Globally, it's estimated that around 300 million people are affected by depressive illness, and even with access to modern mental health care, long-term recovery is uncommon. Recently, there has been increasing interest in a promising intervention: the ketogenic diet. This diet restricts carbohydrate intake, promoting the breakdown of fats into circulating ketone bodies, which can act as an additional energy source for the brain, potentially reducing its reliance on glucose. While various sources of evidence suggest the potential benefits of the ketogenic diet for individuals with depression, robust clinical studies on its efficacy in depressed patients are lacking. Our goal is to conduct an eight-week, assessor-blinded, randomized controlled trial to investigate the therapeutic effects of a very low-carbohydrate, high-fat ketogenic diet compared to an active comparator diet in individuals with depression.