If it calls for whole milk, try 2 percent and so on. Use less whole eggs. If a recipe calls for 3 eggs, try using 1 whole egg and two egg whites. Substitute artificial sweeteners for sugar. This will work in many recipes.
Variety is the spice of life.
When making low fat or low sugar desserts make sure there are plenty of good flavors. Make all your own desserts. You'll know exactly what's in them. Literally save room for dessert. Save your fat calories for dessert.