I'm pushing 40 now. Blood pressure and numbers on my blood tests are still good. Would love to lose some weight without exercising though. Knees can't take it.
It's generally a lot easier to not eat 100 calories than it is to burn them off. One thing I've found that works well, apart from just calorie counting, is finding filling low calorie foods. Bulking up a meal with cauliflower for example, or making carrot soup or just a big pile of roast carrots.
As you lose weight, it'll get easier to do some more exercise as well.
Knee strength is not an absolute. Start working on strengthening it. Have a 5 year plan. Sign up to r/progresspics on reddit. You'll be amazed at what you can do over the long term. You owe it to your body. It's all you really have.
