5:2 - Is it for you?

Learn more about the 5:2 diet and how it works

What's all the fuss?

Everyone is talking about the 5 and 2 diet since it's coverage on the Sunday Night program two days ago. There are news articles, blogs, forums, tweets and any other communication medium filled with this diet, and whether it is the answer to losing weight and living longer.

I have been asked by two clients about the diet, and whether it is something we need to incorporate into their program. I said no to both of them, not because I have anything against the 5 and 2 diet, but because they are making great progress on their current program! Why mess with that?

I watched the Sunday Night program today (Tuesday afternoon, is that allowed?) and the story was quite interesting. Dr Michael Mosley is quite convincing in his argument that this diet will make you lose weight and live longer (doesn't want to do that!?).

However, I'm not convinced that this diet is the answer for everyone trying to lose weight. More importantly, I think it can reinforce bad nutrition habits and cover them up with some weight loss. So read on for my explanation and thoughts of the 5 and 2 diet.

How does it work?

Maths - the uncool reality of being a Nutritionist.

Maths - the uncool reality of being a Nutritionist.

Just like any other diet or nutrition protocol to lose weight, 5 and 2 works by creating an energy deficit (less energy coming in than going out). Where 5 and 2 varies is that instead of creating an energy deficit on a daily basis, this deficit is created over a week.

To illustrate this, I visited the 5 and 2 website and used their calculator to determine how I would do the diet. Note that my daily energy requirements was estimated at ~3000 kcals/day, which is about what I consume now.

I require 3000 kcals per day to maintain my weight. This equates to 21,000 kcals per week.

The 5 and 2 diet involves eating normally 5 days per week and eating one-quarter of this intake on two other days. My weekly estimate intake on this program would look something like this...

(5 x 3000) + 2(0.25 x 3000) = 16500 kcals per week on the diet.

This gives an energy deficit of 4500 kcals (21000-16500) which should theoretically support weight loss, since this is below my estimated requirements to maintain weight.

If I didn't want to do the 5 and 2 diet, but wanted to create the same energy deficit on a daily basis, my energy intake would be calculated like this.

16500/7 = 2357 kcal/day.

I generally recommend starting with about a 500 kcal deficit per day to support weight loss, which in this case would be 2500 kcal. The 5 and 2 estimate slightly lower, but not too far from this. In this aspect, the energy deficit it quite similar to many other diets or nutrition protocols with the same goal. 

For me personally, I would rather eat 2357 kcal every day of the week, compared to eating 3000 kcal five days per week and more importantly, 750 kcal twice per week. But other individuals might be different, which is important to acknowledge.

Why is the 5 and 2 diet so attractive?

Simplicity. In nutrition the simple plans are often the most popular. 'Eat 5 days per week and fast 2 days per week', in theory, it's a very simple protocol. The same goes for low-carb diets, all you need to do to follow the plan is avoid carbs and it will supposedly work it's magic (short-term at least). It also means there is only one aspect to focus on, meaning it requires less attention and focus through through the day, which we like!

5 and 2 makes you live longer.

The diet has only been around for a few years, so there is no evidence from human studies to support this statement. However, there is also no evidence to prove it wrong, so believe what you want. The proof will come when Dr Michael Mosley lives to 150 years of age and becomes a Mutant Ninja Turtle. If and when this happens, I will unashamedly become the number one advocate for this diet!

Teenage Mutant Ninja Turtles - In cinemas now.

Teenage Mutant Ninja Turtles - In cinemas now.

Our ancestors led a feast and famine lifestyle, aren't we are genetically wired to do so?

Maybe they did lead this lifestyle or maybe they didn't. The typical example is they feasted only when they caught wild animals and fasted when they didn't. However, our ancestors also gathered food, which does not involv catching a moving animal. Did they save this food up until they caught the animal to make a better feast? Or would they eat this everyday? I'm not sure...

You only need to exercise for three minutes per week.

I am not convinced of this idea. I am aware of the benefits and research surrounding Tabata training, and this may be the research referred to for this diet. While you might get the a decent improvement in aerobic workload and burn some energy, this protocol is not well rounded or suited to every individual. I'd also be surprised if you can build lean muscle tissue in only three minutes of exercise per week, which is often and important goal for people looking to improve their physique.

More importantly, high intensity exercise is a contraindication with overweight and obese individuals. Overweight and obese individuals are more than likely the people who will be using a diet such as this, so I would be wary of promoting this exercise style early on.

5 and 2 Doesn't Address the Issue.

I can't solve these...

I can't solve these...

I could go on about this point forever, and I might have to write a separate blog post about it. People aren't overweight because they eat food, they are overweight because they make poor nutritional choices and eat too much of it. Too often, we ignore this fact and take the wrong approach to solving this issue. 

The issue with 5 and 2 diet, is that there is no direction to improve food quality. Instead, the message is to reduce food intake. This is the equivalent of playing with the Rubik's cube above, and then hiding it away on two days of the week. Sure, the cube is no longer a problem you have for that day, but you haven't solved it either...

I would rather see people consume more quality sources of food instead of severely restricting food intake two days per week. I think this will help create a better relationship with food and promote nutritional independence. 


I am neither for or against the 5 and 2 diet. I think that it offers a simple nutritional package that is easy to follow (in theory, at least). However, I don't think it works to solve individual's nutrition problems and I wonder about it's suitability/adherence for most people.

Do you agree or disagree? Leave a comment below, tweet @integratedFN or find us at facebook.com/integratedfitnessnutrition