Researchers discovered that amphotericin B, a medication typically used to treat fungal infections, may help reduce weight gain and improve fat metabolism in mice fed a high-fat diet. The drug appears to work by changing the types of fungi living in the gut and activating brown fat—a special type of fat that burns calories to create heat. After 11 weeks of treatment, mice taking the drug weighed less, had lower cholesterol, and showed improved markers of metabolic health. While these results are promising, this research was conducted only in mice, so scientists will need to test whether these effects work in humans before recommending it as an obesity treatment.
The Quick Take
- What they studied: Whether a common antifungal medicine called amphotericin B could reduce obesity and improve fat metabolism in mice eating a high-fat diet
- Who participated: Male laboratory mice (C57BL/6 strain) divided into three groups: normal diet, high-fat diet without treatment, and high-fat diet with amphotericin B treatment for 11 weeks
- Key finding: Mice treated with amphotericin B gained significantly less weight, had lower body fat (especially around the belly), higher levels of beneficial brown fat, and better cholesterol levels compared to untreated mice on the same high-fat diet
- What it means for you: This research suggests a new potential approach to treating obesity by modifying gut fungi, but it’s still in early stages. The findings are promising but were only tested in mice, so human studies would be needed before considering this as a treatment option
The Research Details
Scientists divided male mice into three groups: one group ate normal food, while two groups ate high-fat food. One of the high-fat groups received amphotericin B (a medication given by mouth) while the other received no treatment. After 11 weeks, researchers measured multiple things including body weight, fat tissue amount, blood cholesterol levels, and the types of fungi living in each mouse’s gut. They also examined the actual structure of fat cells under a microscope and measured which genes were turned on or off in the fat tissue. Additionally, they isolated specific fungi from the mice’s intestines and tested whether these fungi could lower cholesterol in laboratory dishes.
This approach is important because it looks at obesity from a new angle—focusing on the microscopic fungi living in our digestive system rather than just calories in and out. Understanding how these gut fungi influence fat storage and burning could lead to completely new ways to treat obesity that work differently than current medications
This is a controlled laboratory study where researchers carefully controlled all variables (diet, medication dose, mouse genetics, and living conditions), which allows them to draw clear conclusions about cause and effect. However, because it was only done in mice, we cannot automatically assume the same results would happen in humans. The study included multiple measurements (weight, blood tests, tissue examination, genetic analysis, and microscopic analysis) which strengthens the findings
What the Results Show
Mice treated with amphotericin B while eating a high-fat diet showed several important improvements compared to untreated mice on the same diet. First, they gained significantly less weight overall and had much less fat stored in their belly area (epididymal fat). Second, they developed more brown fat—the type of fat that burns calories to produce heat rather than storing energy. Third, their blood cholesterol levels improved, showing better lipid profiles. Fourth, their individual fat cells were noticeably smaller, suggesting the body was breaking down fat more efficiently.
At the genetic level, the treated mice showed increased activity of three important genes involved in burning fat and producing heat: PPARγ, PGC1α, and UCP1. These genes essentially tell fat cells to work harder at burning calories instead of storing them. The researchers also found that the medication improved the health of the intestinal barrier—the protective lining of the gut—by increasing levels of protective proteins called Occludin and Muc2.
The most interesting secondary finding was how the medication changed the types of fungi living in the mice’s guts. Amphotericin B increased the amount of a beneficial fungus called Rhodotorula while decreasing harmful fungus called Aspergillus. When researchers isolated a specific strain of Rhodotorula (called R. mucilaginosa DM2025) and tested it in laboratory dishes, this fungus showed the ability to lower cholesterol levels. This suggests that the beneficial effects might come partly from promoting the growth of helpful fungi that naturally fight obesity and improve cholesterol
Previous research had shown that amphotericin B could improve liver health in mice eating high-fat diets, but this is the first study to examine its effects on overall obesity and the gut fungi involved. The findings align with growing scientific evidence that gut fungi (the mycobiome) play an important role in obesity and metabolism, similar to how gut bacteria have been shown to influence weight. This research adds an important new piece to our understanding of how different microorganisms in our digestive system affect our weight and health
This study has several important limitations that readers should understand. First and most importantly, all results come from mice, not humans—mouse metabolism works differently than human metabolism, and results don’t always transfer to people. Second, the study only looked at male mice, so we don’t know if the same effects would occur in females. Third, the exact dose and how it would translate to human medicine is unclear. Fourth, the study lasted only 11 weeks, so we don’t know if benefits would continue long-term or if the body might adapt. Finally, while the researchers identified one beneficial fungus, they didn’t fully explain all the ways amphotericin B might be working to reduce obesity
The Bottom Line
Based on this mouse research, amphotericin B shows promise as a potential obesity treatment, but it is far too early to recommend for human use. The confidence level for these findings is moderate—they’re solid laboratory science but need human testing. Anyone interested in this research should wait for human clinical trials before considering it as a treatment option. Current evidence-based approaches for obesity (balanced diet, regular physical activity, and medical supervision) remain the recommended first-line treatments
This research is most relevant to obesity researchers, pharmaceutical companies developing new treatments, and people struggling with obesity who are interested in emerging therapies. It may be particularly interesting to those with high cholesterol alongside obesity. However, people should NOT attempt to use amphotericin B for weight loss outside of a clinical trial, as it’s a powerful medication with potential side effects designed for treating fungal infections. This research is not yet ready for general public application
In the mouse study, significant changes appeared within 11 weeks. If this were to be tested in humans, researchers would likely start with small safety studies lasting weeks to months, followed by larger effectiveness studies lasting months to years. Realistically, if amphotericin B proves safe and effective in humans, it would likely take 5-10 years of clinical trials before it could potentially be approved as an obesity treatment
Want to Apply This Research?
- Users interested in gut health could track their daily intake of foods that promote beneficial fungi (fermented foods, fiber-rich foods, foods with natural antifungals) and monitor how they feel, energy levels, and weight changes over 4-week periods
- While waiting for human research on amphotericin B, users can support healthy gut fungi by eating more fiber (vegetables, whole grains, legumes), consuming fermented foods (yogurt, kefir, sauerkraut), reducing ultra-processed foods, and maintaining regular physical activity—all proven approaches to support beneficial gut microorganisms
- Users should track weekly weight, waist circumference measurements, energy levels, and digestive health markers (bloating, regularity, digestive comfort) to see if gut-supporting dietary changes correlate with improvements in these areas. This creates a personal baseline for understanding how their individual gut health affects their weight and wellbeing
This research was conducted in mice and has not been tested in humans. Amphotericin B is a prescription medication used to treat fungal infections and should only be used under medical supervision for its approved purposes. Do not attempt to use amphotericin B for weight loss or obesity treatment outside of a clinical trial setting. This article is for educational purposes only and should not be considered medical advice. Anyone seeking treatment for obesity should consult with their healthcare provider about evidence-based options including diet, exercise, behavioral changes, and FDA-approved medications. Future human clinical trials would be needed before amphotericin B could be considered as a potential obesity treatment.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.