Despite what you have heard, there is a cure to diabetes and it is all in the diet. The type 2 diabetes is usually induced by diet, but many factors can add into. Type 1, is curable, though no scumbag media wants to admit it. There is literature out there. My grandfather was diagnosed with diabetes and because he changed his diet, he does not have it anymore. He didn't even lose that much weight because he was diagnosed when he was older and had knee issues, so he wasn't that mobile. I would say for your health's sake, follow a diet that your doctor recommends and start working out (if your doctor allows it). There have been studies that show that walking 1 hour a day, without dieting, can show results in loss of weight.
Know that you should both maintain a good diet and do some sort of exercise that your doctor recommends. At least get out and walk for an hour. Studies and from my personal experience have shown that to keep weight off, and improve long-term health, your life style needs to be changed for at least 6 months. People with diabetes usually live significantly less. In Slovakia, where I am currently residing, there are a somewhat abundant number of older people who have diabetes. I have seen a lot of amputees. A lot of older guys, who are 55 or 60 (which isn't that old these days) do not have legs, teeth and have a hard time thinking or speaking. This is a result of advanced diabetes. I am trying to scare you, but this is also very real. I am not trying to hurt your feelings, but this is something very serious and I sympathize with you because I have seen it hurt a lot of people.
The main reason of type 2 diabetes is because the constant spikes in blood sugar levels. For example, if you wake up in the morning and drink a soda or two, then don't eat til lunch (when the b/s level has dropped) then when you eat, your blood sugar level will spike again. This is why people constantly rush and crash from the influx of energy from foods. This is also why people say it is best to eat smaller portions more often than fewer large portions.
When losing weight also consider losing weight in blocks. First try to lose 10 lbs, then when you have reached that goal, set another goal until you ultimately reach the goal you want. Note that it will be frustrating and will take time, but when you reach your goal you will feel like you have greatly rewarded yourself.