Give that Gut a Break: Intermittent Fasting and Healthy Gut Bacteria

Written by Mildred Monsivais and Edited by Mehr Kaur Bawa

Starvation is often seen as detrimental to health, and in some cases can even be lethal. Prolonged starvation can have numerous physical and physiological effects on the body. But can not consuming food for a part of the day actually benefit your health? Intermittent fasting, also known as intermittent energy restriction, is a cycle of fasting and eating within a certain time frame that has shown to benefit overall health [1].

Our body contains microbes, tiny microorganisms such as bacteria, that play an important part in digesting food and producing chemicals. In particular, our gut contains 100 trillion living bacteria that work toward making vitamins and breaking down food and toxins [2]. Intermittent fasting allows the gut to take a break from all this digesting and breaking down of food. Reducing the energy-intensive task of digestion has been shown to decrease the amount of postprandial endotoxemia, a metabolic risk factor that increases the risk of Metabolic Syndromes, conditions that increase the risk of heart disease, stroke and type 2 diabetes [2].

Throughout most of human civilization, humans ate only one or two meals a day since food was a limited resource and our ancestors 12,000 years ago had to hunt and gather food to survive [3]. However, over time, increased food availability resulted in substantial changes in eating habits. Increased food availability lead to increased food consumption throughout the day, making it harder to regenerate microbe diversity in the gut. So why don’t we go back to the way our ancestors ate and implement intermittent fasting to ensure better regeneration of gut microbes?

Intermittent fasting benefits our gut microbes’ circadian rhythm, the cyclical pattern in which certain gut bacteria are active at different times of the day. The circadian rhythm controls our body’s energy, including sleep and appetite. There are different types of gut bacteria active at night compared to during the day. For example, Postprandial Endotoxemia is a bacteria that breaks down carbohydrates and is sensitive to the sleep hormone melatonin [4]. Eating at night disrupts the function of gut bacteria rhythm just as jet lag disrupts the sleep cycle.  As a result, a common form of intermittent fasting, the 16:8 diet, consists of an 8-hour window frame of eating and 16 hours of restricted food consumption so that the gut bacteria rhythm can be better controlled and maintained.

Not only is fasting beneficial to your circadian rhythm, but it can also produce beneficial metabolic changes such as lower blood pressure, weight, fat mass, blood glucose and low-density lipoprotein (LDL) cholesterol [5]. A study done at the University of Alabama found that changing the time at which meals are eaten can benefit metabolism. In this study, obese men were split into two groups testing the 2 different forms of intermittent fasting [6]. The first group had a time frame of eating between 7 am-3 pm and the second group had a time frame between 7 am-7 pm. The results showed that after 5 weeks of fasting, the first group had lower insulin, blood pressure and appetite levels– indicating how intermittent fasting can lower factors that contribute to Metabolic Syndromes [6]. 

Intermittent fasting can be safe and beneficial if done correctly. The time break in food consumption allows gut bacteria to rejuvenate and regrow. Furthermore, the lower levels of blood pressure, insulin, and appetite associated with intermittent fasting can result in a decreased risk of major diseases of concern such as heart attack, stroke, and diabetes [2]. With such positive benefits, perhaps intermittent fasting is something to consider and try. 

References:

1. “Diet Review: Intermittent Fasting for Weight Loss.” The Nutrition Source, Harvard School of Public Health, 2019, www.hsph.harvard.edu/nutritionsource/healthy-weight/diet-reviews/intermittent-fasting/.
2. Hsiao, W.W.L., Metz, C., Singh, D.P., Roth, J. (2008). The microbes of the intestine: an introduction to their metabolic and signaling capabilities. Endocrinology and metabolism clinics of North America, 37: 857–871.
3. Pattillo, Alexandra. “Is Intermittent Fasting ‘Natural’? History Experts React to the Controversy.” Inverse, 26 July 2019, www.inverse.com/article/57835-intermittent-fasting-evolution.
4. Paulose, J.K., Cassone, V.M. (2016). The Melatonin-Sensitive Circadian Clock of the Enteric Bacterium Enterobacter Aerogenes. Gut Microbes, 7: 424–427.
5. Reinagel, Monica. “Does Intermittent Fasting Work?” Scientific American,
   Springer Nature, 2 Feb. 2019,
   www.scientificamerican.com/article/does-intermittent-fasting-work/. 
6. Tello, Monique. “Intermittent fasting: Surprising update.” Harvard Health Publishing, Harvard Medical School, 29 June 2018,
   www.health.harvard.edu/blog/intermittent-fasting-surprising-update-2018062914156.