Probiotics are live microorganisms that have health benefits when eaten (
They’re found in both supplements and fermented foods.
Probiotics may improve your immune function and digestive and heart health, among other benefits (
Several studies also suggest that probiotics can help you lose weight and belly fat.
Hundreds of microorganisms reside in your digestive system.
The majority of these are friendly bacteria that produce several important nutrients, including vitamin K and certain B vitamins.
They also help break down fiber, which your body can’t digest, turning it into beneficial short-chain fatty acids like butyrate (
There are two main families of good bacteria in the gut: bacteroidetes and firmicutes. Body weight seems to be related to the balance of these two families of bacteria (
Both human and animal studies have found that moderate-weight people have different gut bacteria than those with overweight or obesity (
In the majority of those studies, people with obesity had more firmicutes and fewer bacteroidetes, compared with moderate-weight people.
However, several studies have failed to find a connection between the firmicutes-to-bacteroidetes ratio and obesity (
People with obesity tend to have less diverse gut bacteria than lean people. What’s more, those with obesity who have less diverse gut bacteria tend to gain more weight than people with obesity who have more diverse gut bacteria (
Some animal studies also show that when gut bacteria from mice with obesity were transplanted into the guts of lean mice, the lean mice developed obesity (
Studies suggest that gut bacteria may play a powerful role in body weight regulation.
The methods by which probiotics affect body weight and belly fat aren’t yet well understood.
Probiotics seem to influence appetite and energy usage via the production of acetate, propionate, and butyrate, which are short-chain fatty acids (
It’s thought that certain probiotics may inhibit the absorption of dietary fat, increasing the amount of fat excreted with feces (
In other words, they make your body “harvest” fewer calories from the foods you eat.
Certain bacteria, such as those from the Lactobacillus family, have been found to function in this way (
Probiotics may also fight obesity in other ways, including:
- Releasing appetite-regulating hormones: Probiotics may help release the appetite-reducing hormones glucagon-like peptide-1 (GLP-1) and peptide YY (PYY). Increased levels of these hormones may help you burn calories and fat (
- Increasing levels of fat-regulating proteins: Probiotics may increase levels of the protein angiopoietin-like 4 (ANGPTL4). This may lead to decreased fat storage (
20, 21, 22).
Strong evidence links obesity to inflammation throughout the body. By improving the health of your gut lining, probiotics may reduce systemic inflammation and protect against obesity and other diseases (
More research is needed to fully understand these mechanisms.
Probiotics may reduce the number of calories you absorb from food. They also affect levels of hormones and proteins related to appetite and fat storage, as well as potentially reduce inflammation, which can drive obesity.
A recent review of well-designed studies on probiotics and weight loss in people with overweight and obesity suggests that probiotics can help you lose weight and lower your body fat percentage (
In particular, studies have found that certain strains of the Lactobacillus family can help you lose weight and belly fat.
In one study, eating yogurt with Lactobacillus fermentum or Lactobacillus amylovorus reduced body fat by 3–4% over 6 weeks (29).
Another study of 125 overweight dieters investigated the effects of Lactobacillus rhamnosus supplements on weight loss and weight maintenance (
Women taking the probiotics lost 50% more weight over 3 months, compared with those taking a placebo pill. They also continued to lose weight during the weight maintenance phase of the study.
In one well-designed study, 114 adults with obesity were given either the probiotic Lactobacillus sakei or a placebo for 12 weeks. Those taking the probiotic experienced significant decreases in both body fat mass and waist circumference (
Of all the probiotic bacteria studied to date, Lactobacillus gasseri shows some of the most promising effects on weight loss. Numerous studies in rodents have found that it has anti-obesity effects (
Additionally, studies in adults have shown promising results (
One study that followed 210 people with significant amounts of belly fat found that taking Lactobacillus gasseri for 12 weeks reduced body weight, fat around organs, body mass index (BMI), waist size, and hip circumference.
What’s more, belly fat was reduced by 8.5%. However, when participants stopped taking the probiotic, they gained back all of the belly fat within 1 month (
Other strains of probiotics may also help reduce weight and belly fat.
In an 8-week study, women with overweight or obesity took either a probiotic that included strains of both Lactobacillus and Bifidobacterium or a placebo, along with following a dietary intervention.
Those consuming the probiotic lost significantly more belly fat than those taking a placebo (
Another study in 135 people with significant amounts of belly fat found those who took Bifidobacterium animalis subsp. lactis daily for 3 months lost significantly more belly fat and had reduced BMI and waist circumference, compared with those taking a placebo.
These results were especially pronounced in women (
Several strains of probiotics in both the Lactobacillus and Bifidobacterium family have been shown to reduce weight and belly fat. Lactobacillus gasseri appears to be one of the most effective.
Losing weight is not the only way to fight obesity. Preventing unwanted weight gain in the first place may be even more valuable in avoiding obesity.
In one 4-week study, taking a probiotic formulation called VSL#3 reduced weight gain and fat gain in people following a diet that provided 1,000 extra calories than they needed per day (
Those in the probiotic group gained less fat, although they didn’t experience any significant changes in insulin sensitivity or metabolism.
This indicates that some probiotic strains might prevent weight gain in the context of a high calorie diet. However, this needs to be studied further.
Certain probiotic strains may be able to reduce weight gain in people following a high calorie diet.
Not all studies have found that probiotics aid weight loss.
Some studies have found that certain probiotic strains might lead to weight gain — not weight loss.
One recent review found that probiotics’ effects on body weight depend on which species and strains are used. For instance, while one strain of Lactobacillus gasseri reduced weight gain compared with a control, another strain promoted weight gain (
Not all probiotics aid weight loss, and some may even cause weight gain. The effects depend on the probiotic strain and may vary by individual.
Probiotics offer a wide range of health benefits.
However, their effects on weight are mixed and seem to depend on the type of probiotic.
Evidence indicates that Lactobacillus gasseri may help people with obesity lose weight and belly fat. Additionally, a probiotic supplement blend called VSL#3 may reduce weight gain in those on a high calorie diet.
At the end of the day, certain types of probiotics may have modest effects on your weight, especially when combined with a healthy, whole-foods diet.
Nevertheless, there are many other reasons to take a probiotic supplement.
They can improve your digestive health and cardiovascular risk factors, reduce inflammation, and even help fight depression and anxiety.