If someone told you there was a pill that could help you look and feel younger, keep belly fat under control, reduce the risk of diabetes, cancer and heart disease, you’d be tempted to take it, wouldn’t you? Sadly, there’s no such magic pill, however, short periods of fasting can help you achieve all this, without the unpleasant side effects.
The unifying theory is that fasting helps to de-stress the body. By giving your body a break to catch up on all the things it doesn’t get the chance to do when it’s busy digesting and processing food, you may achieve health benefits. My approach on retreats and in my clinic is to guide people through a ‘block fast’ - a number of sequential days when the body is in an accelerated healing state, followed by personalised intermittent fasting protocols to use as part of a healthy lifestyle or weight loss plan. My version of block fasts use vegetables juices, broths and gut-health boosters as opposed to water-based fasts which are much harder on the body and can deplete nutrient levels. Many commercially available juices are simply too high in sugar, and not address the nourishment of the gut bacteria, vital to achieve the health outcomes.
Below you’ll find a brief explanation of how fasting is thought to exert its health effects all around the body, backed up by scientific research.
How does fasting affect blood glucose control?
Fasting has a beneficial effect on blood glucose control. One study, published in the Journal of Applied Physiology (Halberg 2005) showed that at end of an alternate-day fasting experiment over two weeks, insulin-mediated glucose uptake rates increased. In another study on overweight women, those who were restricted to 500 calories every second day (with normal eating habits in between) showed lower fasting insulin levels and less insulin resistance than those on a standard calorie-controlled diet (Harvie 2011). However, researchers at the National Institute on Ageing in the U.S. found that, when people ate only one meal a day in the evening for eight weeks, it seemed to take longer for their insulin levels to increase in response to a morning glucose load Carlson (2007). Similarly, Helibronn (2005) saw an impaired glucose response after eating in women (although the effects were beneficial in men.)
Who wants to live forever? (well, for an extra 40 years)
Let’s look at another hormone with a very similar structure to insulin. It’s so similar, it’s actually known as insulin-like growth factor, or IGF-1. IGF-1 has both positive and negative effects. Like insulin, it is anabolic, meaning that it tells our cells to grow. If IGF-1 is kept high, our cells are constantly dividing and multiplying - good if we’re trying to build big muscles; not so good if those cells become damaged and cancerous. High levels of IGF-1 have been linked to prostate cancer and postmenopausal breast cancer. When IGF-1 levels drop, the body slows production of new cells and starts repairing old ones - DNA damage is more likely to get fixed. The good news is that fasting also reduces levels of IGF-1. When the group of scientists in Calafornia genetically engineered mice to have low levels of IGF-1, they found that they lived 40% longer. It works on people to. a group of people in a remote region of Ecuador who have low levels of IGF-1 seem to be ‘immune’ to diabetes and cancer, despite having very unhealthy lifestyle. However, it’s not something that can be bottled, not yet anyway. The Ecadorians who have demonstrated this mind-boggling immunity have have a pre-exisiting condition called Laron Syndrome Laron Syndrome comes with growth problems, so it isn’t the magic answer.
In fact, the only way you can naturally reduce levels of IGF-1 is by fasting. Within 24 hours of fasting, IGF-falls. Fasting for three or four days, or cutting protein intake to below 0.95g/kg body weight/day, are the best way to get IGF-1 under control.
Fasting lets your body have a spring clean
Fasting switches on an important process, called autophagy. The term autophagy means ‘self eating’ and is describes how cells become enabled to identify and get rid of damaged or defective parts. For example, when a cell’s energy powerhouse the mitochondria become damaged they increase oxidative stress, intensifying the rate of cell damage. This is akin to power stations spilling out pollution. Autophagy enables the cells to get rid of the faulty mitochondria, allowing them to be replaced by more ‘energy efficient’ new ones. It also helps the body fight infections and recover from injuries. Autophagy is increased whenever we are fasting, whereas eating even small amounts reduces it. Studies have shown that eating as little as 10g of essential amino acids (found in high quality proteins) can switch off autophagy. A juice fast may well be the answer if you want to give your body a good ‘spring clean’ because juices are typically very low in protein. Now, autophagy and IGF-1 are two things that you neither want to be ‘on’ all the time or ‘off’ all the time. They key, like in most things, is finding the right balance.
Fasting reduces inflammation
Inflammation is a normal response to injury, aimed at removing whatever’s causing the injury and kick-starting the healing process. But too much can be dangerous, as is the case in inflammatory conditions such as arthritis, atherosclerosis and even eczema. High levels of body fat are associated with increases in inflammatory markers such as IL-6, TNFa and CRP. Studies on several different fasting formats show that these inflammatory markers tend to reduce during periods of fasting. This is the case for Ramadan (a daily fast of 12-18 hours), a single daily meal versus three meals a day, and for alternate day fasts. (studies by Aksungar, Dixit and Johnson). Intermittent fasting has been specifically shown to reduce the symptoms of asthma, another condition in which too much inflammation plays a key role.
Fasting helps keep the heart and circulation healthy
Inflammation is involved in cardiovascular disease, in concert with high levels of ‘bad’ fats in the blood. Most studies on fasting show that they reduce triglyceride levels and improve the ratio of triglycerides to ‘good’ cholesterol (HDL - the transport protein that helps remove excess cholesterol from the bloodstream). In animal studies, resistance to what is known as ‘ischaemic injury’ - the type of artery damage that’s associated with the build up of plaques and hardening of the arteries, has been seen.
All in all, fasting seems to give the body an internal tune-up and increase resistance to age-related illnesses.
Fasting resets constant snacking
If you are someone who eats all the time then you may have chronically high insulin levels. Insulin provides the signal to your body to store energy from your food so that it can be accessed later. It basically acts by unlocking cells and allowing individual molecules of glucose to enter. It also tells the cells to make more protein and fat and to keep the existing fat locked away inside.
This is all designed at keeping the levels of blood sugar within a tightly-controlled range. Any sugar that isn’t immediately required for energy has to be stored in the muscles or liver.
High levels of insulin in the body can increase the risk of insulin resistance (those locks gets ‘broken’ and start having difficulties recognising the ‘key’.) Over time, insulin resistance increases the risk of diabetes, and has also been linked to cardiovascular disease, cancer and other inflammatory health conditions.
The idea of eating “little and often”, which is promoted by so many diets, is about preventing your body from releasing too much insulin at once and only giving it the nutrients that it can immediately put to use. But in order to burn off body fat, your insulin levels need to be low.
So, if you eat little and often, your body will always be releasing a little insulin. Increasing the gaps between meals through fasting means that you will get a spike in insulin after eating, then a longer period of time where insulin isn’t involved at all. The idea is that this will not only encourage your body to burn fat, it will also help maintain its natural sensitivity to insulin.
