This is what I've learned:
Don't start with "healthy" recipes you find online
My first thought when I wanted to bake a brownie that was higher in protein and lower in calories than a regular brownie was to search for "protein brownie recipes" on Google. It's not that I didn't find any. It's that most of what I found was garbage. I baked and threw out a ton of horrible tasting baked goods using other people's "healthy" recipes.
Apparently a lot of people who bake and eat 'healthy' treats aren't as picky as I am. I figure if it doesn't taste as good as a regular baked good (not necessarily "the same" but at least as decadent, if in a different way) then why bother putting it in my pie hole?
Unless you trust the source
There were a few exceptions, but mostly they were recipes from people I knew or else I'd actually eaten the results and then asked for the recipe. I consider Eggface's blog a great source of recipes, but trying random stuff off the web is to be avoided.
The person you are getting the recipe from needs to have the same health concerns as you do as well. Someone who thinks fat is evil and so replaces it with lots of high carb and high sugar ingredients isn't going to put out recipes that please me, for example. Plus, many so-called "healthy" recipes are lower in calories but they are full of artificial ingredients or sugar or sodium, all things I try to avoid.
Start with a normal recipe and substitute
Instead I have had the most success by starting with a regular recipe, full of butter and sugar and eggs, and substituting judiciously. There is definitely an art to these substitutions but over time I've come up with a few proven techniques.
Cutting down on white flour
Because I try to limit processed foods and junk carbs, I'm very interested in getting rid of the white flour. One easy way to do that is to use 100% Whole Wheat Flour. Since All-Purpose Flour is made from wheat, usually this substitution doesn't radically change the results.
However, 100% Whole Wheat Flour is more dense than All-Purpose Flour. So for every 1/2 cup of flour, I throw in an extra 1 tsp of baking powder. It works great for most recipes. I've tried just using less flour, a recommendation I've seen online but it didn't work as well for me as increasing baking powder does.
Using Protein Powder for flour
But wheat flour isn't gluten free. Plus I want to increase the protein count of my baked goods. So a lot of times what I do is put in half flour and half protein powder. I pick a flavor that matches what I'm baking because I don't have unflavored protein powder sitting around.
Lately, I've been trying 100% protein powder and no flour at all in an attempt to be gluten free. I've found, as long as you increase the baking powder like you do with 100% Whole Wheat Flour, it works great. If you use chocolate protein powder in your chocolate cake and brownie recipes, they are that much more chocolately. If you use Vanilla flavored protein powder, you can cut down on the amount of vanilla in the recipe, if you want to. But I don't -- I like having extra vanilla flavor.
Some people will cut down on the sugar (or sugar subtitute) in the recipe if they use a flavored protein powder. too. I don't usually do that and I've been happy with the results.
However, if you use chocolate protein powder in a Red Velvet cake recipe, the result is brown cake and not red cake. I learned that the hard way!
Using Nut Flours
Another way to both increase the protein content of your baked goods and make them gluten free is to use a nut flour. These are just ground nuts and there are many recipes out there that are designed to be used with those flours so no substitution is required. In particular, there are a lot of almond cake and almond pound cake recipes.
If you use nut flours in a recipe that calls for regular flour, you do have to do something about the fact that nut flours are more dense. For almond flour, most recipes have extra eggs to make them fluffy enough. More baking powder would probably work too.
You may also want to sift it so it's finer as this will give your baked goods a texture more like people are used to from a white flour recipe.
I've made a traditional almond butter cake (aka almond pound cake) and just substituted the brow sugar with Splenda Brown Sugar Blend and it turned out excellent. Oh, I also used reduced fat cream cheese for the cream cheese. I didn't substitute out the butter because it's a butter cake!
I still have some almond flour left over so I may try some different substitutions next time and see how that turns out.
Cutting down on fats
Fats are in baked goods primarily to provide moisture. So anything moist will do as a substitute.
Most people tell you to use applesauce. But applesauce is high in sugar and it's rather thin. The end result if that the baked goods are often a bit thin or chewy instead of light and fluffy. I much prefer to substitute pumpkin for fats. It gives the baked goods a better consistency, slightly increases the protein in the recipe, and, as long as you don't use more than a cup of it, you can't taste the pumpkin.
That's canned pumpkin -- like Libby's Pure Pumpkin -- and not pumpkin pie mix which has spices and sugar that will compete with the flavors and sweetness in your recipe.
There are two exceptions to this: if the recipe calls for mashed banana, I put in more banana for the oil/butter. So a recipe might say 1 cup of mashed bananas and 1/2 cup of oil or butter and I'll put in 1.5 cups of banana instead.
