The only widely recognised method of extending lifespan is Calorie Restriction. So why not implement it and reap the benefits!
Diabetic people should definitely give Ketogenic or LCD diet a try [after consulting your doctor]. It has helped several people. Sugar consumption should be limited to natural sources like fruits, honey etc. If in case one has to use a sweetener, we would suggest stevia or jaggery.
Low carb diet. Is it effective? why is it effective? How to prepare a Low carb diet?
One should aim to consume [twice the bodyweight in kilograms] grams amount of protein, when indulging in physical activities.