Rainbow Diet

What is the Valter Longo Fasting-mimicking Diet (FMD)?

The Fasting-mimicking Diet (FMD) is a 5-day per month protocol, where you typically consume 34-54% less calories than usual, by cutting protein levels and inducing beneficial hormone changes; it is essentially a low-cal Mediterranean Diet.

The Fasting-Mimicking diet was originated by Professor Valter Longo stemming from his research at the University of Southern California Longevity Institute. By consuming a calorie restricted diet, yet maintaining the healthy fat protocol of the colourful Mediterranean Diet, the person following the protocol is still nourished by the diet, but gains significant benefits. At no point on the FMD do you ’fast’ completely. 

There is also a myth about the diet: most health experts report that it is a low carbohydrate, high fat diet. When you read the figures Longo suggests, you will realise that it is a low-calorie, low-protein diet! It has little or nothing to do with a Ketogenic diet. It is simply ‘a low-calorie due to low-protein’ Rainbow Diet.

ProLon for a Fasting-mimicking Diet? 

Unfortunately, there are many Websites trying to make money out of Longo’s work. The top 5 sites listed on Google, were all paid-for Advertisements! Longo himself helped originate a range of soups, bars and teas called ProLon when you spend your 5 days on the diet, but he personally does not receive financial benefit from this company. The ProLon products are criticised for being pricey.

There are a few slightly odd rules during the 5 day period – for example, vigorous exercise is forbidden. Unsurprisingly, you cannot consume any alcohol, but you can have a cup of real coffee.

Moreover, undertaking a 5 day fast each month is a ‘Health’ promoting exercise from the Longevity Institute yet the claim on the ProLon site is about weight loss – “In a clinical study, ProLon waas shown over three cycles (one per month for three months) to help individuals lose on average 5.7 lbs and 1.6 inches off their waist circumference.”

What is Intermittent fasting?

First, let us tell you what it is not. It is NOT ceasing consumption at 6 pm and starting again at 10.00 am. That is time restricted fasting. Many people get this wrong including so-called health experts. Time restricted fasting is primarily a weight loss programme where you are expected to consume maybe 60% of the calories of someone not on this time restricted eating pattern.  The research suggests that people on time restricted fasting cut their blood sugar and insulin levels, and that the weight loss comes with lowered cholesterol and cardiovascular benefits (1). Many people just do not stick to the diet and research has been mixed because of this.

Intermittent fasting is where you might eat for five days and stop for two days; or eat for 10 and stop for three or four. The FMD is a programme for 5 days per month.

Intermittent fasting is primarily about hormonal health changes. For example, different research studies at the Longevity Institute and elsewhere have shown that after 24 hours of a fast, your brain produces the health and longevity hormone Sirtuin 1. For example, this is a known and important regulator of several genes; it protects against a fatty liver and glucose intolerance; it reduces insulin and cholesterol levels: ity lowers glucose metabolism and it lowers the metabolism of cells in times of famine (1). Sirt 1 is associated with ageing, and the p53 gene. Increases in levels have important epigenetic functions and it can restrict cancer progression (2).

Research has also shown that fasting for several days can greatly improve the immune system (3) and stop cancer progression. Intermittent fasting can improve the action of chemotherapy and high dose vitamin C against cancer (4). 

Fasting has been shown to improve brain function and lower IGF-1 levels – the hormone is involved in cancers.

Intermittent fasting can greatly improve your health – reducing blood glucose and insulin levels, cholesterol levels, improving immune function and ‘resetting’ the body. 

Intermittent fasting is about repair.

What Foods can you eat on a 5-day fasting-mimicking Diet?

  1. Foods should be whole, not refined
  2. Day one should provide roughly 1100 calories, as 10 per cent protein, 56 per cent fat and 34 per cent carbohydrate. 
  3. Days 2 – 5 should provide 9 per cent protein, 44 per cent fat and 47 per cent carbohydrate. 
  4. Yes, really. The carb calories are usually higher than the fat levels, and it is the protein that is greatly restricted. Contrary to popular mythology, this diet has nothing to do with a ketogenic diet! 
  5. In the ProLon FMD packs, all foods are vegetarian, lactose- and gluten-free.
  6. The range includes supplements, herbal teas, soups like tomato and mushroom, algae oil, dark chocolate crisp bars, olives, kale crackers and nut bars. Oh dear.

The low-calorie Rainbow Diet – cut animal protein, cut alcohol, eat a little less?

Most people who adopt a strict high fibre, whole food colourful Mediterranean Diet lose weight anyway. The high fibre diet fills you up! It is highly nutritious and has a wide variety of foods in it. If you cut all animal protein and alcohol out for 5-days and ate a little less, you would almost certainly achieve the same benefits and more, without the expense. 

Go to:  The colourful Mediterranean Diet – Probably the healthiest Diet in the world 


  1. Mammalian Sirt 1; Cell Communication and Signalling; Shahedur Rahman et al; https://biosignaling.biomedcentral.com/articles/10.1186/1478-811X-9-11
  2. Sirtuin 1 and tumour development; Oncology Letters; November 16 2018: https://www.spandidos-publications.com/10.3892/ol.2018.9722
  3. https://the-rainbow-diet.com/the-colourful-mediterranean-diet/low-cal-mediterranean-diet-rejuvenates-the-immune-system/
  4. https://www.canceractive.com/article/fasting-plus%20vitamin%20c%20inhibits%20cancer%20progression

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