By LIZ HUNT
We usually think of fasting as a weight loss measure, but advocates say it has therapeutic benefits too.
Francoise Wilhelmi de Toledo combines a passion for her subject with a precision one would expect of a doctor and scientist with a raft of publications to her name.
"Real medicine is lifestyle. It is how we live," she says. "Drugs, any drugs, must be complementary to that."
As medical director of the renowned Buchinger Wilhelmi Clinic in Germany, she is an authority on therapeutic fasting and responsible at least in part for the current interest in its role in the management of chronic diseases including obesity, diabetes, high blood pressure, high cholesterol and cancer. And, of course, as a means of weight control made popular by the diet du jour, the 5:2.
The capacity to fast derives from periods when our ancestors ate more than they needed and built up fat reserves for winter when access to food was reduced.
Fasting – as part of a lifestyle – is undoubtedly a good thing, she says, but her focus is on making it part of the armamentarium available to doctors coping with an epidemic of lifestyle diseases in the West that threaten to cripple healthcare systems.
She says there is strong evidence gathered over many decades to show how it can lower blood pressure, reduce excess fat and glucose in the blood, modulate the immune system, increase the effect of the mood and sleep-regulating neuro-transmitter serotonin, boost protein repair, and reduce inflammation.
Fasting has been likened to a "reset" button that returns the human body to its – healthy – factory settings. A study published last year in the United States, drawing on animal and human trials, concluded that three days of fasting can rejuvenate the immune system, triggering the production of new white blood cells. Other studies show that fasting can enable healthy cells to endure better the toxic impact of chemotherapy while cancer cells die more rapidly. It is a fascinating area of research that draws on the body's evolutionary adaptation.
"Human beings are not programmed for abundance," de Toledo says. "Humans are programmed for loss." The capacity to fast derives from periods when our ancestors ate more than they needed and built up fat reserves and surplus nutrients, such as vitamins and minerals, in summer and autumn.
In winter and spring, when access to food was much reduced, they endured periods of fasting in which their metabolism switched automatically from "external nutrition to nutrition taken from fat reserves".
In the absence of carbohydrates as a source of energy (glucose) for the cells, fatty acids, from fat supplies, were broken down in the liver to produce molecules known as ketone bodies which were used for fuel instead.
Of course we retain this ability to fast and exist on a ketogenic diet but rarely use it in the affluent West because food shortages are largely unknown. Nor is there much incentive to invest in fasting research, despite preliminary evidence that it may help in Parkinson's, multiple sclerosis and Alzheimer's. In Russia, there is a vast, largely unexplored archive built up by a psychiatrist Dr Yuri Nikolayev, who used fasting or "the hunger cure" to treat a range of mental disorders.
This lack of interest frustrates de Toledo.
"Take type 2 diabetes," she says. "This is a disease we know that we can cure [through fasting]. But there is an industry that sells all these drugs and devices. We have a type of medicine [in fasting] that is highly successful but there is no return on investment."
It was as a 17-year-old in Geneva that de Toledo embarked on her first fast with the aid of a book, because she "was at odds with my weight and wanted to match the ideal of the slim beauty". She says it was a revelation, that she felt "buoyant, sometimes euphoric" while fasting.
She says people who turn to fasting include some seeking help for intractable health problems while for others weight loss is the primary goal. Many, however, are seeking respite from stress of work in the "spiritual dimension of fasting" that de Toledo claims is one of its most beneficial side effects.
She still fasts twice a year, during a 12-day annual retreat, and to counteract a severe seasonal allergy to birch pollen. She says suspicion and cynicism about fasting is still rife among doctors and nutritionists and she is determined to challenge it. "We want to document and show that fasting is therapeutically efficient, safe and enjoyable," she says.
The science, it would seem, is increasingly on her side.