Scientists wanted to understand how eating lots of fatty foods changes the tiny bacteria living in our stomachs, and whether a specific probiotic called Bifidobacterium infantis could help. They fed rats three different diets for 8 weeks: normal food, high-fat food, and high-fat food with the probiotic added. The rats eating high-fat food gained a lot of weight and had changes in their gut bacteria. Interestingly, the probiotic also changed the bacteria in the stomach, and some bacterial types were linked to how much weight the rats gained. This research suggests that the bacteria in our guts might play a role in obesity, and probiotics could potentially help, but more research is needed.

The Quick Take

  • What they studied: Whether a specific probiotic (a type of helpful bacteria) could prevent weight gain and change gut bacteria in rats eating a high-fat diet
  • Who participated: Rats divided into three groups: one eating normal food, one eating high-fat food, and one eating high-fat food plus probiotic supplements for 8 weeks
  • Key finding: Rats on high-fat diets gained significantly more weight and had different gut bacteria compared to rats on normal diets. The probiotic changed the gut bacteria, and certain bacterial types were strongly connected to weight gain
  • What it means for you: This early research suggests that the bacteria in our digestive system may influence weight gain, and probiotics might help manage this. However, this was done in rats, so we need human studies before making recommendations

The Research Details

Researchers divided rats into three groups and fed them different diets for 8 weeks. The first group ate normal-fat food, the second ate high-fat food, and the third ate high-fat food plus a probiotic supplement called Bifidobacterium infantis 35624. The scientists measured how much weight each rat gained and checked their blood sugar and insulin levels at the end. They also analyzed the bacteria living in each rat’s stomach to see what types were present and how they differed between groups.

This type of study is called an experimental design because the researchers controlled exactly what the rats ate. By comparing three groups, they could see the effects of high-fat food alone and then see if adding the probiotic made a difference. The 8-week timeframe allowed enough time for changes to happen and be measured.

Understanding how diet changes the bacteria in our guts is important because these bacteria affect our health in many ways, including how our bodies handle weight and blood sugar. By testing a probiotic in a controlled setting with rats, scientists can learn whether probiotics might help before testing them in humans. This approach helps identify which bacteria might be important for weight management.

This study was published in a peer-reviewed medical journal, which means other experts reviewed it before publication. The study used a clear experimental design with different groups to compare. However, the exact number of rats used wasn’t specified in the abstract. Since this was done in rats, results may not directly apply to humans. The study measured important markers like weight, blood sugar, and insulin levels, which are relevant to obesity.

What the Results Show

The high-fat diet group showed dramatic results: rats eating high-fat food gained significantly more weight than rats eating normal food (the difference was very statistically significant, with p < 0.001, meaning there’s less than a 0.1% chance this happened by random chance). The rats on high-fat diets also had higher blood sugar and insulin levels compared to the normal-diet group.

When scientists examined the gut bacteria, they found that each group had a different mix of bacterial species. Some specific types of bacteria were strongly associated with how much weight the rats gained. This suggests that certain bacteria may play a role in weight gain. Interestingly, both the high-fat diet and the probiotic supplement caused changes in the gut bacteria, meaning the probiotic didn’t simply restore the bacteria to normal—it created its own different bacterial community.

The study found that specific bacterial species were significantly linked to body weight differences between groups. This suggests that not all gut bacteria are equal when it comes to weight management—some types may promote weight gain while others might protect against it. The fact that the probiotic changed the bacterial community in a different way than the high-fat diet alone suggests probiotics work through altering the balance of bacteria in the stomach.

Previous research has shown that obesity is connected to changes in gut bacteria and low-grade inflammation in the body. This study supports that connection and adds evidence that specific bacterial types may be involved. The idea that probiotics could help manage obesity is not new, but this research provides more detail about how one specific probiotic affects the bacterial community. However, human studies on this probiotic and obesity are limited, so this research fills a gap in our understanding.

This study was conducted in rats, not humans, so the results may not directly apply to people. The abstract doesn’t specify how many rats were used, making it harder to assess the study’s strength. The study lasted only 8 weeks, which is relatively short for understanding long-term effects. The researchers didn’t explain exactly which bacterial species were beneficial or harmful, so we don’t yet know which specific bacteria to target. Finally, this was a single study, so the findings need to be confirmed by other researchers before making strong conclusions.

The Bottom Line

Based on this research alone, we cannot recommend probiotics as a weight-loss treatment. This is early-stage research in animals that suggests probiotics may influence gut bacteria and potentially weight gain. If you’re interested in probiotics for weight management, talk to your doctor. Proven approaches for weight management include eating balanced meals, limiting high-fat and high-sugar foods, and getting regular exercise. More human studies are needed before probiotics can be recommended specifically for obesity prevention.

This research is most relevant to scientists studying obesity and gut bacteria, and to people interested in how probiotics work. It’s preliminary information, not a treatment recommendation. People with obesity, those at risk for weight gain, and anyone interested in gut health may find this interesting, but shouldn’t change their habits based on this single animal study. Healthcare providers studying obesity management should note this as emerging research worth following.

Since this is an animal study, we don’t know how quickly effects would appear in humans, or if they would appear at all. The rats showed changes over 8 weeks, but human bodies work differently. If human studies eventually confirm these findings, benefits would likely take weeks to months to become noticeable. Don’t expect immediate results from any intervention based on this research.

Want to Apply This Research?

  • Track daily weight (same time each day), weekly average weight change, and note any probiotic supplements taken. Also track meals high in fat to see if there’s a pattern with weight changes
  • If you want to test this yourself (with doctor approval), you could use an app to log: daily probiotic intake, meals eaten (especially fat content), weight measurements, and energy levels. This creates a personal record to discuss with your healthcare provider
  • Over 8-12 weeks, track weight trends weekly rather than daily (daily fluctuations are normal). Also monitor how you feel—energy levels, digestion, and overall wellness. Keep notes on diet quality alongside any probiotic use. Share this data with your doctor to see if there are any patterns worth investigating further

This research was conducted in rats and has not been tested in humans. The findings are preliminary and should not be used as medical advice. Probiotics are not proven treatments for obesity. Before taking any probiotic supplement, especially if you have obesity, diabetes, or other health conditions, consult with your doctor or registered dietitian. Do not replace proven weight management strategies (balanced diet and exercise) with probiotics based on this study. Individual results vary greatly, and what works in rats may not work in people.