© Illustration: Gwenda Kaczor

The regimen lowered the levels of inflammatory factors in their blood and factors accelerating the aging process, including insulin.

New research is showing the profound benefits — for weight, longevity and fighting disease — of eating only during limited hoursFasting is one of the biggest weight-loss trends to arise in recent years. Endorsed by A-list celebrities and the subject of a spate of best-selling books, it was the eighth most-Googled diet in America in 2018.But fasting shouldn't be dismissed as just another fad. At the Charité University Hospital in Berlin, I've employed what's called intermittent fasting, or time-restricted eating, to help patients with an array of chronic conditions. These include diabetes, high blood pressure, rheumatism and bowel diseases, as well as pain syndromes such as migraines and osteoarthritis.The biologist Satchidananda Panda at California's Salk Institute showed the possibilities of this approach in a 2012 report in the journal Cell Metabolism. He 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.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.All of this presents a question: If we should generally eat only two meals a day, which meal is it best to skip? Many of us have heard the saying: "Eat breakfast like a king, lunch like a prince and supper like a pauper." Scientific evidence for the glory of breakfast is scarce, however, and realistically, it's easier to sustain skipping breakfast than skipping dinner.Instead of breakfast, we should eat lunch like kings. A rich lunch beats a robust dinner. A U.K.-led study published in the American Journal of Clinical Nutrition in 2016 showed that among 69 women, those who consumed most of their calories at lunch shed 3.3 pounds more in 12 weeks than those who ate a bigger dinner. After all, it's around lunchtime that the body requires the greatest amount of energy for keeping its body temperature up. Less energy thus passes into our fat reserves.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. 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:As a practice, fasting is more than simply restricting calories or nutrients. For many people, it is also a spiritual experience. Over the course of our lives, we encounter many kinds of deficiency, whether of money, success or affection. Fasting is a conscious renunciation, a controlled exercise in deprivation. That's why successful fasting increases self-efficacy — we overcome an instinctive need in a way that gives us physical and mental strength. In his novel "Siddhartha," Hermann Hesse describes this wonderfully: "Nothing is performed by demons; there are no demons. Anyone can perform magic. Anyone can reach his goals if he can think, if he can wait, if he can fast."Dr. Michalsen is a professor at Berlin's Charité University Medical Center. This essay is adapted from his new book, "The Nature Cure: A Doctor's Guide to the Science of Natural Medicine," which Viking will publish on Aug. 6.