Ladies: Good Bacteria In Yogurt May Be Good For Waistlines, Too

By Maria Godoy

Published February 5, 2014 at 1:52 PM EST

A probiotic commonly found in yogurt seems to help women lose more weight and fat, a recent study finds. But you still have to eat healthy to see an effect.

Ladies, if that Super Bowl Sunday pitch from '90s heartthrob John Stamos didn't leave you craving more yogurt, here's some science that might do the trick: There's tantalizing new research suggesting that some friendly bacteria commonly found in yogurts may help women shed more weight while on a diet and keep it off.

The findings, published recently in the British Journal of Nutrition, also hint at how probiotics — live cultures of supposedly beneficial microbes — in our food might be interacting with the tiny microbes that live in our guts, which may play a role in the obesity epidemic.

In the study, researchers from Universite Laval in Quebec, Canada, and yogurt giant Nestle recruited 125 obese but otherwise healthy men and women for a 24-week-long study. For the first 12 weeks, all of the subjects were put on a supervised, calorie-restricted weight-loss diet. The second 12 weeks was a weight-maintenance period: Participants got a personalized diet plan but no more calorie restrictions.

During the entire 24-week period, half the study subjects got two pills a day containing a probiotic known as Lactobacillus rhamnosus. Each pill contained roughly the same amount of this bacteria as you would get in a single serving of yogurt. The other half received placebo pills.

At the end of the first 12 weeks, the women taking the probiotics lost an average of 9.7 pounds, versus the 5.7-pound average weight loss for women taking the placebo.

But here's the kicker: During the second 12 weeks, the placebo group of women maintained their weight loss, but the women who were taking probiotics kept right on losing weight, for a total average weight loss of 11.5 pounds.

In other words, the women in the probiotics group lost nearly twice as much weight overall on average. They also lost more fat mass. What's more, women in the probiotic group also saw a 25 percent drop in their blood levels of leptin, a hormone that seems to be a key player in regulating appetite and metabolism.

While the researchers only looked at one type of probiotics, they say other probiotics found in dairy products may well have a similar effect.

So what about the fellows, you ask? The menfolk who took the probiotics didn't seem to lose any more weight than those who took the placebo.

"We don't know why the probiotics didn't have any effect on men. It may be a question of dosage, or the study period may have been too short," Angelo Tremblay, an obesity researcher at Laval who led the research, said in a statement.

One interesting difference among the genders occurred in the gut. The men taking probiotics didn't experience any significant changes in the makeup of the microbes living in their stomachs.

But it was a different story altogether in women: The probiotic treatment, the researchers note, appeared to "substantially and significantly" reduce the amount of bacteria in the Lachnospiraceae family in the ladies' bellies. Those beasties belong to a group of bacteria that have previously been linked with obesity — although, as the researchers note, scientists are still trying to pin down exactly what role they may play.

That hint that the probiotics might somehow be affecting the women's gut microbiome is intriguing. That's because in recent years, studies have shown that lean people have more species and more numbers of critters living in their gut than obese people do. And in one highly publicized study from last year, researchers were able to make mice lean or obese by altering their gut bacteria.

"The link between the gut microbiota ... and weight maintenance is very compelling," Colin Hill, a microbiologist at University College Cork in Ireland, who was not involved in the study, tells The Salt in an email.

But here's the thing: The bacteria that live in our gut arecompletely different from the ones we consume in yogurt or probiotic supplements. In fact, Lactobacillus and other bacteria in yogurt don't even stick around for long in our bodies after we eat them. And while evidence is growing that eating probiotics may have an overall good effect on health, researchers are still trying to puzzle out which strains might be helpful, why and how.

So what everybody in the probiotics world wants to know is: Can the party-hopping bugs in your Yoplait really influence the long-term inhabitants in your belly?

The new study has "thrown up several interesting leads," says Hill, but it really doesn't answer those big questions.

One thing that's clear, though: No matter how those friendly bugs in our food may be working, you still have to eat the right stuff to get the weight loss effect. In other words: Keep the kale salads coming; hold the burger and fries.