Researchers tested whether a specific probiotic (a type of beneficial bacteria) could improve heart and metabolic health in obese adults over 90 days. While probiotics are often promoted as health boosters, this study found that taking the probiotic supplement alone didn’t improve important health markers like blood pressure, cholesterol, or blood sugar levels. Interestingly, both groups in the study started eating more carbohydrates during the research period, which may have canceled out any potential benefits. The study suggests that probiotics might work better when combined with healthy eating habits rather than as a standalone solution.

The Quick Take

  • What they studied: Whether a probiotic supplement called Lactococcus lactis could improve heart disease risk factors and metabolism in people with obesity
  • Who participated: 52 obese adults (21-26 per group) with at least one heart or metabolic health problem like high blood pressure, high cholesterol, or high blood sugar. The study lasted 90 days.
  • Key finding: The probiotic supplement did not significantly improve any of the measured health markers (blood pressure, cholesterol, blood sugar, or weight) compared to placebo. Both groups actually increased their carbohydrate intake during the study, which may have prevented any potential benefits.
  • What it means for you: Taking a probiotic supplement alone is unlikely to improve your heart or metabolic health without also making dietary changes. This suggests that diet quality matters more than probiotic supplements for managing obesity-related health risks.

The Research Details

This was a randomized controlled trial, which is considered one of the strongest types of research. Researchers randomly assigned 52 obese adults into two groups: one received the probiotic supplement Lactococcus lactis, and the other received a placebo (fake pill). Neither group knew which they were receiving, and the researchers didn’t know either—this is called “triple-blind” and helps prevent bias. The study lasted 90 days, and researchers measured various health markers including weight, body composition, blood pressure, cholesterol levels, and blood sugar at the beginning and end.

The key aspect of this study is what it didn’t do: participants were not given any guidance about what to eat. This is important because it reflects real-world conditions where people make their own food choices. However, it also means that diet changes could have influenced the results in unpredictable ways.

Five participants dropped out of the probiotic group during the study, leaving 21 people in that group and 26 in the placebo group for the final analysis. This dropout rate is relatively small but worth noting.

This research design is important because it tests whether the probiotic works in real-world conditions without strict dietary control. Many previous probiotic studies have shown mixed results, and researchers wanted to see if this particular strain could help without requiring people to also change their diet. The triple-blind design ensures that expectations and bias didn’t influence the results.

Strengths: This was a well-designed randomized controlled trial with blinding, which is a gold standard in nutrition research. The researchers measured multiple health markers, not just one. Weaknesses: The sample size was relatively small (52 people), which limits how confident we can be in the results. The dropout rate in the probiotic group (19%) is notable. Most importantly, the lack of dietary guidance means we can’t separate the effects of the probiotic from the effects of changing eating habits. The study was published in a peer-reviewed journal, which means other experts reviewed it before publication.

What the Results Show

The main finding was that the probiotic supplement did not produce any significant improvements in cardiometabolic risk factors compared to placebo. This means that measures like blood pressure, cholesterol levels, blood sugar, weight, and body fat percentage did not improve more in the probiotic group than in the placebo group.

One interesting and unexpected finding was that both groups increased their carbohydrate intake during the 90-day study period. This increase in carbohydrates occurred in both the probiotic and placebo groups, suggesting it wasn’t related to the supplement itself. This dietary change is important because increased carbohydrate intake, especially refined carbohydrates, could have prevented any potential benefits from the probiotic.

The researchers noted that sodium intake also appeared to be a factor that might have influenced results. Both groups’ dietary patterns seemed to work against any potential metabolic improvements that the probiotic might have offered.

The lack of improvement was consistent across all measured health markers—there were no areas where the probiotic showed even modest benefits.

The study also tracked dietary intake patterns in detail. The finding that carbohydrate consumption increased in both groups is significant because it suggests that without active dietary guidance, people tend to maintain or worsen their eating habits even when participating in a health study. This is a common challenge in nutrition research and reflects real-world behavior. The researchers also noted that the types of carbohydrates consumed (refined vs. whole grain) weren’t clearly distinguished, which could have affected outcomes.

Previous research on probiotics has shown mixed results. Some studies suggest certain probiotic strains may modestly improve some metabolic markers, while others show no benefit. This study adds to the growing evidence that probiotics alone, without dietary changes, are unlikely to produce meaningful improvements in obesity-related health problems. The findings align with recent systematic reviews suggesting that probiotics work best as part of a comprehensive approach that includes diet and lifestyle changes, rather than as standalone treatments.

Several important limitations should be considered: First, the sample size was small (52 people), which means the results might not apply to larger populations. Second, five people dropped out of the probiotic group, which could have affected the results if those people would have responded differently. Third, and most importantly, participants were not given dietary guidance, so we can’t tell if the lack of benefit was due to the probiotic not working or due to poor dietary choices. Fourth, the study only lasted 90 days, which may not be long enough to see metabolic changes. Finally, this was only one specific probiotic strain, so results may not apply to other probiotics.

The Bottom Line

Based on this research, taking a probiotic supplement alone is not recommended as a treatment for obesity-related metabolic problems. However, probiotics may still be worth considering as part of a comprehensive approach that includes healthy eating, regular physical activity, and other lifestyle changes. If you’re interested in probiotics, discuss them with your doctor or registered dietitian. Confidence level: Moderate—this is one study, but it aligns with other recent research showing limited benefits of probiotics without dietary intervention.

This research is most relevant to people with obesity who are looking for ways to improve their heart health and metabolism. It’s particularly important for people considering probiotic supplements as a primary treatment. However, the findings don’t mean probiotics are useless—they suggest that probiotics work best when combined with healthy eating habits. People without obesity-related metabolic problems may not need to worry about these findings.

If you were to take this probiotic, based on this study, you would not expect to see improvements in blood pressure, cholesterol, blood sugar, or weight within 90 days. Realistic expectations for any metabolic improvements would require combining probiotic use with sustained dietary changes over several months to a year.

Want to Apply This Research?

  • Track daily carbohydrate intake and types (refined vs. whole grain) alongside any probiotic supplementation. Users should log grams of carbohydrates and note whether they’re from whole foods or processed sources. This helps identify whether dietary patterns are changing and potentially counteracting supplement benefits.
  • Rather than focusing solely on probiotic supplementation, users should implement a structured dietary change: reduce refined carbohydrate intake and increase whole grains, vegetables, and lean proteins. The app could set a specific carbohydrate reduction goal (e.g., reduce refined carbs by 25%) and track progress weekly.
  • Establish a baseline of current eating habits and metabolic markers (weight, blood pressure if available). If using probiotics, monitor dietary intake weekly to ensure carbohydrate consumption isn’t increasing. Reassess metabolic markers every 4-6 weeks. Track whether dietary changes are being maintained, as this study shows people naturally increase carbohydrate intake without active monitoring.

This research suggests that probiotic supplements alone do not improve heart and metabolic health markers in obese adults without dietary changes. This study does not mean probiotics are harmful or completely ineffective—it means they may work better as part of a comprehensive lifestyle approach that includes healthy eating. If you have obesity-related health concerns, high blood pressure, high cholesterol, or diabetes, consult with your doctor or registered dietitian before starting any supplement. Do not use this study as a reason to stop any medications or treatments prescribed by your healthcare provider. Individual results may vary, and this is one study on one specific probiotic strain.