The 5:2 diet: good, bad or ugly?

The 5:2 diet is a new craze popularised by the telegraph newspaper supposedly promoting: weight loss, a longer life and immunity to cancer. You consume in essence what you want for five of the seven days in a week and the diet kicks in for the other two days. These two days can come in any order but usually precedes a normal eating day. During the two days, you limit your calorie intake to a mere 500 for women and 600 for men.

I’ll address the question that has diverted your attention away from the main theme of this article- how does it make you immune to cancer? When the body is starved, it enters survival mode- it stores what it can. Cancer however, cannot do this, so you are starving the cancer cells but not starving normal cells. Autophagy is the process where cells ‘clean up’ cellular rubbish, fasting induces profound autophagy (neuronal and general) and therefore it protects cells from the cancer.

What about just simply fasting? Fasting significantly lowers the amount of insulin in your body and a high level of insulin (more specifically insulin growth like factor 1) in the body has been linked to an enhanced cancer risk. The telegraph used the work of Professor Longo who looked at a remote population of people (fewer than 350) who do not produce IGF-1. Of these people not a single one had died of cancer. That works out to be a 350 (and counting) to 1 chance of contracting cancer for the IGF-1-less people. Numbers produced by cancer.org suggest males have a 1 in 4 chance of dying from cancer, females a 1 in 5. So, ignoring their appearance, ‘short, typically less than 4ft tall, with prominent foreheads and underdeveloped jaws’ the Laron syndrome suffers are exactly the same as everyone else, but have a much lower chance of contracting the deadly disease.


The pressing issue with a fasting diet is that cutting down calories means one major food group will suffer, either: fats, protein or carbohydrates. All of these are essential because the body looks to use fats, then carbohydrates, then protein. Cut down on fats or carbohydrates and the body uses protein quicker and takes more to compensate. Why is this a problem? Well, if IGF-1 definitely causes cancer and carbohydrates start this process, they would have both been eliminated years ago. Research from the Harvard gazette archives referring to IGF-1 found that, “a protein that binds to the growth factor seems to neutralize it and reduce the risk of these malignancies”. The reason not everyone who eats a potato contracts cancer is because the IGF-1 is neutralised by one of the six binding proteins (IGF-BP). If you allow your body to use up all of this protein because it is compensating for a decrease in fats or carbohydrates you are taking away your IGF-1 neutraliser and your cancer neutraliser. Simply decreasing the amount of protein you eat produces the same result just a lot quicker!

However, there are some of negatives of the 5:2 diet, autophagy as mentioned earlier relies on lysosomes and reactive oxygen species (ROS). Obviously ROS relies on oxygen (hence the name) and although this oxidation does destroy cells and stop cancer it can also cause chronic diseases according to Kiffin, Bandyopadhyay and Cuervo. Also, once the cancer cells are developed they may engage in autophagy to help the tumour grow in times without nutrients- Kiffin once again providing us with the research. This evidence suggests both healthy and unhealthy patients will be affected by the autophagy process.

Work produced by the telegraph and Dr. Varady shows benefits after 10 weeks of fasting under the 5:2 regime. One group was encouraged to eat low fat foods; the other group took part in the two day fasting programme (eating pizzas and lasagnes on their non-fasting days. Vardy’s study showed the 5:2 group lost the same if not more than the low fat group over the 10 week period. Of the two diets, from a health and not weight loss perspective- the 5:2 diet is much better. The low fat diet obviously neglects the body of fat (often deemed the way to lose weight) which can have catastrophic consequences. Work by the Cambridge nutrition clinic has proven that fats and cholesterol create and protect the white blood cells whereas a lack of fats can cause damage to arteries and veins as well as, heart attacks, strokes and organ failure.

Whichever way you look at it: restricting carbohydrates has strong benefits (low IGF-1) as well as strong consequences (use of protein faster). A low fat diet obviously lowers your body fat and you will lose weight, but as a result your immune system will suffer and the long term damages can be deadly. A fasting diet has been shown to reduce the chance of cancer and increase it at the same time. All restrictive diets have positives and consequences. The body may in the short term show benefits from cutting one of the seven food groups from your diet but, in the long term they are there for a reason! It may sound old fashioned but, exercise and a good balanced diet will always be best for you.

Research will carry on for thousands of years with new innovative diets and products and they will value and devalue each other but I guarantee, exercise and a good diet will never be devalued- fact. I do however have one little cheat- the exercise you have to do to lose weight is very, very light. Losing weight relies on working ‘aerobically’; this requires you working at roughly 65% of your maximum heart rate (220-age). A 20 year old for example will work at 130 beats per minute (BPM) which if you actually try it, is a very moderate jog. Doing this for per say 40 minutes a day, 3 days a week will show massive weight loss. The toning comes from working anaerobically which, granted, is hard work, but the initial weight loss phase is (to be brutally honest) easy.
To conclude, this article focused on the 5:2 diet so, does it work? Research shows it most definitely does work however, there is some research that suggests there are dangerous consequences- all be it very extreme and rare. It has to be considered the best diet out there at the minute for sure, but all restrictive dieting programes have consequences and for that, it has to be dubbed ‘the best of a bad bunch’.