Key Takeaways
32% of Americans actively try to consume probiotics. (1)
Probiotic strains like Lactobacillus and Bifidobacterium are commonly used for weight loss. (2)
A recent study showed that 40% of people using probiotic supplements for 9 months saw a clinically relevant decrease in body weight without limiting their diet. (2)
Studies suggest that it generally takes 12 weeks of using probiotics for weight loss to see positive results. (2)
Doses of 1 million CFUs have been correlated with decreased fat, BMI, and waist circumference, with those potential impacts increased at higher doses. (2)
Although the results of weight loss from probiotics have been studied, further research is still needed to fully prove and understand this connection.
Foods high in probiotics include kefir, yogurt, sauerkraut, and other fermented foods.
If you’re a fitness enthusiast, you’ve probably heard people stress the importance of probiotics for gut health. These “good bacteria” that contribute to your gut bacteria overall have been getting a lot of attention for a few years now, with new research and supplements coming out almost daily. Probiotic supplements contain a variety of beneficial microbes credited with improving immunity, digestion, and even mental health.
Credit: fizkes / Shutterstock
In recent years, probiotics have also been promoted as a way to enhance weight loss efforts. As with any supplement, though, there’s a chance that the science is grossly exaggerated when marketing and social media get involved. So, can probiotics actually help with weight loss, or is this another case of science becoming science fiction?
What Are Probiotics?
Despite the widespread use of the word ‘probiotics’ to describe supplements, foods, drinks, and even dirt, there’s actually a specific definition. These products might contain microbes, but not all microbes are probiotic; they need to meet a few criteria to earn that label.
First, probiotics are live microorganisms. Second, they need to be ingested in adequate amounts. What’s an adequate amount? The answer to that question leads us to our third requirement: they need to provide a benefit to the host, which means they need to be backed up by research. So, “an adequate amount” is determined by however much necessary to replicate the results shown in those studies. (3)
Probiotic supplements contain specific amounts of certain bacteria or fungi that have already been studied for their effectiveness. Probiotics are sometimes combined with prebiotics, or carbohydrates that they prefer to use for energy, to create synbiotics. (3)(4)
[Read More: The Side Effects of Probiotics for Strength Athletes to Look Out For]
It’s worth noting that the effects of probiotics are strain-specific; in other words, there’s no one-size-fits-all probiotic.
You need to pick the right microbe for the job, whether you’re focused on your immune system, digestive health, blood pressure, or belly fat. (5)
What About Probiotic Foods?
Microbes have been used in food production for thousands of years because they can ferment carbohydrates to create alcohol, make bread rise, and extend the shelf-life of meat and dairy.
However, despite what you might hear on social media, foods and beverages that contain microbes aren’t automatically probiotic foods. If that were the case, beer and wine would be considered probiotic drinks, and you’d be eating your microbe-rich spoiled food instead of tossing it out. (Please don’t do this!)
[Read More: The Best Fruit and Vegetable Supplements for Taste, Probiotics, Fiber, and More]
In fact, at the moment, fermented dairy is the only food that meets probiotic criteria because it provides live microbes in adequate amounts to confer a documented benefit. While other fermented foods — like kimchi, kombucha, or natto — contain microbes, they don’t fit the definition of a probiotic (though some could still provide health benefits we haven’t discovered yet.) (6)
How Do Probiotics Work?
While it’s still unclear exactly how probiotics work — and there’s likely more than one mechanism — they seem to directly and indirectly influence both your gut microbiome (your gut microbiota and their genetic potential) and your body’s cells and tissues.
They probably interact with your gut microbiome as they pass through, rather than moving into the place permanently. They could outcompete potential pathogens (microbes that can cause disease in the right conditions) or engage in some cooperative behavior with the beneficial microbes native to your gut. (3)(4)(7)(8)
[Read More: How to Improve Your Gut Health — Evidence-Based Guidance for a Strong Stomach]
They could also interact directly with your intestinal and immune cells and communicate with your organs through indirect pathways via postbiotics, or metabolic products that happen to be beneficial to humans. (3)(4)(7)(8)
In terms of how these probiotics may help with weight loss, some research suggests that certain strains may reduce cell permeability in your intestines, leading to less inflammation. (2)
Do Probiotics Help With Weight Loss?
With so many potential pathways by which to influence human biology, it makes sense that probiotics would be targeted for research on such a popular topic as weight management.
[Read More: Can Your Gut Health Impact Weight Loss?]
Research does indicate that probiotic supplements are more effective than a placebo. Still, there are other factors to consider on your wellness journey.
How Could Probiotics Help With Weight Loss?
To understand how probiotics could help with weight loss, it’s important to understand the connection between the gut microbiome and body weight.
Discovering the Microbiome-Bodyweight Connection
Early studies in rodents suggested that there was a strong, potentially causative effect of the gut microbiome on body weight, body fat, and weight gain. Researchers used fecal microbiota transplants to colonize microbe-free mice with microbes from mice that were genetically modified to develop obesity, and the recipients also developed obesity. They were able to replicate this using fecal transplants from people with obesity, making this a compelling line of research. (9)(10)
In addition to studies like this, observational studies reported differences in the gut microbiomes of people with and without obesity. Not only were the communities of microbes different, but their genetic potential and activity differed, too.
