table of contents
If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.
Your body has about 40 trillion bacteria—most of which can be found in your gut (Sender, 2016). Together, this collection of gut bacteria is known as the microbiome, now considered a key contributor to overall health. Recent research even suggests your gut microbiome can influence your ability to lose weight (Diener, 2021).
So what’s the relationship between gut health and weight loss? Let’s find out.
What is the gut microbiome?
The human body is home to millions of microorganisms, tiny living things found all around us and too small to be seen by the naked eye. The most common types are bacteria, viruses, and fungi.
Trillions of these microbes live on our skin and inside our intestines. Most of the microbes in our intestines are located in a “pocket” of the large intestine called the cecum, and these are the organisms that make up the gut microbiome.
The microorganisms found in your gut microbiome can play an essential role in your health, though some can also cause disease. The microbes that make up the gut microbiome may weigh as much as 2–5 pounds (John, 2018).
How does gut health influence weight?
Most of the bacteria found in your gut microbiome positively affect your health and help contribute to your body’s natural processes. But when one of these colonies of bacteria gets out of whack, it can lead to something called gut dysbiosis, which is an imbalance of healthy and unhealthy microbes. Dysbiosis has been shown to contribute to weight gain (Patterson, 2016).
However, research also shows that specific “good” microbes in the gut may help you lose weight. In one study of dieters, researchers compared people who had lost weight to those whose weight had remained the same. The main difference was the types of gut microbes the two groups had. The people who lost more weight not only had more beneficial enzymes in their guts, but they also had certain bacterial colonies that may support weight loss (Diener, 2021).
Gut flora and weight loss: what’s the connection?
Your gut bacteria can affect how your food is digested, how fat is stored, and whether you feel hungry or full—all of which can affect your ability to lose weight. Let’s dig into each of these factors.
Because the bacteria that line your gut come into constant contact with the food you eat, they affect how the body absorbs those nutrients. The human gut microbiome is a critical component of digestion, breaking down complex carbohydrates, proteins, and to a lesser extent, fats that reach the lower gastrointestinal tract (Oliphant, 2019). For example, gut microbes—digestive enzymes—break down dietary fiber. By digesting fiber, these gut bacteria produce several chemicals that may promote weight loss (Koh, 2016).
Inflammation happens when your body activates your immune system to fight infection. Your gut bacteria play an essential role in inflammation. Some bacteria found in the gut produce chemicals that cause inflammation when they pass into the blood (Al Bander, 2020). These elevated inflammatory chemicals can contribute to weight gain (Saltiel, 2017).
On the other hand, certain species of gut bacteria can lower inflammation, preventing weight gain. In a recent study, mice who were fed prebiotic fibers to help increase Bifidobacteria bacteria in the gut showed a decrease in weight gain (Cani, 2007).
Hunger and fullness
Your body produces certain hormones—such as leptin, ghrelin, glucagon-like peptide 1 (GLP-1), and others—which affect your appetite. The different bacteria present in your gut can affect how much of each of these hormones is produced, which then affects how hungry or full you feel (Fetissov, 2017). For example, one study showed that people who took propionate—a short-chain fatty acid produced when certain species of gut bacteria break down fiber—had levels of these appetite-affecting hormones that led to reduced food intake and reduced weight gain (Chambers, 2015).
Best foods for gut health and weight loss
There are many different foods that are good for supporting healthy gut bacteria. These include:
- Whole grains—These foods are high in fiber. When digested by healthy gut bacteria, they may help with weight loss.
- Probiotic foods—Probiotic foods like kimchi, kombucha, and kefir contain living microorganisms like the health-promoting microbes found in your gut and can minimize disease-causing bacteria in the gut.
- Polyphenol-rich foods—These include dark chocolate, green tea, and red wine. The presence of these foods in the gut promotes the growth of good bacteria.
- Fruits and vegetables—Gut bacteria diversity is linked to a healthy weight—and eating a variety of fruits and vegetables can give you that diversity.
