I've decided to stray from yogurt for a day and talk a little about another healthy substitute used in baking; applesauce. You can easily substitute unsweetened applesauce for oil in any baking recipes such as cookies, quick bread, or cake. Doing this will cut back on fat and calories quite a bit. Researchers at the Mayo Clinic (Rochester, MN) showed that the substituting 1 cup of applesauce for 1 cup of oil in a cupcake recipe led to savings of 220 g of fat and 1900 calories (9 g of fat and 80 calories per cupcake).
The research substituted 1:1 like we did with the sour cream/yogurt. The science involved with the baking process wouldn't suggest using a 1:1 substitution, which is explained well in this post. Generally you'll want to start out by substituting about half of the oil called for in the recipe - if the recipe calls for 1cup of oil, use 1/2 c. oil + 1/2 c. applesauce.
Using applesauce WILL change the taste and texture of the finished product no matter how much you use. Cookies will be a little flimsy, or won't crunch, cakes will be more dense and moist since fats aerate baked goods and allow them be light and fluffy. If you decide you like the difference, slightly increase the ratio- 1 cup oil =1/3 c. oil + 2/3c. applesauce or 1 c. oil = 1/4 c oil + 3/4 c applesauce.
If baking cakes from scratch isn't your bag, try getting one of the boxes of cake mix that just calls for oil and eggs, then substitute half of the oil for applesauce and see what you think. Also, keep in mind this will only work correctly when substituting oil or shortening in a recipe. Substitution for butter is not recommended. I'll go into more detail with butter substitution in later posts.
Note: If you don't buy unsweetened applesauce you can use the sweetened variety, but be sure to cut back on the sugar in the recipe.