Remotely Delivered Behavioral Weight Loss Using an Ad Libitum Plant-Based Diet Versus a Balanced Calorie Deficit Diet

For the first 12-weeks of the study, participants will complete weekly web modules in which they will learn cognitive-behavioral strategies to support lifestyle modification. Participants will also receive weekly phone coaching calls for the first 12-weeks of the study, and monthly coaching calls thereafter for the remainder of the 24-week study period.

Participants will be prescribed a calorie target between 1200 and 1800 depending upon baseline weight and personal preference. Participants will be asked to monitor their dietary intake using MyFitnessPal and to submit food logs weekly. Calorie reduction content will be based primarily on the Diabetes Prevention Program protocol and adapted from existing behavioral treatment protocols. Individuals will receive general guidelines on eating a healthy diet, including reducing saturated fat, processed foods, refined sugars, and refined carbohydrates, and increasing intake of lean proteins, whole grains, and fruits and vegetables, but will be encouraged to flexibly decide which areas of their diet to modify to reduce calorie intake.

Participants will be prescribed a whole food plant-based (WFPB) low-fat vegan diet promoting intake of fruits, vegetables, starches, legumes, and whole grains. Participants will be encouraged to avoid processed foods, refined oils, and animal products (meat, fish, eggs, and dairy products), and to minimize consumption of high-fat plant-based foods. An adapted traffic-light diet chart will outline foods to eat daily, limit, and avoid. Participants will be advised to eat until satiation and not restrict energy intake. Participants will be asked to consume 50 μg vitamin B12 (methylcobalamin) daily. WFPB nutrition counseling content will be based upon existing successful programs. Each week, participants will complete a simplified dietary self-monitoring food frequency questionnaire aligned to correspond with the traffic light diet chart.