Peanut-Butter Treat - Using Less Sugar and Less Butter
Well, from the look of things, reducing the butter and sugar will just result in a smaller recipe--that's almost all there is!

You might be able to substitute some kind of starch for some of the sugar. I wouldn't use flour, since you won't be cooking these and it would leave them tasting strongly of raw flour. I don't know what starch would work, but that's my best guess. Apart from that, I would think you could cut back on the butter a little (but not too much, or they'll become crumbly).

For my money, though, I think if you're worrying about sugar and fat, or calories in general, you need to find something else to make. These are nothing but sugar and fat (seeing as PB is mostly fat).