Our guts are home to trillions of bacteria — both good and bad. Research in recent years has proven that the health of our gut microbiomes affects much more than just digestion, and that fasting for short periods may help to regulate these bacteria. 

Just like our bodies have a 24-hour circadian rhythm that dictates our sleeping and waking times, the gut microbiome also responds to this rhythm. The composition and function of our gut bacteria fluctuate throughout the day, which is a leading reason why intermittent fasting — withholding food for a period of each day, typically in a 14-16 hour window — benefits the gut. 

Helps Metabolic Control 

Circadian rhythms can dictate how nutrients are processed and absorbed, including carbohydrates like glucose. Insulin — the hormone that shuttles glucose from the blood into cells —  is most effective in the morning and afternoon. At night, hormones like melatonin interfere with insulin, leading to higher blood glucose when we eat carbohydrates. Therefore, not eating during the evening and overnight period can benefit blood sugar control. 

Boosts Immune System

Fasting can lead to the regeneration of certain immune cells that are present in the gut. When a period of fasting begins, the body will start to break down white blood cells called lymphocytes that fight infection. This then leads to the growth of healthy, new lymphocytes that strengthen the immune system. 

Reduces Inflammation

Studies of intermittent fasting have found that forgoing food for some time reduces the release of pro-inflammatory cells called monocytes. During fasting, these cells essentially go into a “sleep mode” that is less inflammatory. As high levels of monocytes are detrimental to gastrointestinal health, intermittent fasting may be one way to reduce inflammation and support healthier guts. 

The Bottom Line:

Intermittent fasting can benefit gut health, including supporting healthier microbiomes, metabolic control, immune system functioning, and reduced inflammation. However, you’ll want to be sure you are not undereating calories or fiber, as this can be detrimental to gut health.