Behavioral weight loss programs for obesity can result in weight loss and health benefits. However, behavioral weight loss often stops despite efforts to continue losing weight, this can be called an involuntarily weight loss plateau. This study investigates changes in metabolism and/or the brain that contribute to the occurrence of an involuntary weight loss plateau.

Participants will be asked to enroll for 18-months. Each participant will complete 3 in-person study visits, then participate an a 6-month weight loss program delivered remotely. Some participants may be invited to complete 3 additional in-person visits. Study Visit activities include questionnaires, blood draws, brain MRIs, body measurement and dual energy x-ray absorptiometry (DXA) scan for body composition measurement, a breathing test, and biopsies of muscle and fat tissue. Each participant will be provided a fitness tracker and body weight scale to use throughout the study.

Inclusion Criteria:

• BMI 30.0 - 50.0 kg/m2
• Able to attend study intervention classes and study visits/assessments
• Independently living with access to food preparation facilities

Exclusion Criteria:

• Current smoker or regular use of nicotine containing products and/or cannabis
• Heavy alcohol use (≥2 drinks/d for females, ≥3 drinks/d for males) or drug use
• Known cognitive impairments or h/o stroke
• Type 2 diabetes (known diagnosis or by screening A1c (≥6.5%))
• Medical conditions (chronic diseases, cancer, MS) or labs limiting ability to participate
• Females: currently pregnant (or 6-months postpartum of full-term pregnancy) and/or current breastfeeding
• Use of medications with significant effects on appetite (e.g., weight loss medications, atypical antipsychotics, stimulants) and/or chronic use of anticoagulants
• History of bariatric surgery
• History of eating disorder
• Current participation in a formal weight loss program
• Prior or current participation in a research study involving weight loss
• Weight-reduced by >10% within past year
• Weight > 330 pounds (MRI limit)
• Allergy or intolerance to or unwillingness to consume study foods provided at visit
• MRI contraindication (e.g., implanted metal, claustrophobia)
• Do not have a phone compatible with activity tracker or access to videoconferencing platform that will be used for the dietary intervention or other appropriate technology needed to complete study procedures
• Any condition(s) found by the study team and confirmed with the PI(s) that make it unsafe to participate