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The question

I have type 2 diabetes and I’ve heard that intermittent fasting could cure me. Is this true?

The answer

In recent years, intermittent fasting has emerged as a novel way of treating patients with type 2 diabetes. There are anecdotal reports of patients who have lost weight, their blood sugar levels have improved significantly and they no longer need to take their diabetes medications. Their disease appears to be in remission – if not exactly cured.

However, endocrinologists – the doctors who routinely treat diabetes – as well as dietitians, are skeptical. They point to a lack of major studies that show this approach is effective and safe long-term. After all, intermittent fasting requires a big change in eating habits and it remains to be seen how many people can stick with it.

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Fasting, which involves not eating for defined periods, has been part of human culture for thousands of years. Most of the major religions encourage their believers to restrict food intake during certain times. But the use of fasting to treat diabetes is relatively new.

The idea has been popularized internationally by Jason Fung – a nephrologist (kidney specialist) and medical director of the Intensive Dietary Management Clinic in Toronto. Through a series of books and YouTube videos, Fung has attracted loyal followers who are convinced he has the answer to their diabetes problems.

Type 2 is the most common form of diabetes, accounting for 85 per cent to 90 per cent of cases. It usually develops later in life and it’s often associated with being overweight. A major feature of the disease is a condition known as insulin resistance. Insulin is a hormone that moves glucose (sugar), from the bloodstream into the body’s cells where it is used for energy. For a variety of reasons that are not fully understood, the body’s tissues don’t respond adequately to insulin and glucose then becomes elevated in the bloodstream.

Poorly controlled blood-sugar levels can lead to a host of medical complications, increasing the risk of heart attack, stroke, kidney failure, blindness and limb amputation.

Diabetes is often treated with medications to make the body more responsive to insulin. Some patients also take additional insulin to top up the amount produced by their own bodies.

Fung says he believes the medical community “has been treating type 2 diabetes incorrectly.” In particular, he argues that the medications used to clear sugar from the bloodstream end up overstuffing cells with glucose, which gets turned into fat. “Even if your blood sugar gets better, you gain weight and your diabetes is only getting worse,” he said in an interview.

According to Fung, cells are insulin resistant because they are already filled to the maximum with glucose. “Periods of fasting allow the body to burn off the excess sugar and then the cells become responsive to the insulin once again.”

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He also encourages patients to modify their diets by cutting back on refined carbohydrates which the body quickly converts into glucose and by adding healthy fats found in avocados, nuts and olive oil.

Once glucose stores are depleted, which happens after prolonged fasting, the body shifts to burning fat for fuel. Typically, people fast for 24 to 36 hours between meals. For example, if you eat breakfast on Monday, you wouldn’t eat again until the following day.

By fasting regularly, he says, patients tend to lose weight, their insulin resistance is overcome and they can cut back or even stop taking their diabetes medications.

“Type 2 diabetes is an entirely reversible disease,” he insists, challenging the traditional notion that it’s a chronic and often progressive condition.

Fung says patients with diabetes should at least give it a try. “If you don’t like it, or you feel unwell, you can stop immediately.”

But most doctors are unlikely to recommend intermittent fasting without more scientific evidence that it can produce lasting results.

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“We need a proper study with enough patients for a long duration of time to really prove whether this is safe and effective – or harmful,” says Jeremy Gilbert, an endocrinologist at Sunnybrook Health Sciences Centre in Toronto.

“All diets work in the short-term, but it’s the maintenance phase that’s so difficult,” he says.

There’s a risk that those who attempt it and fail could end up worse off, says Annie Hoang, a registered dietitian at Sunnybrook. An individual’s metabolism might switch into “starvation mode,” reducing the amount of energy needed at rest, she explains. That means some patients could regain all the weight they lost – and more – if they stop doing intermittent fasting.

Fung says he has personally treated more than 1,000 patients over the past five years “with many of them sustaining their non-diabetic status over the duration.” But he has not yet published in a peer-reviewed journal the data showing his patients’ actual rate of success.

Whatever the case, Gilbert says, “this diet has some extreme components, some of which makes sense, but it’s not clear how many people can actually do what [Fung] is recommending indefinitely.”

Paul Taylor is a Patient Navigation Advisor at Sunnybrook Health Sciences Centre. He is a former Health Editor of The Globe and Mail. Find him on Twitter @epaultaylor and online at Sunnybrook’s Your Health Matters.

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