

Find an exercise you like, and make sure to keep doing it until it’s a habit (8 weeks is usually enough for me). It raises your baseline metabolic rate, so even if you slip a bit, you can usually recover. Personally, that’s hiking or exercising while reading an audiobook which makes the time fly.
The other thing is to religiously count calories. Have an app on your phone, enter the calories every time something comes close to your mouth. Eventually, you’ll reach to eat some snack, realize you don’t know the calories, get up to figure it out from the container, and often forget about the snack while you’re up and doing something.
As always, everyone’s experience varies, but having ADHD I’ve always found the best way to get yourself to do something long term is to make it a super ingrained habit. I usually say 8 weeks is a good minimum to get it ingrained, and while I’ve had breaks, I generally find it much easier to get back to the swing of the habit if I have to take a break from it (or forget one of my exercise days).