A new study has found that gaining weight as a result of poor diet is linked to impaired cognitive functioning and developing symptoms of anxiety, adding to the growing body of evidence that there's an intrinsic biological link between our gut health and mental health.
In a new study presented at the NUTRITION 2025 conference, Georgia State University researchers presented fascinating new research into the role diet-driven obesity plays in altering brain function.
“Several studies have pointed to a link between obesity and anxiety, though it is still unclear whether obesity directly causes anxiety or if the association is influenced by societal pressures,” said Desiree Wanders, an associate professor at Georgia State University. “Our findings suggest that obesity can lead to anxiety-like behavior, possibly due to changes in both brain function and gut health.”
While the mechanisms at play are still not clearly understood, the findings suggest that while gaining weight can come with a suite of negative emotions that are very complex and personal, there's a biological trigger underpinning the change in mental health.
To better understand the link between gut, weight gain and mental health, the scientists studied weight gain in mice and studied cognitive behavioral shifts. In the study, 32 male mice six to 21 weeks of age – the equivalent of adolescence to early adulthood in humans – were split into two groups. One cohort was fed a low-fat diet, the other a high-fat one, for 15 weeks, after which their weight and fat levels were measured. But key to this research, their gut microbial make-up was also analyzed.
The animals were then challenged with a series of tasks to assess cognitive function. Not surprisingly, the mice on the high-fat diet had higher fat deposits and weight gain, and in response to the tests, these mice displayed behaviors closely aligned to anxiety symptoms in humans. In particular, they spent significantly more time "freezing" – a behavior the animals exhibit when encountering a perceived threat – than the lean mice when exposed to non-threatening cues. And brain activity analysis revealed that signaling in the obese animals' hypothalamus was markedly different to that in the brains of the lean mice.
The hypothalamus is key to regulating various metabolic functions but also plays an important role in processing fear and stress responses, which is one area of the brain implicated in anxiety disorders.
And when the scientists analyzed the animals' microbiome, they found that the two cohorts had distinctly different communities of flora.
This doesn't prove causation, as we're yet to unravel the complex ways the gut may be changing the brain and influencing other aspects of our biology like the endocrine and central nervous systems. However, the findings do support the existing evidence that there is certainly a strong link between the gut, anxiety and overall mental health.
“These findings could have important implications for both public health and personal decisions,” said Wanders. “The study highlights the potential impact of obesity on mental health, particularly in terms of anxiety. By understanding the connections between diet, brain health and gut microbiota, this research may help guide public health initiatives that focus on obesity prevention and early intervention.”
It should also be noted that experiments with mice does not, of course, mirror a real-world human experience – and not all studies on rodents translate perfectly to us – but it's cause for further investigation into how diet, weight gain, the gut's makeup and mental health is connected.
“While our findings suggest that diet plays a significant role in both physical and mental health, it is important to remember that diet is just one piece of the puzzle,” said Wanders. “Environmental factors, genetics, lifestyle choices and socioeconomic status also contribute to the risk of obesity and its associated health outcomes. Therefore, while these results are important, they should be considered in the context of a broader, multifactorial approach to understanding and addressing obesity-related cognitive impairments and mental health issues.”
The researchers are now focused on finding the potential mechanisms that underpin the gut-brain connection, and to expand their study to include female mice and animals of varying ages, to see if there are sex- and age-based differences. They'd also like to look at whether reversing the diet-induced weight gain would also relieve the anxiety symptoms and impaired cognition that the obese mice exhibited.
Wanders presented the findings at NUTRITION 2025, the annual meeting of the American Society for Nutrition, May 31–June 3 in Orlando, Florida. The research will later be published in a peer-reviewed journal.
Source: American Society for Nutrition via EurekAlert!
