Probiotics and Weight Loss: The Link + Risks | Signos

Is there a connection between probiotics and weight loss? Possibly, but here’s why the answer isn’t black or white.

Numerous mason jars with probiotic-rich fermented foods, including pickles and vegetables.
by
Sabrina Tillman
— Signos
Health & Fitness Writer
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Reviewed by

Sabrina Tillman
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Updated by

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Science-based and reviewed

Published:
April 23, 2024
August 25, 2021
— Updated:
June 24, 2022

Table of Contents

What you weigh can be influenced by much more than what you eat and how much you move. 

Did you know you have a gut-brain connection where the bacteria in your gut can influence hormones that regulate appetite and satiety? Your gut and digestive system are often called your “second brain.” The microbes in your belly can signal to your brain that you’re satisfied, or they can whisper that you need a heaping order of nachos before your taco trio entree.

Your gut microbiota (the collection of microorganisms living in your gastrointestinal tract) may even influence how many calories you burn. Probiotics, the live bacteria or yeasts that live in your gut, are “good” bugs that work to keep you healthy, digest your food, metabolize vitamins, and, yes, possibly influence your weight.

But is there an actual connection between gut bacteria and weight loss? Possibly, but weight loss from taking probiotic supplements alone remains a pipe dream. That said, a healthy gut, along with lifestyle habits like a healthy diet, could influence weight, so adding probiotics in some instances may be supportive. Science hasn’t quite figured out all the details yet.

This article will dive into what we know about probiotics and weight loss and where the science may lead us in the future. 

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What Do Probiotics Help With?

Probiotics, live microorganisms found in yogurt, supplements, and fermented foods, are beneficial bacteria ingested to improve balance in your gut microbiome. Astonishingly, your gut hosts trillions of microorganisms from more than 500 different species, and many of these are essential for your overall health.

Probiotic supplements come in many different types (called probiotic strains), and each may play a different role in the body. These supplements are designed to match naturally occurring good bacteria in the gut so they can add to the existing healthy populations. Some common strains include yeasts like Saccharomyces boulardii or bacteria such as Lactobacillus acidophilus and Bifidobacterium animalis


The more we learn about probiotics and the body, the more we learn about how they may provide health benefits, including:

  • Influence your immune system and inflammatory response
  • Strengthen and maintain the lining of your mucosal intestinal barrier 
  • Lower blood sugar (glucose) levels and increase insulin sensitivity
  • Support and possibly prevent certain digestive health conditions like irritable bowel syndrome (IBS) or constipation
  • Ease allergy symptoms

Probiotic dosage is expressed in CFU or colony-forming units. The number of CFUs relates to the number of live strains in each dose; some probiotic pills contain millions of CFUs, and others have hundreds of billions.

Knowing the CFU dosage is necessary because when you take a probiotic supplement for a specific condition, you want to ensure the number of bacteria in your product is high enough to have an impact (called a therapeutic dose).

The strain type, product formula, quality, and dose you choose will depend on your purpose for taking it. For example, strains to help with antibiotic-associated diarrhea may differ from those for blood sugar or metabolic support. 

If you have any concerns, you can discuss dosage, duration, and strain with your doctor or healthcare practitioner before starting supplementation.

Do Probiotics Help You Lose Weight?

Scientific research remains mixed on whether probiotics can directly help with weight loss or weight management. Weight loss is a complex topic that includes diet, lifestyle, genetics, hormones, and more. Probiotics may play a role by supporting some of these factors. 

Let’s comb through some of the research highlights.

A meta-analysis of clinical trials from 2015 concluded that probiotics are not effective for weight loss or decreasing body mass index (BMI). On the other hand, a more recent systematic review and meta-analysis from 2021 found positive outcomes for probiotic supplementation for anthropometrics (body measurements), including BMI and hip and waist circumference (although body weight was not significant). A 2016 study found that supplementing with Bifidobacterium lactis supported healthy body fat mass.

Studies have also found that certain strains of the Lactobacillus family can help individuals lose weight. In one study, eating yogurt with Lactobacillus fermentum or Lactobacillus amylovorus reduced participants’ body fat by 3 to 4% over six weeks.21 Another study showed that women taking Lactobacillus rhamnosus supplements lost 50% more weight over three months compared to those women taking a placebo pill.22 

There is some indication that probiotics with more than one strain could help with body weight by impacting eating behaviors and hunger hormones, which could influence body weight and other body measurements like body mass index (BMI). Along with hunger hormones, probiotics (along with prebiotics) could affect neurotransmitters that impact cravings and food choices that can lead to weight gain. At the same time, a systematic review found that probiotics have minimal effects on appetite-related hormones for people who are overweight.

Why all the differences? A primary reason is that we are all so different and have different existing bacterial species in our guts. Some people may see benefits because they do have existing bacterial imbalances, while others may not see the same improvements. 

Studies do show that people with obesity have different gut microbiomes than leaner matched controls (even in twin studies), with an imbalance of critical species, and probiotic supplementation has been shown to positively influence the make-up of the microbiome to favor more beneficial bacteria, but whether this is enough to impact weight loss remains to be seen.

Probiotics for Weight Loss: What to Take


A bowl with yougurt with raspberries and blueberries

If you’re curious about adding probiotics to your weight loss routine, you can experiment to see if supplementing makes a difference. It’s always a good idea to consult with your doctor or healthcare provider, but few known side effects exist from probiotics (more on this below), so they are a relatively safe option for most people.

