There is some evidence that religious fasting practices can change the gut microbiome and gut physiology in ways that may improve markers of gut health, but findings are mixed and depend on the type, duration, and context of the fasting practice as well as the population studied.[2]
Essential context and supporting details
– Types of religious fasting and how they differ
– Religious fasting covers a range of patterns: Ramadan-style daily fasts from dawn to sunset, extended occasional fasts, and other culturally specific fast days or periods. These differ in daily fasting window, caloric intake when not fasting, and duration in days or weeks, which affects biological responses.[2]
– Microbiome changes observed
– Studies of intermittent or time-restricted eating, including Ramadan fasting, report shifts in gut microbial composition during fasting periods, such as changes in the relative abundance of certain bacterial groups linked to metabolism and inflammation.[2] These shifts are often transient and may return to baseline after fasting ends.[2]
– Effects on gut barrier function and inflammation
– Experimental and review sources describe mechanisms by which reduced meal frequency or short-term fasting can reduce gut inflammation and improve intestinal barrier function in animal models and some human studies, for example via increased production of mucin and short-chain fatty acids that support colon health and by lowering postprandial metabolic stress[1]. However, much of the mechanistic evidence comes from preclinical work or small human studies and cannot fully establish long-term benefits in diverse human populations[1].
– Clinical outcomes and human study limitations
– Human studies of religious fasting often show modest changes in body weight, appetite measures, and some metabolic markers over the fasting period, but they vary in size, methods, and controls, making it hard to generalize findings to long-term gut health outcomes.[2] Many studies are observational during Ramadan or other religious fasts, so confounding factors such as sleep changes, meal composition at night, and hydration make causal interpretation difficult[2].
– Safety and context
– Fasting can be safe for many healthy adults, but it may be harmful for people who are undernourished, have certain chronic illnesses, are pregnant, or take medications requiring regular food intake; clinical guidance and individualized assessment are recommended when people with health conditions consider fasting[1].
– What the evidence does and does not show
– The evidence supports that religious fasting can cause measurable short-term changes in the gut microbiome and gut-related physiology and can reduce some inflammatory signals in certain settings[1][2].
– The evidence is insufficient to claim consistent, durable improvements in overall gut health across populations because long-term randomized trials are limited, study designs are heterogeneous, and many mechanistic findings come from animal studies or small human cohorts[1][2].
Sources
https://www.youtube.com/watch?v=IQoQi-C-uzk
https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2025.1718105/full
