Fasting May Benefit Our Gut Health

There is a lot of talk about intermittent fasting.  While the claims of health benefits to intermittent fasting span a wide range – from slowing aging and disease processes to improving brain health, there are many discussions that center around the efficacy and potential risks of fasting. Here, we hope to approach one of the benefits to intermittent fasting through a scientific lens.

Fasting is defined as abstinence from calorie intake over an extended period of time. With a focus on the intestinal microbiome, emerging studies that primarily use animal models have underscored the possible advantages of fasting for our gut health, which include the reduction of inflammation within the intestines, a boost in the presence of intestinal stem cells, and the proliferation of gut bacteria.

Recently, a controlled clinical trial of 51 participants was designed to investigate the impact of periodic routine fasting on gut microbiota composition and longevity-related genes. Periodic routine fasting is a type of fasting that involves longer time intervals between fasts; for example, a 48-hour fast once per month.

In the study, participants were either assigned to a fasting group or a non-fasting control group. Samples were first collected from all participants. Then, the fasting group underwent five consecutive days of fasting, which involved a daily energy intake of 250 kcal maximum. After five days, samples were collected again.

After analyzing the results, researchers reported that the fasting group showed changes in intestinal microbiota: 1. An expansion of diversity at the phylum and species levels; 2. differences in signaling proteins for metabolism; and 3. An increase in ketone bodies.

To dive in further: after the fasting treatment, researchers noted a significant increase for Christensenella, a longevity-relevant gut microbiota which is strongly correlated with healthy levels of triglycerides and good cholesterol. In addition, Christensenella has previously been associated with the gut microbial make-up of populations who live to be over 100 years old.

The researchers also noted that fasting significantly increased blood levels of SIRT1, SIRT3, FoxO1, and miRlet7b-5pis proteins. SIRT proteins are signaling proteins that are involved in metabolic function and cellular health, including DNA repair, cell survival, and stress resistance. Animal studies have even proposed that SIRT1 is associated with longevity, promoting mitochondrial biogenesis and functioning, and that SIRT3 can regulate mitochondrial metabolism and homeostasis.

Lastly, researchers found significantly higher levels of beta-hydroxybutyrate, a ketone body that is associated with the reduction of age-related neurological impairments, in the blood samples of the fasting group.

All in all, the results from this clinical study suggest that periodic fasting can impact on the composition of the intestinal microbiota, creating more diversity at the species level, while also increasing the expression of microbiota, genes, and metabolites that are relevant to aging and longevity.

By: Helena Zhang, BS & Sean Spencer, MD


  1. Five Days Periodic Fasting Elevates Levels of Longevity Related Christensenella and Sirtuin Expression in Humans
  2. Effects of Intermittent Fasting on Health, Aging, and Disease