The other exception is an applesauce cake. Obviously, in this case more applesauce is better than pumpkin for the same reasons that more bananas works for a banana-flavored baked good.
Cutting out eggs
This is the hardest substitution to do. Eggs are supposedly in a mixture to make it fluffier and they do that. But that doesn't mean you can substitute eggs with baking powder because they also provide moisture. Plus, in my experience, eggs also help bind everything together and baking powder isn't going to do that and pumpkin might not either.
Most of the time, I just put the eggs in. I don't really care how much fat I eat and eggs are good for you in a lot of ways. But now I work with a fair number of people who don't eat eggs for religious reasons so I've been trying different substitutes.
My best results have come from using recipes that don't normally have eggs in them. One such is the so-called Whacky Cake.
The Whacky Cake recipe was created during The Depression when eggs and milk were both scarce and expensive. So this cake doesn't have them but is still very moist and delicious. Plus, it's accidentally vegan!
I made mine with sugar substitute and with whole wheat flour, but otherwise I followed the recipe as is. The sugar substitute worked fine but I was sorry about the whole wheat flour as I could taste it in the cake a little bit. But the cake had the right consistency and was very moist. I think next time I'll try a combination of all-purpose flour and chocolate protein powder and see if I like that better. (Since it tasted a bit like a piece of whole wheat bread with whole wheat flour, I'm nervous all-purpose flour will taste a bit like white bread -- hence using some protein powder instead.)
Another variation I'm thinking about trying is to put in 1/4 cup of pumpkin and 1/2 tsp of baking powder for each egg. That would replace the moisture that eggs provide as well as the fluff. Or at least that's the theory. I've yet to try it.
PB2 instead of Peanut Butter
Another substitution that I always make is to use Bell Plantation's PB2 instead of peanut butter. I find it actually bakes better than regular peanut butter and it makes a better binder for cake pops. But it has much less fat and less sugar too.
It comes in a powder and I'll either mix it up to be peanut butter and then put it in the recipe or I'll put the powder in the recipe with the dry ingredients and the water in the recipe with the wet ingredients. It depends on the effect I'm going for.
Low Fat Dairy
Another easy substitute is to use the reduced fat versions of sour cream and cream cheese when a recipe calls for them. I find that in baking, you really can't tell the difference as long as the dairy is "low fat" and not "no fat." Most "no fat" diary I find to be disgusting and for some reason it will change the consistency of your baked goods in a way that reduced fat sour cream or cream cheese will not.
Cooking with (club) soda
A final variation I've just started to try is cooking with club soda. Club soda has lots of fizz and no calories. A pretty common recipe is to buy a box of cake mix and instead of putting in the eggs, oil and water that the recipe calls for, put in an equal amount of club soda.
Some people use a can of 7-up or Sprite instead. Of course, if it's not diet, you've just added a bunch of extra sugar to your recipe and, if it's diet, you've increased the amount of artificial sweetener over and above anything you've used as a sugar substitute. Club soda is naturally no calories so that's what I use.
Except I don't make boxed cakes. (I never thought the day would ever come when I would say something like that, by the way.)
I've made a Red Velvet cake recipe using club soda and I just added up all the wet ingredients (1 egg = 1/4 c) and put in about a cup of club soda to replace them. It makes a really moist cake! The only problem is that your cake gets some weird air bubbles in it. But, if you are making cake pops, that's not a big deal because you are just going to crumble the cake anyway.
The other issue with using club soda is that, over time, your cake gets a bit rubbery. I attribute this to the lack of eggs, but who knows what really causes this. The solution is to make a small amount and/or to eat what you very quickly.
What about buttermilk
Speaking of Red Velvet cake, every once in a while I come across a recipe that calls for buttermilk. Of course, since no one in our house drinks it or bakes every day, I never have it sitting around. So what do you do? First, you can make your own. Just put 1 tsp of vinegar in a measuring cup and pour milk in until it reaches the 1 cup mark. The other alternative is to buy buttermilk, use what you need, and then freeze the rest for next time.
I've done that and it works okay. But there are only so many times you can unfreeze and refreeze it before it gets kind of gross looking. So I still end up throwing half the carton away. But it's better than throwing 3/4 of the cartoon away like I was doing before.
How can you bake and not get fat?
People ask me this a lot. There are two answers. One is that my "healthy" baked goods often have half the calories as their original recipes. The other is that I give a lot of them away.
Most of the time, I'll have a taste of what I've made and then bring the rest to work. If I find myself not being able to stop eating whatever I've made, I definitely give it away!
And take a baking break as clearly I've gone over the line from fun hobby to excuse to eat like crap.