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Could 7 Days Of Fasting Protect Against Cancer?

Is it really possible to dodge the Big C just by not eating for seven days? Dr Jason Fung, author of The Complete Guide To Fasting, thinks so

Fasting is an obvious, if extreme, way to lose weight. And we know, because one of the RISING team tried it, losing 30lbs in 31 days. But science has also discovered that fasting can help the body’s cell regeneration process, which in turn means it could help prevent cancer. Put down that burger, right now!



RISING Let’s cut to the chase. Can fasting for one week per year protect against cancer?

JASON FUNG ‘The idea comes from professor of biology Dr Thomas Seyfried, who believes fasting can target the inflammation that contributes to the initiation and growth of tumours. His experiments found that fasting massively reduced “tumour invasion” in models of brain cancer.’


RISING So, is it just one doctor saying this?

JF ‘No. A lot of research has uncovered a dramatic drop in inflammation, among other things, with fasts of three-to-five days. Fasting induces self-cleaning mechanisms called autophagy and apoptosis, which are thought to reduce the chances of developing cancer.’


RISING Apo-what-osis?

JF ‘Apoptosis, which is also known as “programmed cell death”, is when cells commit suicide. It sounds kind of macabre, but it’s essential for good health. The cells of the body are like cars. When they get too old to be repaired they need to be destroyed to make way for healthy new cells – up to 70 billion every day. Not all cars need to be scrapped, though. Sometimes you can replace the parts, and this is where autophagy kicks in. The word derives from the Greek ‘auto’ (self) and ‘phagein’ (to eat), so literally means ‘to eat oneself.’ It’s when a cell doesn’t die, but replaces the worn out ‘sub-cellular’ parts with new ones. Autophagy is a form of cleansing: the process of breaking down and recycling cellular components when there’s no longer enough energy to sustain them. Once all the broken-down parts have been cleansed, new tissues and cells are built to replace the old ones. So, our bodies are in a constant state of renewal, but when these processes are hijacked, unwanted cellular bits build up and diseases such as cancer occur. Increased levels of glucose, insulin and proteins all turn off autophagy, and it doesn’t take much. Even as little as three grams of the amino acid leucine can stop it. But fasting turns these cleaning mechanisms on.’


‘Cells are like cars – when they get old they need to be destroyed – up to 70 billion every day’


RISING How does that work?

JF ‘When we eat carbohydrates or protein, insulin is secreted. Increased insulin levels and the amino acids from the breakdown of protein tell the body that food is available. It decides, because there’s plenty of energy to go around, that there’s no need to eliminate the old subcellular machinery. In other words, the constant intake of food, such as snacking throughout the day, suppresses the renewal processes.’


RISING So, this increases the risk of cancer?

JF ‘When the body senses the temporary absence of nutrients, it must prioritise which cellular parts to keep. The oldest and most worn-out cells get discarded, and amino acids from the broken-down cell parts are delivered to the liver, which uses them to create glucose during gluconeogenesis – a natural process in the body that helps to maintain stable blood sugar levels. Cancer may be a result of what’s called ‘disordered autophagy’. We’re learning that this process plays a role in cancer biology, and products that inhibit this process have been approved by the Food & Drug Administration in the US for the treatment of cancers. Fasting’s role in stimulating autophagy provides an opportunity to prevent cancer. And that’s why Dr Seyfried proposes a yearly seven-day water-only fast.’


RISING Seven days with no food, just water?

JF ‘Distilled water, to be precise. No additives, no vitamins, no minerals. Distilled water and nothing else.’


RISING That sounds intense – earlier on you said three-to-five days. So why seven?

JF ‘We don’t yet know for definite how long it takes to reduce insulin levels and increase autophagy, and it may be different for everyone, so it’s probably best to give fasting a few extra days to make sure you’re getting the protection you need. If you drink plenty of water, you won’t feel hungry after a couple of days.’


‘Fasting’s role in stimulating cleansing provides an opportunity to prevent cancer’


RISING Does that mean I can eat whatever I want when the week’s up?

JF ‘No. Fasting isn’t a cure-all – healthy eating still matters. Modern medicine’s greatest challenges are metabolic diseases: obesity, type 2 diabetes, high blood pressure, high blood cholesterol and fatty liver, collectively known as metabolic syndrome. The presence of any of these diseases massively increases the risk of heart disease, stroke and cancer. That means premature death. And the roots of metabolic syndrome lie in the Western diet, with its abundance of sugar, high-fructose corn syrup, artificial flavours, artificial sweeteners and over-dependence on refined grains.’


WHAT NEXT? Now you know the benefits, could you fast for a week? You’d need to check with your doctor first and being underweight or having health issues are red flags, but you could start off by trying it for three days. The first 48 hours are the toughest, but after that point your body will enter a process called ketosis, where your body starts burning its own fat stores for fuel. So, as long as you drink enough water – at least two litres per day – you won’t feel hungry. If you, like the RISING guinea pig, find that after three days you have more energy, feel more alert and have shaken off the sniffles, then seven days could be a breeze.


Advice is for information only and should not replace medical care or recommendations. Please check with your Doctor before embarking on exercise or nutrition regimes for the first time.