Hey Midnight !
Nice to meet you!
To help a friend who is hurting, just be there and give moral support, a listening ear and a shoulder if needed. To help a friend in need of losing weight, this is not so easy. Let him know that you understand it is not easy, and that his PCP (Primary Care Physician) would be happy to set him up with a nutritionist to go over sensible diet and a regiment of eating that is just right for him and his diabetes.
Exercise is very important for weight and diabetes control. If you have time, offer to go on walks with your friend. Light exercising to start is always good, with a chance to build it into a good routine.
Sensible diet and exercise is not only good for weight control, but also for his diabetes.
God bless and good luck!