Effectiveness of the Optifast Program Compared With a Reduced-energy Food Based Diet Plan on Body Weight

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