The inclusion of herbs, spices, lemon and lime zest will infuse fresh and interesting flavours to food negating the need to add any processed ingredients, salt or sugar, which means keeping food low fat and healthy. Home made concentrated stock will also add flavour to food. For example, I will use dried porcini to add flavour. I will soak the porcini in a small amount of water, bring it to the boil and simmer until a concentrate develops.
As for reducing fat, and liquid in a frying pan will do; it doesn't have to be oil or butter. I use vinegar or soy sauce, or if cooking with tinned tomatoes, just the juice in the tin. If I do use oil I use just a tiny bit of coconut oil. I also use an air frier, which only requires about a tsp oil.