I've rediscovered playing.
It sounds simple, silly even. I'm an inactive guy. I love lying around, snuggling, sleeping, etc.
That's part of why I've gotten so big. You only burn so many calories while sleeping. Yes, cats sleep up to 18 hours a day. But when you spend the next 6 hours eating, there's not a whole lot of opportunity for exercise.
That's changing. I like play. I have to remind the girls that I want to play. Usually it's late at night and I know they're getting ready for bed, but that's when I get my second wind! Jess gets the laser pointer out and I chase it for about 10 or 15 seconds. That gets my heart rate up. Then we play with ribbons, strings, feathers, her hair, whatever dangles, for a good 5 to 10 minutes. I'm usually on my back, feet up, belly spread. It's not pretty, but no one look attractive when they're really working out. (Jess has threatened to take pictures of this. I've hidden the camera in the hopes she'll forget.)
Every little bit helps.