[Read More: A Healthier Gut Could Mean More Muscular Strength]
It appeared that people with obesity had lower levels of diversity and genetic potential in their microbiomes, and the ratios of microbes were different. The gut microbiome became an overnight sensation as a potential target for weight management. (9)(10)
Human Studies Are Less Compelling That Rodent Studies
Unlike the rodent studies, however, human fecal transplants didn’t result in any spectacular outcomes. Unsurprisingly, a human with a fully developed gut microbiome doesn’t respond like a microbe-free mouse living in a sterile environment. (9)
Some postbiotics can affect areas of the brain linked to appetite and hunger, though the effect isn’t as pronounced in humans compared to rodents. Gut microbes can convert indigestible dietary carbohydrates to absorbable short-chain fatty acids, essentially liberating more energy from the diet for their human hosts. These fatty acids can bind to receptors on fat and muscle tissue, affecting pathways that regulate insulin sensitivity and fat breakdown. So, there’s potential for certain probiotic strains to have these effects, too. (3)(4)(7)(8)(11)
Which Probiotics Actually Help With Weight Loss?
Based on the findings of several meta-analyses over the last five years, probiotic supplements are consistently helpful with weight loss compared to placebo when you look at the statistics. When you consider the real-world results, though, it’s unclear whether they’re worth the money for most people.
If you want to give it a try, though, Lactobacillus and Bifiobacterium strains are the ones most commonly associated with weight loss.
Who Do Probiotics Help?
Studies have included a wide range of people: infants, adolescents, adults, and older adults, including people with and without obesity, gestational diabetes, or polycystic ovarian syndrome (PCOS). However, the majority of research has focused on adults with overweight or obesity.
Credit: Akarawut / Shutterstock
[Read More: The Best Probiotic Supplements for Women for Vaginal Health, Prebiotics, And More]
Probiotics are more effective in people with overweight, obesity, or cardiometabolic disease, so if you’re already considered metabolically healthy, you probably won’t see as much of a benefit. They don’t seem to have much of an effect in very young populations or during pregnancy. (3)(4)(7)(8)
How Much Do Probiotics Help?
Most meta-analyses reported that probiotics led to greater reductions in body weight, body mass index (BMI), waist circumference, and body fat mass compared to placebo, but the statistical significance doesn’t quite translate to a physically impactful change.
On average, participants lost anywhere from no extra body weight up to about one kilogram (about two pounds), which was also the case for fat percentage. Changes in BMI were similarly small, and waist circumference changed by about one centimeter. (3)(4)(7)(8)
[Read More: The Best Probiotics for Men]
Which Types of Probiotics Might Help, and How Much Should I Take?
If you do want to try a probiotic based on current research, expect to supplement for at least 12 weeks, but at this point, research doesn’t support a specific dosage. The hundreds of studies analyzed used anywhere from 104 to 1.35×1015 colony-forming units (CFUs), but in general, it seems that larger doses for longer durations might be more effective. (3)(4)(7)(8)
If you’re wondering which strains of probiotics are most effective, the recommendations are slightly more specific. (7) Keep an eye out for these species and strains, which have shown the most promise so far:
Lactobacillus casei Shirota
Lactobacillus gasseri BNR17
Lactobacillus rhamnosus
Lactobacillus plantarum
Bifidobacterium infantis
Bifidobacterium longum
Bifidobacterium breve B3
New microbes are being discovered all the time, so the bacterial names may change, and the list may grow as more research emerges.
Risks of Probiotics for Weight Loss
Like other dietary supplements, perhaps the most benign risk of using a probiotic is that it won’t do anything except make your wallet a little lighter. In most cases, the only adverse effect people report is gastrointestinal distress like gas, bloating, or changes in bowel habits.
However, probiotic supplementation can pose a risk to people taking certain prescription medications — like oral chemotherapy drugs or medicines used to treat Parkinson’s disease — as they can affect drug metabolism and efficacy. (12)
Frequently Asked Questions
What probiotic is best for weight loss?
Due to the variability in study design, it’s impossible to recommend a specific probiotic dose or the most effective strain(s), but some strains of Lactobacilli and Bifidobacteria show promise, and it seems that higher doses for at least 12 weeks are more likely to have some effect.
Will taking probiotics help you lose weight?
Technically, yes, they could help you lose weight. On average, though, people only lost about one kilogram (roughly two pounds) and the effects were only seen after three or four months of supplementation. Based on these results, you might be able to expect a loss of 250 to 300 grams (or ¼ pound) per month.
How long does it take for probiotics to work for weight loss?
Some studies reported results after just a week, but the majority of the evidence points to durations of at least three months to see significant results.
Are probiotics better than prebiotics for weight loss?
