Fasting without fasting: key to beat diabetes and cancer?

By Marika Sboros

Fasting is as old the hills of ancient Greece. Mention just about any Greek sage you can think of: Plato, Aristotle, Plutarch, not forgetting the father of modern medicine, Hippocrates and maths whizzkid Pythagoras. All were dedicated followers of fasting. 

Fasting is not for the faint-hearted. In its classical form of no food or drink – except for water – for an extended period, it takes  commitment and discipline. (I’ve only ever managed to last eight days on water only.)

Below, a University College London neuroscientist looks at the power of intermittent fasting. Dr Nick Lesica says it’s ‘all the rage’ right now. Don’t even think of dismissing it as a fad. Research suggests it can give you the benefits of fasting without really fasting.

Lesica believes it may be a key to beating diabetes by restoring proper functioning of the pancreas. 

Prof Richard Feinman

Yet at heart, other experts say benefits are not only about calorie but also carbohydrate restriction. US biochemistry professor Richard Feinman and colleagues have done groundbreaking work on the subject.

In a study published in Science Direct in 2015, they make a clarion call for low-carb diets as the default approach for diabetes management. In a comment below Lesica’s article, Feinman makes the following points: 

“Twenty-six of us, clinicians with thousands of patients, other health providers, professors of biochemistry and other scientific fields provided a clear, peer-reviewed summary of why carbohydrate restriction should be the ‘default’ approach to type 2 diabetes and as adjunct to insulin (which would be reduced) in type 1.

“We documented that the diet has as good or better adherence as any other, improves diabetes even if weight is not lost but nothing is better for weight loss.”

However, doctors involved in researching and treating diabetes have never rebutted the article. They have simply ignored it.

That raises the question: “Why do they do it?” They’re doctors, after all.

“What could be so compelling as to not offer patients the best treatment? People say that they are owned by the drug companies but it doesn’t make sense. Probably owned by their own ability to admit mistakes but it still doesn’t make sense.”

“We do not think that we have all the answers but they refuse to engage in any professional interaction,” Feinman says.

Other research suggests that intermittent fasting and carbohydrate restriction may be keys to living with, rather than dying from, cancer. Here’s what Dr Lesica has to say:

By Nick Lesica, UCL

The Conversation – Intermittent fasting is currently all the rage. But don’t be fooled: it’s much more than just the latest fad. Recent studies of this kind of fasting – with restricted eating part of the time, but not all of the time – have produced a number of successes.

Dr Nick Lesica

But the latest involving diabetes might be the most impressive yet.

The idea of intermittent fasting arose after scientists were wowed by the effects of constant calorie restriction. A number of studies in many different animals have shown that restricted eating throughout adulthood leads to dramatic improvements in lifespan and general health.

The reasons for these improvements aren’t yet clear. Part of it seems to be that going without food gives cells in the body a much-needed break to perform maintenance and repair.

But the lack of food also forces cells to resort to alternative sources of energy. Some of these, such as ketones – molecules created in the liver from recycled fat – appear to be beneficial.

The problem is that constant calorie restriction isn’t practical. It’s easy for scientists to impose upon lab animals, but hard for humans to impose upon themselves in the real world.

Fortunately, we’ve learned that constant calorie restriction isn’t really necessary. Intermittent fasting seems to have many of the same benefits.

There are two main types of intermittent fasting. One type, known as “time restricted feeding”, requires eating only during a few hours of the day – say between 10 am and 6 pm. This approach gives the body a long break from food each night and also reinforces beneficial circadian rhythms.

The other type of intermittent fasting – made popular by the 5:2 diet – is known as “periodic fasting”. This approach involves alternating between long periods of unrestricted eating and short periods of eating very little (five days of eating normally, two days of eating restricted calories).

It isn’t yet clear whether one type of intermittent fasting is better than the other. But the data so far suggest that both types can work.

The recent studies of the effects of intermittent fasting on diabetes have focused on periodic fasting in particular. As a first step, researchers led by Valter Longo at the University of Southern California, began by testing whether periodic fasting could cure diabetes in mice.

Click here to read: Fasting: not just another F-word!


They used mutant mice that lack the fat hormone leptin to regulate their food intake. These mice constantly overeat and become obese and diabetic in early adulthood.

The researchers found that after just a few months of periodic fasting – alternating seven unrestricted eating days with four restricted days – the diabetes was cured.

This is an amazing result. But what’s even more amazing is the reason behind it.

The mice lost weight during the periodic fasting, which helped of course. But that wasn’t the whole story. Periodic fasting actually solved the problem directly at one of its sources: the pancreas.

Diabetes is a disease characterised by excess blood “sugar”, which really means excess blood glucose. It’s largely an insulin problem. Normally, insulin causes cells in the body to take in glucose from the blood. But with diabetes, glucose stays in the blood because cells no longer take it in. This is partly because many cells lose their sensitivity to insulin, but also because the pancreas stops making it.

It turns out that the periodic fasting made the pancreas start producing insulin again. The days of restricted eating gave the pancreas a break that allowed it to remove and recycle many of its cells. Then, when the mice started eating again, new cells that were capable of producing insulin emerged.

So the pancreas actually shrunk during the four restricted eating days, and regrew during the seven unrestricted eating days. After several such cycles of shrinking, recycling, and regrowing, the pancreas was nearly as good as new.

The big question, of course, it whether intermittent fasting will have the same effects in humans. The answer is not yet clear, but the initial indications from a recently published phase two clinical trial, again led by Longo, are promising.

In this study, 100 people went through a series of 30-day cycles of periodic fasting, each with 25 days of unrestricted eating and five days of restricted eating. After only three cycles, those subjects who started the trial with high blood sugar saw big improvements. And, importantly, none of the subjects in the trial experienced any harmful effects.

So the evidence in support of intermittent fasting keeps growing. Does that mean that we should all be doing it? Not necessarily.

It seems to be most beneficial for those who are already overweight and unhealthy. While it does also seem to have some benefits for lean and healthy lab animals, it’s not yet clear whether the same is true for humans.

The ConversationA much larger phase three trial of intermittent fasting in humans that will clarify a lot of things is set to begin soon. The results will no doubt be very exciting.

  • This article was originally published on The Conversation.
  • Follow me on Twitter @MarikaSboros
  • Like my Facebook Page
  • Sign up for email notifications of postings
  • Marika Sboros is co-author with South African scientist Prof Tim Noakes on a book documenting the background to his trial for advocating the science for low-carb, high-fat diets to treat and prevent obesity, diabetes and heart disease and the science for LCHF. The book will be published by Penguin Random House in November 2017.