fasting regularly over a longer period seems to be what really creates a difference in body composition and health.

How to Do Intermittent Fasting Yourself

It sounds easy, but in reality it’s not safe or appropriate for anyone to just jump in and do it. There are certain health issues that don’t combine well with intermittent fasting.

So before you do anything, check with your nutritionist, nutritional biochemist or naturopath to find out if fasting is right for you.

Some key elements of a safe and successful fast are:

  • Testing an intermittent fasting approach on one or two non-work days
  • A defined eating period within a 24 hour period – e.g. eating occurs within 6, 8, 10 or 12 hours of each day
  • Only do IF for one or two days within a 7-day period
  • Drink Lots of water and green tea – 2- 3L
  • Regular meals within the “eating window”
  • Getting adequate protein on the fasting days, from healthy sources
  • Nutrient-rich, brightly coloured vegetables

If you’re new to intermittent fasting and the 5:2 diet, you might like to download our 5-Step DIY Guide to Intermittent Fasting for Beginners….and let us know how you go!

Have you tried Intermittent Fasting yourself? Let us know about your experience in the comments below.


  1. Hankey, Klukowska and Lean, 2015. A Systematic Review of the Literature on Intermittent Fasting for Weight Management. FASEB Journal 29 (1), Supplement 117.4, April 2015.
  2. Cherif, Roelands, Meeusen and Chamari, K., 2015. Effects of Intermittent Fasting, Caloric Restriction and Ramadan Intermittent Fasting on Cognitive Performance at Rest and During Exercise in Adults. Sports Medicine Review Article, 46 (1), pp35 – 47, January 2016.
  3. Alzoghaibi, Pandi-Perumal, Sharif and BaHammam, 2014. Diurnal Intermittent Fasting During Ramadan: The Effects on Leptin and Ghrelin Levels. PLOS One 9 (3), March 2014.
  4. Mattson and Wan, 2005. Beneficial Effects of Intermittent Fasting and Caloric Restriction on the Cardiovascular and Cerebrovascular Systems. Journal of Nutr. Biochem 16 (3), pp 129 – 137.
  5. Tinsley and La Bounty, 2015. Effects of Intermittent Fasting on Body Composition and Clinical Health Markers in Humans. Nutrition Reviews 74 (7), September 2015.