Eating disorder treatment is largely ineffective. Our understanding of how to treat EDs is limited because the etiology is not well understood. This week's episode attempts to understand the "why" of EDs through an evolutionary lens. We discuss theories such as the intrasexual competition hypothesis, reductive suppression hypothesis, adapted to flee famine hypothesis, thrifty genotype hypothesis, dual intervention point model, and a psychoneuroimmunological approach. All theories explain EDs as a response to a threat and identifying this threat is critical to inform our treatment practices in recovery.