- Nuts—Nuts also contain a lot of fiber, which promotes the growth of healthy bacteria.
You may not have realized just how important gut health is to losing or maintaining a healthy weight. But by eating the right foods for a healthy microbiome, you can not only improve your chances of losing weight—but you can improve your overall health as well.
- Al Bander, Z., Nitert, M. D., Mousa, A., & Naderpoor, N. (2020). The gut microbiota and inflammation: An overview. International Journal of Environmental Research and Public Health, 17(20), 7618. doi:10.3390/ijerph17207618. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7589951/
- Cani, P. D., Neyrinck, A. M., Fava, F., et al. (2007). Selective increases of bifidobacteria in gut microflora improve high-fat-diet-induced diabetes in mice through a mechanism associated with endotoxaemia. Diabetologia, 50(11), 2374–2383. doi:10.1007/s00125-007-0791-0. Retrieved from https://pubmed.ncbi.nlm.nih.gov/17823788/
- Chambers, E. S., Viardot, A., Psichas, A., et al. (2015). Effects of targeted delivery of propionate to the human colon on appetite regulation, body weight maintenance and adiposity in overweight adults. Gut, 64(11), 1744–1754. doi:10.1136/gutjnl-2014-307913. Retrieved from https://pubmed.ncbi.nlm.nih.gov/25500202/
- Diener, C., Qin, S., Zhou, Y., et al. (2021). Baseline gut metagenomic functional gene signature associated with variable weight loss responses following a healthy lifestyle Intervention in humans. mSystems, 6(5), e0096421. doi:10.1128/mSystems.00964-21. Retrieved from https://pubmed.ncbi.nlm.nih.gov/34519531/
- Fetissov, S. O. (2017). Role of the gut microbiota in host appetite control: bacterial growth to animal feeding behaviour. Endocrinology, 13(1), 11–25. doi:10.1038/nrendo.2016.150. Retrieved from https://pubmed.ncbi.nlm.nih.gov/27616451/
- John, G. K., Wang, L., Nanavati, J., et al. (2018). Dietary alteration of the gut microbiome and its impact on weight and fat mass: a systematic review and meta-analysis. Genes, 9(3), 167. doi:10.3390/genes9030167. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5867888/
- Koh, A., De Vadder, F., Kovatcheva-Datchary, P., et al. (2016). From dietary fiber to host physiology: short-chain fatty acids as key bacterial metabolites. Cell, 165(6), 1332–1345. doi:10.1016/j.cell.2016.05.041. Retrieved from https://pubmed.ncbi.nlm.nih.gov/27259147/
- Oliphant, K., Allen-Vercoe, E. (2019). Macronutrient metabolism by the human gut microbiome: major fermentation by-products and their impact on host health. Microbiome 7, 91. doi:10.1186/s40168-019-0704-8. Retrieved from https://microbiomejournal.biomedcentral.com/articles/10.1186/s40168-019-0704-8#citeas
- Patterson, E., Ryan, P. M., Cryan, J. F., et al. (2016). Gut microbiota, obesity and diabetes. Postgraduate Medical Journal, 92(1087), 286–300. doi:10.1136/postgradmedj-2015-133285. Retrieved from https://pubmed.ncbi.nlm.nih.gov/26912499/
- Saltiel, A. R. & Olefsky, J. M. (2017). Inflammatory mechanisms linking obesity and metabolic disease. The Journal of Clinical Investigation, 127(1), 1–4. doi:10.1172/JCI92035. Retrieved from https://pubmed.ncbi.nlm.nih.gov/28045402/
- Sender, R., Fuchs, S., & Milo, R. (2016). Revised estimates for the number of human and bacteria cells in the body. PLoS Biology, 14(8), e1002533. doi:10.1371/journal.pbio.1002533. Retreived from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4991899/
Dr. Steve Silvestro is a board-certified pediatrician and Senior Manager, Medical Content & Education at Ro.