• fat distribution [ Time Frame: 0, 6 mo ] [ Designated as safety issue: No ]
• insulin sensitivity [ Time Frame: 0, 3,6,12,18 mo ] [ Designated as safety issue: No ]
• perceived stress [ Time Frame: 0, 3,6,12,18 mo ] [ Designated as safety issue: No ]
• mood [ Time Frame: 0, 3,6,12,18 mo ] [ Designated as safety issue: No ]
• stress hormones [ Time Frame: 0, 6, 12 mo ] [ Designated as safety issue: No ]
• autonomic nervous system function [ Time Frame: 0, 3,6,12 ] [ Designated as safety issue: No ]
• adipocyte activity [ Time Frame: 0, 6 mo ] [ Designated as safety issue: No ]
• influenza vaccine response [ Time Frame: 3 months ] [ Designated as safety issue: No ]

The purpose of this study is to compare two approaches to a diet and exercise-based weight loss program.

The high prevalence of obesity and its medical consequences make it one of the most important public health issues in the United States today. Few interventions have been consistently successful at reducing obesity. This trial will test an intervention program that lasts 22 weeks, with 16 evening sessions and one weekend day. Participants will be randomized to one of two arms. Both arms will receive diet and exercise intervention elements. The study aims for gradual weight loss, with a calorie target that will maintain ideal body weight, rather than a more calorie restricted diet. The exercise component is based around increasing walking. The arms will compare methods for producing long-lasting behavior change.

• Experimental: SHINE A
  Intervention: Behavioral: SHINE
• Active Comparator: SHINE B
  Intervention: Behavioral: SHINE

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
• 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)