Intermittent fasting, a dietary practice in which individuals repeatedly, voluntarily, and heavily restrict food intake for approximately 16 to 24 hours, is a popular dietary intervention for weight loss and increased glucose tolerance. Some of the beneficial effects of intermittent fasting arise from its ability to modulate the gut microbiota, the community of microbes that live in the gastrointestinal tract. Findings of a recent report demonstrate the effect of intermittent fasting on microbiota structure and function in adults observing the Islamic faith-associated month of Ramadan.
There are many health benefits attributed to intermittent fasting with the American Heart Association claiming that intermittent fasting may produce weight loss, reduce insulin resistance, and lower the risk for cardiometabolic diseases; however, the mechanisms that drive these benefits in humans are unclear. Experiments in mouse models have suggested that intermittent fasting produces changes in circadian biology and remodeling of the gut microbiota, but further research in humans is needed.
The investigators recruited two cohorts of participants. The first cohort consisted of healthy young adult males (average age, 19 years) who expressed intention to fast during the month of Ramadan according to Islamic law, which dictates 30 days of fasting from dawn to sunset (approximately 16 hours in this study). These participants provided stool samples for microbiome analysis and blood for the measurement of metabolic makers before the start of Ramadan, 15 days into the month, and at the end of the month. The second cohort consisted of healthy middle-aged adults (average age, 40 years). Some participants in this cohort practiced Ramandan fasting and some did not. Participants in this cohort also provided stool samples for microbiome analysis and blood samples for the measurement of metabolic markers. The researchers collected this data at the beginning and end of the month of Ramadan and 30 days afterward.
The researchers found that microbiota diversity increased among participants practicing Ramadan-associated intermittent fasting compared to non-fasting participants. This diversity was specifically associated with increased abundance of the bacterial families Lachnospiraceae and Ruminococcaceae. Lachnospiraceae is capable of producing the short-chain fatty acid butyrate, which is a known promoter of metabolic health. Increased abundance of Lachnospiraceae was associated with beneficial changes in liver enzymes. Microbiota composition returned to normal 30 days following the end of Ramadan.
The authors concluded that intermittent fasting alters the composition of the gut microbiota. Specifically, fasting increased the abundance of the butyrate-producing Lachnospiraceae family, which may explain some of the beneficial physiological effects of intermittent fasting.
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