Inclusion Criteria:  Eating disorder diagnosis per DSM-V criteria that is characterized by binge eating (defined as loss of control of eating resulting in large amount of food consumed in a short period of time) and/or purging (e.g., vomiting, excessive exercising, laxative use) Stable medication regimen (no dose or drug changes in the past 4 weeks) Participant and parent/legal guardian (if under 18 years) are willing and able to provide informed permission/assent/consent for the study  Exclusion Criteria:  Pregnant (via UCG) Prior hypersensitivity reaction to naltrexone (e.g., anaphylaxis) Non-removable metal in the body Current naltrexone use Self-reported opioid use in the past 7 days A language barrier (e.g., non-English speaking) for the participant that precludes communication and/or ability to complete all study-related requirements.