Specifically, a reduction in good bacteria resulting from a diet rich in saturated fats is believed to influence the processes responsible for producing GABA and glutamate.

GABA and glutamate also play a significant role in regulating appetite and food intake. Decreased GABA or elevated glutamate levels may affect inhibitory control and could contribute to unhealthy food choices and overeating.

The Diet and Mental Health Connection
Andreas Michaelides, chief of psychology at Noom, told The Epoch Times in an email, “GABA (Gamma-Aminobutyric Acid) is an inhibitory neurotransmitter, meaning it reduces neuronal excitability and helps calm the brain. When GABA levels are stable and adequate, they help reduce anxious thoughts by calming the brain

https://www.zerohedge.com/medical/new-study-explores-how-food-choices-shape-mental-health