Your gut is a teeming warehouse of trillions of bacteria—some of those are good and protective while others are not. When everything is functioning optimally, your body is able to maintain a healthy balance. But it doesn't take much to throw it out of whack.
When the bacteria in the intestinal tract (i.e., your gut microbiota) lack in volume or diversity, or the wrong types of microorganisms start to flourish, it not only can affect your health, but it can also make healthy weight maintenance more difficult.
Why? Because your gut bacteria are intricately connected with not only your digestive system, but also your metabolism and whole-body health.*
A probiotic supplement that contains science-backed strains of good bacteria can help maintain or restore a healthy microbial balance to your digestive system.*
These supplements deliver certain probiotic strains, such as those from genera Lactobacillus and Bifidobacterium, and when taken regularly, they lay down the good bugs you want in your gut, and over time, your health will thank you for it.*
Does gut health influence weight?
But it presents a chicken-or-the-egg question—does the microbial imbalance cause weight gain or does the extra weight somehow change the balance of bacteria?
Renowned integrative physician Robert Rountree, M.D., thinks the evidence is clear, "There is no question that the bacteria in our gut can affect our weight."* He first cites animal studies, in which obese mice are given a fecal transplant2 from lean mice and, consequently, lose weight and body fat.*
This might be due to how gut bacteria interact with our cells and digestive process.
One study found that simply overeating can tip the balance in favor of bad bacteria3. The problem? As Rountree explains it, "Certain bacteria are better at extracting energy from food than others."
In addition, gut bacteria play a role in appetite regulation and satiety (the feeling you get after eating a huge, delicious meal).*
When the "good" bacteria outnumber the "bad," the levels of short-chain fatty acids increase in the gut, triggering the production of hormones5 that regulate appetite.* So, if these hormones are out of balance, then you might not get the signal that you are full.
The result is a weight-gain cycle—you overeat and the bad bacteria increases in your gut, possibly increasing body fat and lowering levels of short-chain fatty acids that would otherwise help control your appetite, causing you to eat more, which increases the bad bacteria, which...well, you get the idea.
The best probiotic strains for weight maintenance.*
Although researchers identify these strains with a combination of unique letters and numbers, not all supplement labels actually list the strains of bacteria they contain—sometimes you'll find only the genus and species—such as Lactobacillus rhamnosus or Bifidobacterium lactis.
In contrast, mbg's director of scientific affairs Ashley Jordan Ferira, Ph.D., R.D.N. explains that, "high-quality and transparent supplement brands will absolutely identify the probiotic at the strain level (genus, species, and strain). Look for those three pieces of info, because that's how probiotics are clinically researched, by strain."
Exciting research continues to emerge for this specific area of probiotic evidence.
For your weight-maintenance efforts, we've compiled the top contender probiotic strains rooted in science; the most well-researched strains to support a healthy weight include:*
Each of these strains has been specifically studied via clinical trials for their impact on weight and has been found to have favorable effects on weight, body fat, waist circumference, visceral fat, and glucose control.*
So, can a probiotic supplement help with weight?
Although more research is needed to understand the complex interactions between the gut microbiome and weight maintenance, Rountree says, "I think we are on the verge of discovering what bacteria might be causing this obesity problem," and recent clinical studies in the past five to 10 years are zeroing in on the possible benefits of probiotic supplements to aid in a healthy weight.*
In a study of 125 men and women with obesity, published in the British Journal of Nutrition, it was found that probiotic supplementation helped women lose weight and maintain their weight loss11 over a 24-week period while following a reduced-calorie diet.*
The women taking the probiotic supplement lost significantly more weight than women in the control group, who also followed a reduced-calorie diet but did not take the probiotic supplement.*
Another study, this one of 90 adults with overweight and obesity, found that taking a probiotic supplement for 12 weeks had a favorable effect on participants' visceral fat12—the fat that accumulates near the liver, stomach, and intestines and increases the risk for many diseases.*
These and other studies have used individual strains and combinations of probiotic bacteria, with beneficial outcomes for weight maintenance.*
In fact a comprehensive 2018 systematic review and meta-analysis13 of over 20 probiotic studies on weight concluded that probiotics are "essential tools [for] obesity and can lead to significant decreases in BMI, weight, and fat mass."* That's compelling science.
Don't forget about diet and lifestyle.
If you take a probiotic supplement, then it can offer a weight-maintenance advantage, but that alone won't be enough to knock off the extra pounds.*
Eating a nutrient-dense, colorful dietary pattern, moving often, and quality sleep are still the pillars of long-term weight success.
The research on probiotics and weight is cutting edge and promising. Scientists have already identified several strains that can support healthy weight.*
These strains, like Bifidobacterium lactis B420, have been found to have favorable effects on weight, body fat, waist circumference, visceral fat, and blood sugar.*
Densie Webb Ph.D., R.D. is a freelance writer, editor, and consultant. She received her Ph.D. in Nutrition from Texas Woman's University.
She has worked with media, health professionals, and the scientific community, attending and reporting on scientific meetings, researching topics, tracking trends, and assisting in the preparation of manuscripts for publication in scientific journals. She has also been the author or editor of seven health and nutrition books for consumers and is currently a freelance writer and editor of articles on health and nutrition. She is also an author of two published novels, with a third under contract.