The 5:2 diet: Scientifically proven benefits, or just another diet fad?

The 5:2 diet, also known as the ‘intermittent fasting diet’ is becoming a popular choice of diet, with celebrities like Miranda Kerr and Jennifer Anniston leading by example. It consists of consuming no more than 600 calories a day (500 for women) for 2 days a week (these are known as the fasting days), then eating whatever you like the rest of the week. I know many people who swear by this diet, saying it helps them lose weight, maintain a healthy weight and even aid digestive problems. It has also been said to speed up metabolism and even slow down ageing. But I wondered, is there any scientific support for its wonderful claims? Or is it just another fad?

Books on the 5:2 diet have become top sellers!
Books on the 5:2 diet have become top sellers!

The Scientific backup:

One way that this diet is said to work is by activating a gene, SIRT1, which has been found to stop fat being stored. SIRT1 has also been found to repair DNA and cells during fasting and was found to have anti-ageing affects, (Interestingly, Some of this was discovered in yeast cells!).

In experiments on mice doing the 5:2 diet, higher levels of BDNF were produced (it’s a fancy brain protein). This was found to improve learning and memory – suggesting that it may even help prevent Alzheimer’s disease (though this has not been studied in humans yet!!).

This diet has been found to increase the effectiveness of Insulin. Insulin is produced when we eat and stores excess glucose in the liver, this process is said to become more effective during intermittent fasting, which can reduce your risk of diabetes, heart disease and obesity.

Intermittent fasting has also been associated with a drop in levels of a hormone, IGF-1. Lower IGF-1 levels have been found to reduce risks of age related diseases such as cancer. This was tested on mice that were genetically engineered to not respond to IGF-1, and they lived twice as long! I doubt humans on the 5:2 will live twice as long, but there seems to be some decent backup for various health benefits that could potentially make us live longer.

The Problems:

  • Although there are some studies that have found this diet to be effective, this evidence is limited! Many of the claims of 5:2 rely on animal models, and only a few human studies have been done. This means that why it all seems at first like the answer to all of life’s problems, more studies need to be done to give it a bit more cred.
  • The subjects in studies where 5:2 has been effective didn’t binge eat and drink on the normal calorie days. It doesn’t look like you can have complete diet freedom on the 5 days you aren’t fasting; sadly it looks like you still have to show some level of restraint.
  • Finally, here’s a tip, if you know someone on the 5:2 diet and need to ask them a favour, don’t ask them on their low calorie days, you may not get a good result. Although there seems to be long-term benefits, the short term reality is that people can become cranky and easily annoyed on their fasting days, particularly when they first begin the diet.

So there we have it, the 5:2 is based on sound scientific ideas, but it needs a few more studies in humans until we can take all of its benefits as gospel.

Till next time,




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