In young adults with major depressive disorder receiving standard counseling or medication, a 10–12 week well-formulated ketogenic diet was associated with a 69% reduction in self-reported depressive symptoms (PHQ-9) and a 71% reduction in clinician-rated symptoms (HRSD), alongside improvements in global well-being, body fat mass, and cognitive processing speed.

When the body runs on fat instead of sugar, it produces ketones that enter the brain and trigger the growth of new brain connections while calming down inflammation. This helps the brain function better, lifts mood, and improves thinking speed. At the same time, losing body fat reduces a hormone that was overstimulating brain inflammation, further improving mood and mental clarity.