In 2015, Cake Of The Week celebrated a Low Fat January. With these recipes, low fat does not equate to low taste. Search "Low Fat" to find recipes that were featured.
It's really incredibly easy to reduce the calorie count/fat content of your baked goods. I like to try and eat healthily so, though I don't tend to mention it in my posts, I always use low fat spread in my cooking. Low fat spread doesn't noticeably change the way your cake comes out; all butters and spreads have slightly different flavours so your cakes might have a slightly different taste (i.e. less rich), but the quality will not change.
A discovery that I made recently (see my Healthy Brownies for more details) is that mayonnaise can be used to replace butter or spread and cuts the fat content and the calories by a notable amount. You might want to watch the salt though, and increase the sugar by 10% to counteract the saltiness that it brings to the table.
Stevia is an all-natural sweetener that can be calorie-free, and is three times as sweet as cane sugar. It tastes just like sugar when used in baking and has a wonderful toffee aroma, but the baking guidelines state that you need to reduce the temperature by 10C and increase baking time by about 10 mins. For more about my experience with Truvia, a brand of stevia sweetener, take a look at the post on Chocolate Cupcakes With Buttercream Icing.
If you're still not satisfied, Picklee has a page full of substitutions for baking healthier food, e.g. swapping butter for avocado. Check it out!