Fasting, and especially intermittent fasting, is totally a topic that is either hit or miss in the wellness space. You’re either for it or against it. Although they often get quite a bad rap for leaning more towards a fad diet trend, there are actually some pretty surprising benefits that have nothing to do with losing weight fast.
Our gut is host to what is often referred to as our microbiome, a large population of commensal bacteria and microbes that play a major role in maintaining not only gut health but our overall health. Essentially, eating feeds our gut microbes – some foods better than others – and like us they also benefit from a bit of a break for digestion, health and sleep. Which is where fasting comes in.
The benefits of which fasting has on our gut microbes provides health effects that research is really only just discovering. Read on for discovering these scientific findings for yourself.
The Brain-Gut-Microbiome
Research over the last decade has increased our understanding of the brain-gut-microbiome interaction. These interactions integrate the central nervous system, gastrointestinal and immune systems which are bidirectional and is referred to as a separate organ – the gut-brain axis. These interactions are remarkable in that they are associated in the development of prevalent gastrointestinal disturbances such as IBS but also in the development of neurological disorders such as Parkinson’s disease. The Greek physician, Hippocrates the father of modern medicine, proclaimed that ‘All disease begins in the gut’, and he wasn’t kidding.
The pathways of which the gut and brain communicate includes nerves, such as the vagal nerve running from the brain and innervating the gastrointestinal system, signalling of the immune system and of course metabolites produced by our microbiome such as amino acids and short-chain fatty acids. So, if one side of the conversation is impaired it is highly likely the other will be affected and vice versa.
A large portion of gut health is governed by having this balance of beneficial and not-so-beneficial bacteria - pathogenic. In circumstances where there is an imbalance in the quality and quantity of beneficial bacteria – known as dysbiosis – this can increase risk of complications. Whether these are local to the gut such as SIBO (small intestinal bacteria overgrowth), inflammation and abdominal discomfort, and/or among neurodevelopment such as anxiety and depressive behaviour, taste preference and feeding behaviours.
Intermittent Fasting
Gut microbes play a role in the breakdown and absorption of nutrients and energy we obtain from food. Our intestinal bacteria is definitely impacted greatly by what we eat as it stimulates the growth of good bacteria through whatever nutrients we have ingested. But is also impacted by the periods between eating. Intermittent fasting involves fasting from 12-48 hours – although 12 being the most common – for a prolonged period of time. This could look like finishing your dinner or dessert by 6:30pm and not having your breakfast until 6:30am the following morning, day in day out. Which in a lot of people’s case is what they naturally do anyway!
By giving our microbes a break, whether that’s 12 hours or less, studies have shown that intermittent fasting can lead to the beneficial modification and increased diversity of the microbiome. Increased amounts of beneficial bacteria during intermittent fasting, such as Lachnospiraecae, promote healthful longevity and metabolic effects through the production of butyrate – a beneficial short chain fatty acid that is preferred for protecting the intestinal barrier and exerting anti-inflammatory properties.
The Link to Disease
Some studies actually suggest that time-restricted feeding patterns, such as between 6-8 hours, are favourable in the management of various conditions that affect our health and overall well-being. This suggestion stems from the idea that humans evolved when food sources were scarce and eating depended on availability. And due to the present-day abundance and access to high-calorie food this has led to the susceptibility of chronic disease such as obesity, type 2 diabetes, hypertension and hyperlipidaemia.
In the development of some chronic diseases research has shown an over-abundance of pathogenic bacteria often due to being over-fed, and ingestion of the wrong foods – processed or refined sugar foods. When there is an abundance of pathogenic bacteria, such as E. coli, levels of fermentation and inflammation are higher due to a lower abundance of good bacteria, such as Bifidobacterium. This is commonly seen in IBS where inflammation is occurring due to dysbiosis.
For conditions that contain inflammation of the bowel - IBD and IBS - intermittent fasting shows beneficial effects through food restriction. This shifts gut microbiome diversity in a positive direction to decrease feeding pathogenic bacteria - E. coli – and lowering inflammation. And, of course, when inflammation is reduced within the gut this reduces inflammation elsewhere. Which, in IBS, can prevent psychological symptoms like anxiety or OCD through regulation of the gut-brain-microbiome axis. Our bodies are just one big connected system!
And when we say fasting we don’t mean restrict intakes for ridiculously long periods of time because, quite frankly, that is not healthy. However, giving your microbiota a decent rest overnight may be beneficial for you if you do experience gastrointestinal symptoms like IBS or feelings of being overly full, which can involve a heck of a lot of abdominal discomfort. Our microbiomes do so much more work than we think.
Martin, C. R., Osadchiy, V., Kalani, A., & Mayer, E. A. (2018). The Brain-Gut-Microbiome Axis. Cellular and molecular gastroenterology and hepatology, 6(2), 133–148. https://doi.org/10.1016/j.jcmgh.2018.04.003
Larrick, J. W., Mendelsohn, A. R., & Larrick, J. W. (2021). Beneficial Gut Microbiome Remodeled During Intermittent Fasting in Humans. Rejuvenation research, 24(3), 234–237. https://doi.org/10.1089/rej.2021.0025
Rivière, A., Selak, M., Lantin, D., Leroy, F., & De Vuyst, L. (2016). Bifidobacteria and Butyrate-Producing Colon Bacteria: Importance and Strategies for Their Stimulation in the Human Gut. Frontiers in microbiology, 7, 979. https://doi.org/10.3389/fmicb.2016.00979
Cryan, J. F., O'Riordan, K. J., Cowan, C. S. M., Sandhu, K. V., Bastiaanssen, T. F. S., Boehme, M., Codagnone, M. G., Cussotto, S., Fulling, C., Golubeva, A. V., Guzzetta, K. E., Jaggar, M., Long-Smith, C. M., Lyte, J. M., Martin, J. A., Molinero-Perez, A., Moloney, G., Morelli, E., Morillas, E., O'Connor, R., … Dinan, T. G. (2019). The Microbiota-Gut-Brain Axis. Physiological reviews, 99(4), 1877–2013. https://doi.org/10.1152/physrev.00018.2018
Vijay, A., & Valdes, A. M. (2022). Role of the gut microbiome in chronic diseases: a narrative review. European journal of clinical nutrition, 76(4), 489–501. https://doi.org/10.1038/s41430-021-00991-6
Zhang, X., Zou, Q., Zhao, B., Zhang, J., Zhao, W., Li, Y., Liu, R., Liu, X., & Liu, Z. (2020). Effects of alternate-day fasting, time-restricted fasting and intermittent energy restriction DSS-induced on colitis and behavioral disorders. Redox biology, 32, 101535. https://doi.org/10.1016/j.redox.2020.101535
