• Body weight
• Risk factors for heart disease (e.g., lipid profiles)
• Blood sugar

This study compares two types of diet interventions: a low carbohydrate ketogenic diet (Atkins) and a low-fat diet combined with a medication (Orlistat).

Overweight and obesity are increasingly prevalent in the veteran population as well as the general public. For patients with obesity-associated illnesses, there are few effective treatment options available after failed attempts at diet and exercise, even though weight loss has been shown to alleviate these conditions. The purpose of this study is to compare the tolerability, safety, and efficacy of a low-carbohydrate ketogenic diet (Atkins) with a combination of a low-fat diet and Orlistat. The outcomes examined over a 48 week duration will include body weight, risk factors for heart disease (e.g., lipid profiles), and blood sugar. This is a randomized, parallel-intervention trial. Subjects (n=150) will be recruited from the Durham VAMC Ambulatory Care Clinics. All patients receive one of the two intensive weight loss interventions.

• Obesity
• Diabetes Mellitus

• Behavioral: Low carbohydrate ketogenic diet
• Drug: Orlistat plus a low-fat diet

Inclusion Criteria:

• Participants must have a VA medical center primary care provider;
• Failed first line diet and exercise recommendations;
• In stable health by screening physical and lab tests;
• Agrees to make regular visits per study protocol;
• Has access to telephone;
• Body mass index (BMI) > or = 27 with obesity-related illness OR BMI > or = 30 with no risk factors;
• No contraindications to Orlistat;
• Not pregnant or breast-feeding;
• No serious mental health illness such as dementia or schizophrenia;
• No use of a weight loss therapy in the month prior to screening.