Exercise can help moderate some of the adverse effects of an unhealthy diet on depression-like symptoms in rats, according to a recent study published inBrain Medicine.

The study, conducted in a rat model, showed that exercise helped reduce depressive and anxiety-like symptoms induced by a high-fat, high-sugar diet. The study’s findings suggest that exercise could mitigate the effects of an unhealthy diet on mood by normalizing levels of metabolic hormones, such as insulin and leptin, and attenuating the decline in certain metabolites produced by the gut microbiome.

The study’s lead author, Yvonne Nolan, professor in anatomy and neuroscience at University College Cork, said, “Our findings provide important proof-of-concept that exercise can mitigate some unhealthy diet-related mental health effects and point to specific biological pathways involved. More research is needed to confirm these effects in humans and understand the full mechanistic picture.”

The ease of access to ultra-processed foods that are high in sugar and saturated fats has led to an upsurge in obesity and other metabolic conditions. This increase in the prevalence of obesity has been compounded by the lack of physical activity and sedentary lifestyles.

Notably, the metabolic changes associated with the consumption of such a high-sugar, high-fat Western-style diet are also associated with an increased risk of mental health conditions, including depression and anxiety. A high-fat, high-sugar Western-style diet can alter pathways involving metabolic hormones, including leptin and insulin, as well as the composition and metabolism of the gut microbiome.

Specifically, the consumption of ultraprocessed foods is associated with reduced gut microbiome diversity and the production of microbial metabolites that increase inflammation and alter brain function. These diet-induced changes in the gut microbiome and metabolic hormones have been shown to contribute to the effects of obesity on mental health.

In contrast, studies conducted in rodents have demonstrated that exercise can reduce depressive and anxiety-like symptoms while improving cognition. Exercise is associated with increased gut microbiome diversity and the production of microbial metabolites, such as short-chain fatty acids, which, in turn, are associated with a protective effect on mental health.

However, it is not known whether exercise can help attenuate or reduce the negative effects of a high-sugar, high-fat modern Western diet on mental health. The present study, conducted in young adult male rats, examined whether exercise could attenuate the effects of a high-sugar, high-fat cafeteria diet on mental health and metabolic changes.