Probiotics Are Touted as The Latest Shortcut for Shedding Pounds. But Are They?

Matthew Kadey, M.S., R.D.
Photo credit: Lakota Gambill
Photo credit: Lakota Gambill

From Bicycling

Over the years, people have sought out all sorts of shortcuts to shed pounds: juice cleanses, marathon sauna sessions, or even cayenne-laced body creams, all of which have proven pretty much useless for long-term success. Now, probiotics are being proposed as tiny fat bombs. So is consuming bugs a legit weight-loss tactic, or just another passing trend?

What are probiotics?

Probiotics are live microorganisms, predominantly the Lactobacillus and Bifidobacterium strains, that can populate your gastrointestinal tract when consumed via fermented foods or supplements. The community of microorganisms that lives on us and in us is called the microbiome. Once the probiotics fertilize your gut and build up your microbiome in favor of the good guys, these beneficial critters can help you properly digest dinner, aid in the production of certain vitamins, and bolster your immune system (and who isn’t thinking about immunity these days).

There are two first families of bacteria in your gut: The good Bacteroidetes and the not-so-great Firmicutes—you want more of the former. And if you are Zwifting up a storm these days, it’s good to know that a study in the journal Nutrients suggests certain probiotics may help shield athletes from upper respiratory tract infections. The happier your gut, the better your body functions.

Consuming probiotics for better gut functioning and keeping colds at bay is one thing, but you may have heard that emerging research suggests some of the trillions of minuscule microbes in your gut’s natural ecosystem may help improve your power-to-weight ratio by making it easier to slim down, too.

What does the science say?

Some promising research associating probiotics with numbers on the scale hails from a study in the British Journal of Nutrition where obese women enrolled in a weight loss program who received the probiotic Lactobacillus rhamnosus shed more body weight (a little under four pounds) over three months and did a better job at keeping it off than those who took a placebo. Additionally, the women taking a probiotic supplement continued to lose more weight in the weight-maintenance stage after they finished dieting.

For some reason, there were no real differences in weight loss among male participants. However, one study in Obesity found daily supplementation with a probiotic containing eight strains of live bacteria helped protect men against weight gain when eating a high-calorie, high-fat diet. Canadian scientists discovered that when overweight adults consumed a yogurt spiked with Lactobacillus amylovorus and Lactobacillus fermentum, they lost more body fat (a total of 3 to 4 percent) then when they did not spoon up the bug-rich dairy. In this study, people who drank fermented milk laced with a strain of Lactobacillus gasseri lost a bit more than 8 percent of their belly fat over 12 weeks. However, when they stopped drinking the milk, fat loss ceased suggesting that constant consumption is necessary.

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“Based on the available research, it’s promising that the consumption of probiotics and our microbiome plays a role in weight loss and weight management,” says Caroline M. Apovian, M.D., Professor of Medicine and Pediatrics in the Section of Endocrinology, Diabetes, Nutrition and Weight Management at Boston University School of Medicine.

Exactly how probiotics encourage weight loss is not crystal clear yet, but several theories exist. “Different microbiota have a differing ability to extract energy from food and regulate our energy balance that may lead to changes in body composition,” Apovian notes. For instance, certain probiotics may block fat absorption and increase the excretion of fat through the stool, thus trimming the number of calories the body absorbs.

Apovian explains that our microbiome is also likely involved in the control of food intake and satiety by altering hormones in the gut that send satiety signals to the brain to put the brakes on overeating. This last point is buttressed by an investigation into the association between probiotics and body weight published in the journal Nutrients, which suggests consuming lactobacillus rhamnosus may impact our gut-brain axis to regulate appetite. In other words, the probiotic sends signals to our brain to tell us that we are full and don’t need to stuff in a second helping of spaghetti.

And you may not need to take probiotics directly to reap their belly-shrinking powers. Researchers from Arizona State University have uncovered evidence to suggest that a high-fiber diet can increase levels of beneficial Prevotella bacteria in your gut, and this could be one reason why research has linked eating more dietary fiber with less risk for overweight or obesity. Some evidence shows that our gut microbiota breaks down the fiber in items like fruits and vegetables into helpful compounds including anti-inflammatory short-chain fatty acids.

Sounds great. What’s the catch?

All of this is very preliminary and largely based on speculation and educated theories. There’s simply not enough evidence to support a cause-and-effect relationship between probiotic consumption, your gut bacteria, and waistline size yet.

“We are a long way from knowing which strains would have the most benefits or how to provide that benefit,” cautions Apovian. So while a specific probiotic type may have the power to improve digestive health, it may do nothing to help you get lean.

Concerning dosage, do you need to consume 1 billion, 10 billion, or 100 billion live bugs? No answers there yet.

And will probiotics work on generally fit individuals who just have a couple of pounds they would like to lose? When not performed on animals, most research to date has been conducted on obese individuals whose body weight might be more sensitive to changes in the microbiome. “I do think that there is enough evidence to show that obesity is associated with a gut microbiome that is unbalanced towards bacteria in the undesirable Firmicutes family that produce signaling molecules which promote fat production,” Apovian says.

She adds that a typical high-fat, calorie-dense Western diet can contribute to a dysfunctional microbiome that is associated with obesity as opposed to leanness. While there is some animal data to show that certain probiotics encourage weight loss, Apovian stresses that similar trials in humans have been much less impressive.

The makeup of the gut microbiome does not seem to be the underlying cause of obesity, so focus on healthy eating and exercise habits, and you could both lose some weight and improve the good microbes that make it easier to maintain healthier body weight.

And even if we can eventually prove that taking certain probiotics can help with weight loss efforts, it’s not a one-and-done deal. Since probiotics won’t colonize your gut permanently, once you stop consuming the food or supplement, the benefits will likely dissipate quickly.

The bottom line:

As it stands, probiotics are not a weight loss magic bullet. At best, experts like Apovian say they could be one part of a comprehensive weight-loss program that places more stress on eating better and exercising more often. With that said, manipulating our microbiome by way of consuming probiotics can play a role in our overall well-being so taking a probiotic supplement or better yet, consuming probiotic-rich fermented foods daily likely won’t hurt.

These include yogurt, kefir, kombucha, miso, aged cheese, tempeh, and sauerkraut. And a diet high in fiber via vegetables, legumes, and whole grains will give these critters something to nosh on so they can thrive. “No amount of probiotic supplement will make up for a lousy diet full of processed foods,” Apovian concludes.

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