Probiotics are live microorganisms that contain "good" bacteria and yeasts. These "good" organisms can improve your gut and overall health. Some researchers believe that probiotics can also help with weight loss.

Your gastrointestinal (GI) tract is full of microorganisms, including bacteria, viruses, and fungi. This community of microorganisms that naturally live in your gut is known as your gut microbiome. The types of organisms you have in your gut can affect your overall health and risk for disease.

The gut microbiome plays a role in your body getting nutrients and energy from the foods you eat. If your gut microbiome has an imbalance of "good" and "bad" bacteria, it can affect how well your body breaks down food, absorbs nutrients, and fights infections. This can also raise your risk for things like weight gain and inflammation.

Studies have shown a difference in the gut bacteria of people with obesity compared to those without obesity. Researchers suggest this is due to overall diet and the amount of calories consumed. When the gut doesn't break down the nutrients and energy from food properly, your body stores more energy in your fat tissue, leading to weight gain.

Probiotics contain "good" bacteria that help with gut health. These beneficial bacteria help replace the "bad" or harmful bacteria in your gut, improving digestion and your immune system. Probiotics can also help:

• Lower inflammation
• Improve blood fat and cholesterol levels
• Improve how well insulin works in your body (insulin sensitivity)

Some research has shown that probiotics may help with weight loss, especially in people with overweight or obesity. Probiotics have been shown to:

• Lower body weight and body fat
• Improve body mass index (BMI)
• Decrease the distance around your waist (waist circumference)
• Improve insulin resistance and fat levels in your blood, both of which can affect your weight
• Help regulate your appetite, making you feel fuller quicker

Most studies found that probiotics were most effective for weight loss when used in combination with a low-calorie diet and increased physical activity.

Overall, studies show that the effect of probiotics on weight loss may depend on many factors, including:

• Probiotic strain
• Probiotic dose
• How long you take a probiotic (many studies are longer than 12 weeks)
• Age
• Starting weight

A 2019 research review found that probiotics may have a small effect on lowering waist circumference, but have no effect on weight or BMI. Another 2021 study found that probiotics help lower BMI and waist and hip circumference, but did not significantly lower overall weight.

research is needed to understand the role probiotics may play in weight loss.

Which Strains Help With Weight Loss?

Probiotics are available in various strains. Specific strains are more common and may be more useful for certain health conditions. Studies have shown that two strains are most useful for weight loss:

• Lactobacillus: The Lactobacillus strain has been shown to help with weight loss and gut health. Lactobacillus is one of the most common and popular probiotic strains.
• Bifidobacterium: Researchers have found that the Bifidobacterium strain is also one of the best options to help with weight loss.

Some researchers have found that a combination of both Lactobacillus and Bifidobacterium strains is most effective at lowering weight. studies are needed to understand how these strains may work together.

Dosing depends on the probiotic's bacteria strain and the product you are using. Read the label of any product you are taking and talk with a healthcare provider for dosing information.

Probiotics can naturally be found in certain fermented and daily foods. These include yogurt, kefir, some cheeses, sauerkraut, and kimchi. Probiotics are also available in certain products, like drinks, cereal, chocolate, and nutrition bars.

Products high in Lactobacillus and Bifidobacterium strains include yogurts and other fermented foods.

Probiotic supplements are available in many forms, like capsules, powders, and liquids. Doses are typically measured in colony-forming units (CFUs), which represents the number of viable (live) cells available. A high CFU count does not necessarily mean the product will work better than a product with a lower CFU count. Be sure to read the package information to understand the CFU count of a product.

Possible probiotic side effects include:

• Abdominal pain
• Constipation
• Diarrhea
• Gas
• Nausea

These side effects usually go away after a few weeks of taking a probiotic.

Probiotics are considered safe for most adults without health conditions. The risk for harmful side effects is higher in people with certain illnesses and weakened immune systems. This can include:

• People with immune system-related illnesses, like HIV
• People receiving chemotherapy
• People who have had an organ transplant and are on medications to weaken the immune system (immunosuppressants)

Using probiotics in these groups can lead to serious blood infections and make other medications you are taking less effective.

If you have any immune system-related illnesses or a weakened immune system, talk to your healthcare provider before starting a probiotic.