Call for a consultation 07789 636 873

What is the ‘5:2 Diet’ and does it work?

I have found over the years that the 5:2 diet, is a fantastic way for people to lose weight and keep it off. It also has many other health benefits, and this article explains why I advocate giving it a try, whether you want to lose weight, or not.

5:2 Diet Robert Brennan

It is a type of ‘intermittent fasting’ and is simply eating what you would normally eat for five days of the week (no calorie counting), and then restricting calorie intake on two days, 500 for women and 600 for men. It is more of an ‘eating pattern’ than a diet, as it doesn’t formally prescribe what foods to eat.

I have found far greater results when clients, as well as observing the fast days, eat a generally healthy diet, free from processed foods and rich in vegetables and protein with plenty of water.

One of the reasons I think it works so well for people is that intermittent fasting is likely to have been a long standing feature in our evolutionary past due to the simple fact that food was not always readily available.


The primary benefit of the plan is that it reduces our long term average blood glucose levels, by making our bodies more sensitive to insulin.

In simple terms, overeating (especially carbohydrate) causes blood insulin levels to increase to restore the blood glucose level to normal. Repeated overeating leads to continually elevated insulin levels and cells become less sensitive to insulin. It is the tendency for people to become less sensitive to insulin as they age that leads to weight gain, rather than the common misconception that it is due to a ‘slowing metabolism’.

Once we are less sensitive to insulin, more insulin is released in order to remove glucose from the blood, which ultimately leads to Type 2 Diabetes. Insulin is an anabolic hormone (body building), so its continual elevated presence leads to body fat gain. This is why the 5:2 diet leads to weight loss.

Fasting is therefore a very simple way, alongside regular exercise and other heathy lifestyle factors, to keep insulin sensitivity higher for longer and maintain a healthy, lean body.

The 5:2 diet has also been shown to improve the balance of several other hormones such as leptin, for appetite regulation, and to reduce the level of growth hormone IGF-1, which is linked to various types of cancer and accelerated ageing.

There is also evidence of cognitive benefits such as increased concentration and focus, which is due to the increased presence of ‘brain-derived neurotrophic factor’ (BDNF), a chemical which enhances brain function, and also an increased rate of ‘autophagy’, the process whereby the brain cleanses and regenerates itself in fasting individuals.

Possible side effects

People may feel slightly dizzy, grumpy, or even anxious (if prone to it) on fast days, particularly at the start of the new eating pattern. This is due to the lower blood sugar level. It is usual for people to get used to the fast days however and these symptoms should not continue beyond the first few fast days.

For this reason in particular, it is not suitable for pregnant women, type 1 diabetics or elderly adults with health complications.

Some people have found it difficult to sleep on the fast days due to hunger, so it may be advisable to ensure that more of the calories are consumed later on in the day to avoid this.

These side effects will lessen as your body adapts to the new eating pattern, but it is wise to have a small snack to hand to pick up your blood sugars quickly if you need to.

Happy fasting!