Andreas Michalsen has a new book: The Nature Cure: A Doctor’s Guide to the Science of Natural Medicine.

His August 1, 2019 Wall Street Journal op-ed “The Fasting Cure Is No Fad” is, I assume, a teaser for his book. And that teaser for his book is all about fasting.

In addition to weight-loss, as a doctor, Andreas uses fasting to help his patients with “diabetes, high blood pressure, rheumatism and bowel diseases, as well as pain syndromes such as migraines and osteoarthritis.” He typically tells his patients to restrict themselves to no more than a ten-hour eating window each day. (In “Miles Kimball on Diet and Health: A Reader's Guide” I have links to many blog posts about fasting. I also recommend Jason Fung and Jimmy Moore’s book “The Complete Guide to Fasting.”)

Andreas lists many positive effects of fasting. Let me give a theory about how they all hang together. I’ll bet that in the environment of evolutionary adaptation our ancestors lived in before the advent of agriculture, involuntary fasting—that is, periods of time with little or no food—were quite common. As a result, many of our bodies’ systems were designed in a way that took as given that there would be frequent periods of little or no food. When people eat all the time, these systems don’t work very well.

As an analogy, think of how much the design of typical kitchen tools depends on the assumption that there will be gravity. A regular cutting board or a typical mixer wouldn’t work so well on the International Space Station! For most of our activities we take gravity for granted. And, for the most part, evolution could and often did take the existence of frequent periods of little or no food for granted—for us as well as for many other animals.

Here are some body systems that seem to work better with fasting. In the indented passages that follow, my labels are in bold; reference to relevant blog posts are in italics; the remainder of the words are Andreas’s.

• Preventing Diabetes and Liver and Pancreas Disease: Satchidananda Panda … fed a group of mice a high-fat diet around the clock for 18 weeks; they developed fatty livers, pancreatic disease and diabetes. Another group was fed the exact same number of calories a day, but all during an eight-hour span. Surprisingly, the second group stayed slimmer and healthier for much longer. (See “Obesity Is Always and Everywhere an Insulin Phenomenon.”)

• Recycling: When we eat, our body releases insulin. That disrupts the process of autophagy (from the Greek, meaning “self-devouring”), by which cells deconstruct old, damaged components in order to release energy and build new molecules. Autophagy helps to counteract the aging of cells and builds immunity. Fasts stimulate autophagy and allow the full molecular process to take place, as a team led by Frank Madeo at the University of Graz in Austria found in 2017.

• Producing Brain-Derived Neurotrophic Factor (BDNF): Fasting also can contribute to brain health and happiness. The neurobiologist Mark Mattson, who retired this year from the National Institutes of Health, has demonstrated in experiments for two decades that nerve growth factors contribute significantly to brain health and positive mood. He also found that fasting, restricting calories and exercising spur distinct increases in the best-known nerve growth factor, BDNF.

• Preventing Parkinson’s, MS and Alzheimer’s: Test animals in Dr. Mattson’s laboratory that fasted intermittently even showed a significantly lower risk of developing Parkinson’s disease, multiple sclerosis and Alzheimer’s, though those results would have to be clearly confirmed in large human studies to reach any firm conclusion. (See “Jonathan Shaw: Could Inflammation Be the Cause of Myriad Chronic Diseases?” and “Hints About What Can Be Done to Reduce Alzheimer's Risk.”)

• Preventing Cancer: Fasting might even be effective in preventing the recurrence of cancer, as suggested by initial results of an epidemiological study conducted by researchers at the University of California at San Diego, published in 2016 in the journal JAMA Oncology. Among 2,400 women with early-stage breast cancer who provided information on their eating rhythm, roughly 400 suffered from new tumors within seven years. But women who fasted for 13 hours nightly had 26% less risk of recurrence than the control group. One possible reason was suggested in data summarized last year from a decade of animal experiments by Valter Longo and a team at the University of Southern California: Cancer cells are less able than normal cells to survive a lack of sugar. (See How Fasting Can Starve Cancer Cells, While Leaving Normal Cells Unharmed, “Why You Should Worry about Cancer Promotion by Diet as Much as You Worry about Cancer Initiation by Carcinogens,” “Good News! Cancer Cells are Metabolically Handicapped,” “How Sugar, Too Much Protein, Inflammation and Injury Could Drive Epigenetic Cellular Evolution Toward Cancer,” “Meat Is Amazingly Nutritious—But Is It Amazingly Nutritious for Cancer Cells, Too?” and “My Annual Anti-Cancer Fast.”)

For annotated links to other posts on diet and health, see “Miles Kimball on Diet and Health: A Reader's Guide.”