Hmmm. I hope that makes alot of something: there are tons of calories in that recipe!
The flour you pretty much have to leave as is. You can increase the fiber by altering the white-whole wheat ratio in favor of whole wheat, but that won't really change the calories much. I've found that if you want to add more whole wheat to baking recipes, it's advisable to use the whole wheat pastry flour, as it is lighter.
An obvious place to start making substitutions is with the fat. I often sub apple sauce for butter or oil. You can do an equal exchange on those two. You can also sub flax seed meal for fat in baking recipes (at a 3:1 ratio, I think), but flax seed meal, while very healthy, is still quite calorific.
Honey...well, you could just halve it, and have a less sweet product. Or you could sub half the honey for some splenda if you wanted. Personally, I hate the taste of splenda, but lots of people are fine with it.
The other big calorie punch here is the walnuts. At least 785 cals!!! I'd be inclined to eliminate those or cut waaaaayyyy down on them unless this recipe is going to make 40 servings or something.
One thing I've found is that when you sub out the fat, or add extra fiber to a recipe, you do compromise texture. That's the main thing. No whole wheat apple sauce concoction is going to be as light as a white flour/butter or oil concoction. That's just the nature of the beast. But, if you can live with that, it does make it possible to eat treats that might otherwise be outside your calorie budget.