When choosing a high-quality probiotic for weight loss, there are a few things to consider. First, since we don’t know what strains are best for weight loss, the best probiotics are a multi-strain option that contains lactobacillus and bifidobacterium is a good place to start because these are some of the most well-researched. You also want to make sure the CFUs are listed on the ingredient list so you know you are getting a high enough dose to make an impact.

Not all probiotics need refrigeration, but if they do, you want to ensure the product has been stored properly. Finally, you want to ensure that the brand you purchase has a good reputation and that your product is free of contamination (and contains what the label says it does). Third-party verifications like NSF international or USP Dietary Supplement Verification help ensure the quality and potency of the product.

Probiotics for Weight Loss on a High-Fat Diet

If you’ve tried keto or a low-carb diet to lose weight, you may have read that some animal studies link a high-fat (and high animal protein) diet to changes in the gut microbiota that may encourage weight gain. One such study in rats suggested that a high-fat, high-calorie diet led to inflammation in the gut that impaired food intake regulation and possibly triggered excessive eating and obesity. While these aren’t studies on humans, some research suggests that high dietary fat may also impair the human microbiome.

But you don’t need to skip the olive oil or stop adding avocado to everything yet. A study (on humans) showed promise in triple viable probiotics supplementation for those on a high-fat diet—the probiotics expanded the species of beneficial gut bugs and reduced the bad ones (although it’s worth noting that the effect was even stronger when combined with a dietary intervention that reduced fat intake). 

Another study on young adult men without obesity found that supplementation with VSL#3, a multispecies probiotic containing strains like Lactobacillus plantarum and Bifidobacterium longum, provided protection against body weight and fat mass gain during a high-calorie, high-fat diet.

Don’t Come up Short on SCFAs: How to Hack Your Appetite

The gut microbiota plays a role in energy metabolism by producing short-chain fatty acids (SCFAs), made when your gut bugs break down fiber. Acetate, propionate, and butyrate are SCFAs that can impact inflammation, insulin sensitivity, blood sugar balance, and body weight—in many ways, including regulating satiety and reducing appetite.

For example, butyrate may activate the gut-brain axis to help reduce calorie intake and rev up fat burning to support a healthy weight. Studies also suggest that propionate can influence hunger and satiety, and acetate may have appetite-suppressing properties.

How can you reap the potential weight-impacting benefits of SCFA? Eat more high-fiber food and probiotic foods, such as:

  • Cheese
  • Butter
  • Yogurt
  • Pickles
  • Sauerkraut
  • Kimchi
  • Kombucha
  • Soy sauce and other fermented sauces
  • Legumes
  • Intact whole grains (not ground into flour)

Try adding plain kefir, plain yogurt with live and active cultures—if you can’t tolerate or don’t enjoy dairy, try dairy-free cashew kefir or probiotic coconut yogurt—to your diet for at least two months to see if you notice any difference.

Watch the amount of sugar added to these products. For example, one popular brand of one cup of strawberry kefir contains 20 grams of total sugar and 8 grams of added sugar. One cup of plain kefir has 12 grams of sugar total (from milk) and 0 grams of added sugar. It might take a minute to get used to the tart, tangy flavor of plain dairy and dairy alternatives, but these lower glycemic options are better for your metabolic health.

This quick list summarizes the probiotic supplements and foods that may help your weight-loss efforts:

  • Multi-strain probiotic supplements
  • Fermented milk products like kefir, yogurt, cheese
  • Non-dairy fermented foods like soy sauce, sauerkraut, pickles, vinegar
  • Fiber-rich carbs like whole grains (gluten-free if intolerant) and legumes 
  • Non-dairy, plant-based fermented products like probiotic coconut yogurt or cashew kefir

Risks of Using Probiotics 

woman suffering from stomach ache laying down on couch

Probiotics are generally considered safe for most people with minimal risk. In some cases, excess probiotics could cause gas or bloating, especially if they are combined with extra fiber.

There are several health conditions where probiotics may not be a good idea. For example, if you are immunocompromised, you should check with your doctor before adding probiotic supplements. People with small intestinal bacterial overgrowth (SIBO) should also avoid probiotics unless recommended a particular strain, as supplementation could add to symptoms.

What About Prebiotics for Weight Loss?

You can’t talk about probiotics without mentioning prebiotics. Prebiotics are the fiber-rich foods your gut bacteria ferment and use as fuel. Without prebiotics, even the best probiotic supplements only provide a temporary solution. Prebiotics allow them to continue to thrive. Prebiotics are also the fiber needed to produce the SCFA mentioned above.

Prebiotic fiber may help your weight loss efforts because it feeds probiotics and supports SCFA production, but also because fiber-rich carbohydrates keep you full and satisfied and support healthy blood sugar management.

Are you interested in learning more about prebiotics and your health? We’ve got you covered:

Conclusion for Effects of Probiotics

The bottom line on probiotics and weight loss is that while we have promising research pointing to the importance of the gut microbiome for optimal health, there isn’t enough evidence to suggest probiotics as the magic wand for weight loss.

In some cases, different strains of probiotics could positively influence the gut environment, which may translate to better metabolic health, but the impact can vary significantly between individuals. While the benefits of probiotics may not include melting belly fat, adding daily servings of fermented foods and prebiotic fiber to a healthy diet may be an additional tool to support weight loss goals and overall health.


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About the author

Sabrina has more than 20 years of experience writing, editing, and leading content teams in health, fitness, nutrition, and wellness. She is the former managing editor at MyFitnessPal.

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