Prebiotic supplements exist, but you can obtain plenty of prebiotics from your food since fruits, veggies, whole grains, nuts, and beans all provide these types of carbohydrates. If they’re consumed in amounts that lead to a calorie deficit — which is necessary for weight loss, regardless of dietary pattern — these foods can help to support weight loss efforts. The prebiotics in these foods fuel your beneficial gut microbes, and they’re also nutrient-dense, filling, and unlikely to cause side effects or drug interactions. (3)
Probiotics, on the other hand, don’t have much of an effect and could pose a risk to some people, so they probably aren’t the superior choice compared to prebiotics.
Editor’s Note: The content on BarBend is meant to be informative in nature, but it should not be taken as medical advice. When starting a new training regimen and/or diet, it is always a good idea to consult with a trusted medical professional. We are not a medical resource. The opinions and articles on this site are not intended for use as diagnosis, prevention, and/or treatment of health problems. They are not substitutes for consulting a qualified medical professional.
References
Food Insight. 2021 Food & Health Survey. Retrieved from https://foodinsight.org/2021-food-health-survey/
Álvarez-Arraño V, Martín-Peláez S. Effects of Probiotics and Synbiotics on Weight Loss in Subjects with Overweight or Obesity: A Systematic Review. Nutrients. 2021 Oct 17;13(10):3627.
Rasaei, N., Heidari, M., Esmaeili, F., Khosravi, S., Baeeri, M., Tabatabaei-Malazy, O., & Emamgholipour, S. (2024). The effects of prebiotic, probiotic or synbiotic supplementation on overweight/obesity indicators: an umbrella review of the trials’ meta-analyses. Frontiers in endocrinology, 15, 1277921.
Saadati, S., Naseri, K., Asbaghi, O., Yousefi, M., Golalipour, E., & de Courten, B. (2024). Beneficial effects of the probiotics and synbiotics supplementation on anthropometric indices and body composition in adults: A systematic review and meta-analysis. Obesity reviews : an official journal of the International Association for the Study of Obesity, 25(3), e13667.
McFarland, L. V., Karakan, T., & Karatas, A. (2021). Strain-specific and outcome-specific efficacy of probiotics for the treatment of irritable bowel syndrome: A systematic review and meta-analysis. EClinicalMedicine, 41, 101154. Dimidi, E., Cox, S. R., Rossi, M., & Whelan, K. (2019). Fermented Foods: Definitions and Characteristics, Impact on the Gut Microbiota and Effects on Gastrointestinal Health and Disease. Nutrients, 11(8), 1806.
Perna, S., Ilyas, Z., Giacosa, A., Gasparri, C., Peroni, G., Faliva, M. A., Rigon, C., Naso, M., Riva, A., Petrangolini, G., A Redha, A., & Rondanelli, M. (2021). Is Probiotic Supplementation Useful for the Management of Body Weight and Other Anthropometric Measures in Adults Affected by Overweight and Obesity with Metabolic Related Diseases? A Systematic Review and Meta-Analysis. Nutrients, 13(2), 666.
Tabrizi, R., Ostadmohammadi, V., Akbari, M., Lankarani, K. B., Vakili, S., Peymani, P., Karamali, M., Kolahdooz, F., & Asemi, Z. (2022). The Effects of Probiotic Supplementation on Clinical Symptom, Weight Loss, Glycemic Control, Lipid and Hormonal Profiles, Biomarkers of Inflammation, and Oxidative Stress in Women with Polycystic Ovary Syndrome: a Systematic Review and Meta-analysis of Randomized Controlled Trials. Probiotics and antimicrobial proteins, 14(1), 1–14.
Pinart, M., Dötsch, A., Schlicht, K., Laudes, M., Bouwman, J., Forslund, S. K., Pischon, T., & Nimptsch, K. (2021). Gut Microbiome Composition in Obese and Non-Obese Persons: A Systematic Review and Meta-Analysis. Nutrients, 14(1), 12.
Gong, J., Shen, Y., Zhang, H., Cao, M., Guo, M., He, J., Zhang, B., & Xiao, C. (2022). Gut Microbiota Characteristics of People with Obesity by Meta-Analysis of Existing Datasets. Nutrients, 14(14), 2993.
Lahtinen, P., Juuti, A., Luostarinen, M., Niskanen, L., Liukkonen, T., Tillonen, J., Kössi, J., Ilvesmäki, V., Viljakka, M., Satokari, R., & Arkkila, P. (2022). Effectiveness of Fecal Microbiota Transplantation for Weight Loss in Patients With Obesity Undergoing Bariatric Surgery: A Randomized Clinical Trial. JAMA network open, 5(12), e2247226.
Corbin, K. D., Carnero, E. A., Dirks, B., Igudesman, D., Yi, F., Marcus, A., Davis, T. L., Pratley, R. E., Rittmann, B. E., Krajmalnik-Brown, R., & Smith, S. R. (2023). Host-diet-gut microbiome interactions influence human energy balance: a randomized clinical trial. Nature communications, 14(1), 3161.
Purdel, C., Ungurianu, A., Adam-Dima, I., & Margină, D. (2023). Exploring the potential impact of probiotic use on drug metabolism and efficacy. Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie, 161, 114468.
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