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Home » Diets that Work » The Right Chemistry: Intermittent fasting is hard. But does it work? – Montreal Gazette

The New England Journal of Medicine is widely regarded as perhaps the most prestigious medical journal in the world. It has an acceptance rate of five per cent, meaning that only one in 20 articles submitted is judged by experts to be worthy of publication. That doesnt mean the rejected papers are not based on sound research; most eventually get published in lesser journals. But the New England Journal looks for the cream of the crop. Thats why I pay particular attention to papers published in this journal, such as a recent article on the Effects of Intermittent Fasting on Health, Aging, and Disease. Even more so when the article is the work of Johns Hopkins University neuroscientist Dr. Mark Mattson, renowned globally for his research in the area of intermittent fasting.

Intermittent fasting does not mean cutting out a Snickers bar between meals. It refers to a systematic eating pattern that places emphasis not on what food should be eaten, but rather on when it should be consumed. Intermittent fasts fall into three general categories. In alternate day fasting, days of very low-calorie intake are alternated with days of regular eating. The 5:2 variety dictates eating normally on five days of the week but restricting calories to under 700 on two non-sequential days. In daily time-restricted feeding, all food is consumed in a six-to-eight-hour window, essentially resulting in a 16- to 18-hour fast. Most people who engage in this version finish supper by about 7 p.m. and do not eat again until lunch the next day.

Of course, the question is why anyone would want to engage in any of these torturous regimes. Simply put, it is because there is accumulating evidence that calorie restriction provides benefits beyond the obvious weight loss. It has long been known that reduced food intake in animals results in an increased life span. The assumption has been that the benefits of reduced calorie intake are due to a reduction in the generation of free radicals as a consequence of metabolic processes. However, it appears that there is another factor involved. Typically, in experiments in which rodents are put on a low-calorie diet, they are given their daily allotment of food in one dose that they generally consume within a few hours. This means that essentially, they are on a 20-hour fast. This results in metabolic switching, a term with which we have to become familiar to understand the benefits that are attributed to intermittent fasting.

The main source of energy for cells is glucose. During respiration, glucose serves as fuel, providing energy as it reacts with oxygen to yield carbon dioxide and water. It is this process that is also accompanied by the production of those troublesome free radicals. The main source of glucose are carbohydrates in the diet and when these are severely restricted, as in fasting, the body switches to fats as an alternate fuel. But fats are not used directly, they are converted in the liver to ketone bodies that then are metabolized yielding energy. This is commonly referred to as a state of ketosis.

It turns out that these ketones are not just fuel for cells, but are also signalling molecules that regulate the expression and activity of various proteins and other biochemicals that influence health and aging. It seems that metabolic switching, which is a result of periods of fasting, is perceived by the body as a signal to go into survival mode since no food is coming in. Cells respond by improving control of blood pressure and blood sugar, producing more antioxidants and curbing inflammation.

Most of the fasting studies that have produced promising results have involved animals, but some human trials are starting to emerge. Improvements in insulin sensitivity, verbal memory, resting heart rate, and cholesterol levels have been noted in short-term clinical trials. In rodents, experiments have shown reduced occurrence of spontaneous tumours with daily calorie restriction or alternate-day fasting. Suppression of the growth of induced tumours has also been observed. Furthermore, the animals show increased sensitivity to radiation and chemotherapy. Stimulated by these observations, a number of human trials examining the effect of intermittent fasting on breast, ovarian, prostate, endometrial, colorectal and brain tumours are underway. Pilot studies are also examining possible benefits of intermittent fasting in multiple sclerosis, rheumatoid arthritis, surgical outcomes and athletic performance.

Obviously, we have to temper this discussion with the all-too-often-stated disclaimer that more research is needed. But it is forthcoming. Dr. Valter Longo at the University of Southern California has some interesting results with his Fasting Mimicking Diet. For five days, people consume only special prepackaged foods that provide 1,000 calories the first day and 725 the other days and are said to have a unique combination of nutrients that trick the body into thinking it is fasting. Repeating the cycle monthly for three months has resulted in weight loss as well as a drop in blood sugar and cholesterol. But going hungry for five days is challenging and the meals are expensive.

It is always meaningful to ask experts what change they have made in their life as a result of their research. Mattson says he eats within a six-hour window every day. And thats from the horses mouth.

joe.schwarcz@mcgill.ca

Joe Schwarcz is director of McGill Universitys Office for Science & Society (mcgill.ca/oss). He hosts The Dr. Joe Show on CJAD Radio 800 AM every Sunday from 3 to 4 p.m.

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The Right Chemistry: Intermittent fasting is hard. But does it work? - Montreal Gazette

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Home » Diets that Work » The Right Chemistry: Intermittent fasting is hard. But does it work? – Montreal Gazette