The (Impact of Weight on Quality of Life–Lite Clinical Trials Version) is a 20-item patient-reported outcome measure specifically designed for weight-management clinical trials. Key Scientific Papers (PDF Access)
The most common route is to request permission via the Obesity & Quality of Life Consulting website (often linked to Dr. Ronette Kolotkin, the original developer).
The IWQOL-Lite-CT uses a transformed into a 0 to 100 scale (higher score = better quality of life).