This review explains how our diet affects both our gut bacteria and our mental health through the gut-brain axis, a communication system between our digestive system and brain. Mediterranean diets rich in fiber and healthy foods support beneficial bacteria and mental well-being, while Western diets high in processed foods harm gut health and increase obesity risk. Emotional eating driven by stress and depression worsens obesity, but targeted dietary interventions with prebiotics, probiotics, and fiber can help restore balance and improve both physical and mental health.