In female cynomolgus macaques, eating a Mediterranean diet is linked to higher levels of a gut bacterium called Lactobacillus animalis, and higher levels of this bacterium are linked to lower body...

We analyzed one assertion about Lactobacillus animalis and body fat in macaques on a Mediterranean diet, and it supports a possible link. In female cynomolgus macaques, eating a Mediterranean diet — which is rich in plants, nuts, olive oil, and fish — was associated with higher levels of the gut bacterium Lactobacillus animalis. At the same time, higher levels of this bacterium were also linked to lower body fat, suggesting it may be part of a metabolic pattern tied to this kind of eating pattern [1]. We did not find any studies that contradicted this observation. However, this is based on a single assertion, and we only have one data point to work with. The evidence we’ve reviewed so far leans toward a connection between this specific diet, increased Lactobacillus animalis, and reduced body fat in these animals — but we cannot say whether the bacterium causes the change, or if it’s simply present alongside other metabolic shifts. The study focused only on female cynomolgus macaques, so we don’t know if the same pattern appears in males, other primates, or humans. We also don’t know if the bacterium itself is responsible for the lower body fat, or if it’s just a marker of other changes happening in the gut or metabolism due to the diet. More research would be needed to understand the direction of this relationship. For now, what we’ve found suggests that in this specific group of animals, a plant-rich diet and higher levels of Lactobacillus animalis appear together with lower body fat — but we can’t say yet if one directly influences the other.