Practising Fasting to Support Health and Prevent Disease

We may all have experimented with food abstinence for longer or shorter periods of time, but what do experts say about how to use fasting to really support health and prevent disease?


Our understanding of the impact of fasting on health, disease, treatment, and longevity is growing rapidly, especially thanks to the remarkable work of scientists such as Valter Longo, who went from studying food restriction on yeast cells and mice, to developing protocols in the clinical setting to support chronic metabolic conditions, including cancer. The results are quite impressive, and if you want to understand more of Dr Longo’s work and applications to human health we recommend his book 'The Longevity Diet' as a very interesting and entertaining reading.

Let's clarify that there are different approaches to fasting, and you may be familiar with different terms being currently used. Which approach to choose and for how long depends on individual characteristics, medical history, mind-set, and health goals. But if we try to simplify the picture on the basis of good evidence coming from clinical research/practice over the last 10-15 years, at least two main approaches have been studied in more detail in terms of health impact and cellular effects:


Fasting on an ongoing basis A very good practice to follow with some regularity is the so called ‘Time-Restricted Eating’ or TRE, which involves eating only during a certain time window within the 24 hours. A eating window of 12 hours (fasting for the remaining 12, fluids as needed) seems to provide the best results in terms #metabolic #profile #improvements (e.g. blood sugar regulation, improved blood lipid profile, weight loss, hormonal balance, insulin sensitivity, etc.), and it can be carried out safely by most people.

For some time now similar approaches to this have been given the collective label of ‘Intermittent fasting’, however this terminology is less favoured currently, because it ended up including all sorts of ‘fasting’ regimes, from hours to weeks, based on the perhaps misled assumption that any type of abstention from food would bring the same benefits.

Fasting for longer periods of time A rather different approach, and although abstaining from food has been practised for centuries in many cultures and traditions, extra care and supervision are advised because it is very important to consider the individual’s health status at the starting point.

HOW TO DO IT? It turns out that fasting periods varying between 3-5 days repeated every few months may be all we need to get the most benefits from the practice, as demonstrated in the case of Dr Longo’s ‘Fast-mimicking diet’ or FMD. Research into this approach showed that even just 3 cycles of FMD over 3 months clearly showed significant reductions in a number of risk factors for cancer, diabetes, and cardiovascular disease (e.g. reduction in blood glucose levels, increased body muscle/fat ratio, lower blood pressure, triglycerides, IGF-1, and inflammation markers; n=100).


More on FMD

FMD was developed to combine the observed benefits of fasting with requirements of safety and tolerance. So it's been designed to provide sufficient calories and nutrition to be safe outside a clinic, but it still ‘mimics’ the effects of full-on fasting.


It involves a period of very light food intake that lasts 3-5 days in which daily calories are restricted - between 300-700, depending on the individual. It is low in sugars and proteins, but it may include some healthy fats - may include broths, soups, juices, in some cases small portions of olives, nuts, seeds, all plant-based.


Cycles of FMD can be carried out every few months, and they can be adapted to the individual in terms of higher or lower foods/calories intake, but again this will all depend on the specific situation and health status.


Professional advice is always important, but it is highly recommended especially in the cases of people with existing health conditions (e.g. insulin-dependent diabetes), and especially when planning very low-calorie, or juice-only, or water-only versions of fasting, or fasting periods longer than 3-7 days.


Prolonged fasting regimes (>7 days) with minimal calories intake are also being studied in clinical settings and show promising results in terms of safety and beneficial health impact, but these are best conducted under medical supervision.


What happens during fasting and FMD?

We know this mainly from preclinical studies, but when combined with everything we are learning in actual patients, it is all quite exciting. FMD’s effects include switching all cells to an anti-aging mode by promoting #autophagy (i.e. self-eating of ‘faulty’ parts of the cell); replacing damaged cell components with newly-generated functional ones; killing damaged cells in many organs and systems (i.e.the immune system, pancreas, etc.), and replacing them with newly generated cells; shifting the body into fat-burning mode, which continues after returning to a normal diet, probably due to #epigenetic changes.


Quite a list of desirable effects. But, as emphasised above, fasting may not be for everyone, so if you have questions or would like to understand more on whether fasting may be helpful/safe for you, either get in touch with me or another qualified practitioner.


Photos by Dominik Martin and Lacey Williams on Unsplash

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Dr Silvia Grisendi PhD DipNT

T: 079 5076 1267

East Sussex, UK

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