You were probably eating more because you were upset at the diagnosis.
There is one sure-fire way to lose weight without following a rigid diet. Well, for me at least.
As low-carb as possible!!! The bad news: NO bread, NO cereal, NO fruit (not right now). NO fruit juices. Absolutely NO sugar, cakes, biscuits or anything sweet.
Do not buy convenience or junk foods. NO pizza or burgers!
The good news: Have eggs and bacon for breakfast, with a slice of crackerbread, butter, and tea with artificial sweetener. Or have 2 crackerbreads with butter and finely grated cheese. You can also have a glass of tomato juice. (I thin mine slightly with water, and add Worcestershire sauce and a few drops Tabasco, which I like). You can have cold cuts like ham on crackerbread as well. All a bit boring, but worth it.
For lunch, get those sachets of tuna and eat that with your low-carb crackerbread. Think of other ways to eat protein and vegetables (also avocados). Have "light" or "lite" Cup of Soup.
Don't eat between meals, and if that was a habit -- that your jaws must move -- get some artifcially-sweetened chewing gum.
Then have a nice evening meal of the usual: whatever meats or fish you cook, two freshly-cooked veggies, a large salad with a nice salad dressing, 2 small baby potatoes ...
Yes, one does get hungry sometimes. Go do something to take your mind off food. Within 20 mins. the hunger will subside.
Oh yes, very NB: get moving!!! Go for a walk at least 3 times a week, for 30 mins. If you are unfit, you won't walk very far to start with. But one gets fit very quickly. If you can't walk alone in your area, you could walk up and down steps near your home, or join a gym and walk on the treadmill. However, fresh air and a brisk walk is probably nicest!
I lost 10 kg within 2 - 3 months by eating proteins, vegetables, salads. I did not touch bread at that stage (and yes, I missed it badly!) The crackerbread I mention has only 4.5 g of carbs per slice.
Tuna with French dressing or mayo was, and still is, a godsend. And I have wine with dinner, as I've always done. Seems quite good for the blood glucose!