Randomized Controlled Clinical Trial of Weight Loss Programs in Obese Persons

Inclusion Criteria: * Age 18+ years old * BMI \> 30-45 * Waist circumference \> 102 cm (men) or \> 88 cm (women) * Live in San Francisco Bay Area and able to attend more than 16 classes and up to 12 assessment visits in San Francisco over an 18 month period Exclusion Criteria: * Inability to provide informed consent * Age \< 18 * A substance abuse, mental health, or medical condition that, in the opinion of investigators, will make it difficult for the potential participant to participate in the group intervention * Type I or II Diabetes or fasting glucose ≥ 126 mg/dl or hemoglobin A1c ≥ 6.5; those with HbA1c between 6-6.5% may complete an OGTT to rule out diabetes (glucose \<200 mg/dl) * Use of systemic (oral or IV) corticosteroids in the 6 months prior to enrollment or severe autoimmune disorders or other conditions (e.g. rheumatoid arthritis, lupus), that are likely to require these medications * Use of immunosuppressive or immunomodulating drugs or chronic or acute conditions that would require the use of such medications * A history of known coronary artery disease (CAD), or typical or atypical anginal chest pain requires a letter from the participant's physician that he or she has been adequately evaluated and that a moderate exercise program is appropriate * Non English speaker * Pregnant or planning to get pregnant in the next 12 months, breastfeeding or less than 6 months post-partum * Initiation of new class of psychiatric medications in past 2 months * Currently on a specific weight loss diet * For influenza vaccine administration: a prior allergic reaction to the influenza vaccine or eggs. These participants can be included in the trial but will be excluded from participation in influenza vaccination. * Active bulimia or strong history of bulimia * Current use of weight loss medications or supplements such as amphetamine-based drugs that are believed to have some effect on weight * History of or planned weight loss surgery * Untreated hypothyroidism: TSH \> 4mU/mL (or the upper limit of normal reference defined by the lab doing the assay)