Stephen Ornes

Religious fasts offer opportunities for reflection, penitence and good data about human dietary needs.

Unlike laboratory rats, humans can’t be easily coerced into a new diet. Nutrition studies have had to grapple with that fact from the very start, which is why some of the earliest research was conducted in prisons, where Victorian researchers could control meals and see which ones were most likely to cause malnutrition or scurvy. Those methods hardly square with the ethics of modern research, which leaves investigators with the problem of where to find large populations that willingly undergo a dietary switch-up.

One avenue: Looking at religious fasts. Billions of people across the globe participate in observances of Christian Lent, which began this year on February 26 (March 2 for Orthodox Christians), or Islamic Ramadan, which starts April 23. For many practitioners, the season means reducing calories and skipping meat, among other practices. Others skip meals, or only eat during certain hours, a topic increasingly of interest at a time when “intermittent fasting” has become popular as a way to control weight.

One of the earliest religious diets under investigation has been that of the Seventh-Day Adventists, which recommends practitioners eat two meals per day and follow a plant-based diet year-round. Researchers have studied more than 100,000 Seventh-Day Adventists over the last six decades, and found that, on average, they live longer than non-Adventists of comparable demographics in the United States and have a lower risk of cancer. A number of follow-up studies are trying to tease out what factors may result in the increased longevity.