My partner is a motor biking mechanic who also happens to be a diabetic. For the last six months he has been on a diet that has not only lost him a stone a month but has also regulated his blood levels and his temperament. All those living with a diabetic will realise it is not always easy. Not easy losing weight not easy keeping levels correct. The diet regime is simple and effective.
Marmite on toast for breakfast and lunch or if you just feel the need (within reason). Evening meal is fish (we used sword fish and tuna steak) and vegetables eg: stir fry and brown rice. Simple and easy. He has lost six stone in six months he had to lose weight not only for himself but for his health. Now he is less grouchy and less weighty. Good luck