Patient description: A 16-year-old girl came to the clinic complaining of weight gain and abnormal menstrual cycles. Her BMI was 24, but she has gained 5 kg in the past few weeks. She gets tired more frequently and does not have energy to go dancing with her friends. Her lab results were remarkable for high TSH levels (15 mU/L) and low free T4 levels (0.18 ng/dl). Her anti-TPO levels were extremely high (136 IU/ml). She was diagnosed with Hashimoto disease. She does not smoke and she is not sexually active.

Clinical trial eligibility criteria: eligible ages (years): 12.0-17.0,  Obesity Weight Gain Disordered Eating Eating Disorder Female Age between 12 and 17 years (at the start of the study) English-speaking Ability to complete study procedures, including ability to participate in a group Endorsement of at least one LOC as assessed by Eating Disorder Examination (EDE) semi structured interview  Presence of a chronic major medical illness: : renal, hepatic, gastrointestinal, endocrinologic (e.g., Cushing syndrome, hyper or hypothyroidism), hematological problems or pulmonary disorders (other than asthma not requiring continuous medication). Non-serious medical illnesses, such as seasonal allergies, will be reviewed on a case-by-case basis Presence of a documented, obesity-related medical complication that would require a more aggressive weight loss intervention approach: type 2 diabetes, hyperlipidemia, hypertension, fasting hyperglycemia, or nonalcoholic steatohepatitis Documented or self-reported current pregnancy, current breast-feeding, or recently pregnant girls (within 1 year of delivery). Because pregnancy is a state in which weight gain is expected and appropriate, pregnant individuals would not be suitable for this study. Sexually active females must be using an effective form of birth control. These methods total abstinence (no sex), oral contraceptives ("the pill"), an intrauterine device (IUD), levonogestrol implants (Norplant), or medroxyprogesterone acetate injections (Depo-provera shots). If one of these cannot be used, contraceptive foam with a condom is recommended. Should a participant in the IPT-WG group become pregnant during the ~12 weeks of the group program, she will be excluded from the group sessions. The study team will closely assist in obtaining an appropriate referral to a community mental healthcare provider, as indicated, and will request a release of information so that they may facilitate a smooth transition for the girl Current, regular use of prescription medications that affect appetite, mood, or body weight: currently prescribed SSRI's, neuroleptics, tricyclics, stimulants, or any other medication known to affect appetite, mood, or body weight. Oral contraceptive use will be permitted, provided the contraceptive has been used for at least two months before starting the prevention groups. Medication use for non-serious conditions (e.g., acne) will be considered on a case-by-case basis Current involvement in psychotherapy or a structured weight loss program Weight loss during the past two months for any reason exceeding 3% of body weight Current anorexia nervosa or bulimia nervosa as determined by documented medical history or if uncovered during K-SADS semi-structured interview. Current binge eating disorder will be permitted. Girls with anorexia or bulimia nervosa will be referred to mental health specialists for further evaluation and treatment. Individuals who need further behavioral health or medical services will be accommodated through their primary care medical home in accordance with normal clinical standard of care. This will be accomplished by direct communication with the patients' primary care physician Individuals who have major depressive disorder, psychoses, current substance or alcohol abuse, conduct disorder, as determined by Kiddie Schedule for Affective Disorders and Schizophrenia (K-SADS) semi-structured interview and as defined by outlined in the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR) or any other DSM-IV-TR psychiatric disorder that, in the opinion of the investigators, would impede competence or compliance or possibly hinder completion of the study