Compare percent change in loss of body weight between the OPTIFAST program and a food-based energy-deficit program

Inclusion Criteria:

• Adult males and females between 18 and 70 years
• Obese (BMI > 30 kg/m2 and 55 kg/m2)
• Non-smokers or smoking cessation > 6 months
• < 14 alcoholic beverages per week
• Willing and able to give informed consent

Exclusion Criteria:

• Active participation in any weight loss program within previous 3 months
• Weight changes of > 5% body weight within previous 3 months
• Participated in an Optifast program within prior 5 years
• Prior bariatric surgery or liposuction
• Use of any medication prescribed for weight loss in the past 3 months
• Current major disease or GI disease that is poorly controlled (Crohn's, ulcerative colitis)
• Type 1 DM
• Current ESRD
• Current COPD
• Any major or active hepatic disease requiring inpatient or outpatient treatment
• History of acute pancreatitis in the past year
• Active cancer treatment in the past 2 years other than non-malignant skin cancers
• Uncontrolled hypertension (Blood pressure 160/100 or greater)
• Hemoglobin A1c > 10%
• Recent CV event in past 6 months
• Pregnancy, childbirth, or nursing within prior 6 months
• Eating Attitudes Test (EAT-26) > 30
• Current major depressive disorder with Center for Epidemiological Studies Depression Scale-Revised (CESD-R) score > 16
• Schizophrenia, history of bipolar disorder
• Recent hospitalization for psychiatric illness in past 6 months
• Dependence on alcohol or sedative-hypnotic drugs
• Intolerance or allergy to Optifast product
• Unable to read/speak English
• Orthopedic limitation preventing participation in regular physical activity
• Untreated thyroid disease, abnormal TSH, non on stable dose of hormone replacement for hyperthyroidism
• Major surgery defined as any surgical procedure that might require prolonged convalescence or limit participation in the program in any way
• Inability to complete the 7-day run-in satisfactorily