Fasting has always been a part of human evolution. Back in hunter-gatherer days we would go prolonged periods without food, expending energy as we hunt our prey. It wasn’t until 10,000 years ago when agriculture emerged, going without food became less normal. However, fasting has never been truly absent in many cultures and religions: e.g. short fasting in Judaism’s 24-hour Yom Kippur, and Buddhism’s daily post-midday fast, to the prolonged 30-day dawn-to-dusk fasting for Muslims in Ramadan
Fasting- The science
In recent times fasting has become a hot topic amongst scientists and has fueled much research into the mechanism of associated health benefits associated with reduced calorie consumption and intermittent fasting (IF).
Back in 1945, a study in the Journal of Nutrition discovered that rats could increase life expectancy (20% for males and 15% for females). This was achieved by reducing calorie consumption with an intermittent fast of 1 day in 3 achieving best results.
Since this time there has been a variety of studies both in animals and humans to see how health and longevity were affected by IF. A review of such research in the American Journal of Nutrition found that IF modulated several risk factors, thereby preventing chronic disease in animals. Human trials to date have reported greater insulin-mediated glucose uptake. The limited human evidence suggests higher HDL-cholesterol concentrations (healthy cholesterol) and lower triacylglycerol concentrations.
Currently some of the reported benefits of IF:
So how do we explain the benefits of daily energy restriction (DER) and IF? A breakthrough came from a Japanese biologist Yoshinori Ohsumi who won the Nobel prize in 2016 for his work into autophagy (pronounced ‘or-toffa-gee’) – when pathogens (infectious agents), cell ‘junk’ or old and damaged structures are broken down inside a cell and the parts reused.
This is basically what happens in the body everyday as a byproduct of its metabolic processes. Otherwise known as “oxidative stress” it’s a bit like rust building up on your engine over time. It will inevitably happen unless we give our body an opportunity for essential maintenance. This is where autophagy kicks in and fasting taps into this process of cell repair and regeneration.
This is how physiologist believe it happens…
When we don’t eat for several hours the liver stops secreting glucose into the blood stream and instead uses it to repair damaged cells. Simultaneously the liver releases enzymes that break down stored fat and cholesterol. Hence during an (IF) our liver is repairing oxidative stress and burning fat.
The key is that what we eat, and when, affects this process. Sometimes what we eat pushes cells to keep multiplying and not recycle, called an anabolic state. Sometimes our body moves into a different state – one where we tidy up cells, kill off and recycle old ones. This is called the catabolic state, and it happens when we don’t eat. For optimal human health, the balance between anabolic and catabolic processes is crucial. Unfortunately this has been disrupted by modern society- readily available food sources, high-density calorific processed food and environmental influences such as marketing that promote regular snacking!
Putting Intermittent fasting into practice.
Michael Mosley has popularized (IF) with his books the 5:2 and the fast 800….
Time-restricted feeding (TRF): has been gaining popularity in recent years as perhaps an easier way of reducing the calories you consume every 24 hours. The basic premise is to only eat within a set period of time – anything from an 8 to 12-hour window being typical. In practice this means you finish eating after dinner at, say, 8pm – and you don’t eat again until 8am the next day (12-hour window for eating) or 12pm the next day (8-hour window for eating).
I have been trialing this 16 hour fast in every 24-hour period, as I am asleep for half and need only miss breakfast. From a compliancy perspective this is more realistic and the key for me is not to overcompensate in volume or quality. As previously reported I mainly stick to a Mediterranean diet, mainly plant based with fish, legumes, nuts (and red meat 1 -2 times week).
Finally for any eating plan to work it must be specific to your dietary needs attractive to you and sustainable for the long term. Certain Individuals should reframe from severe calorific restriction and fasting protocols. Michael Mosley has some guidelines, but best speak to your physician or qualified nutritionist/ dietician first.
Have you tried Intermittent fasting? If so what has your experience been?
I would love to hear from you J
Listen to Michael Mosley on RN podcast
Inflammation: a new approach to obesity and depression
Centenary Institute Oration recorded 16 September 2019