Obesity is associated with increased pain with knee osteoarthritis and increase progression of knee osteoarthritis while weight loss intervention has been shown to reduce pain and requirement of total knee replacement. In this study, the investigators will assess using diet modification with exercise, and metformin, a common, safe, diabetes mellitus medication that has been in use for 70 years to achieve better weight control to reduce knee pain. This helps the investigators to understand whether the combined treatment can reduce joint pain, reduce body weight and improve symptoms and requirement of total knee replacement.