Also when you eat something like a dount or a pizza slice you gets fats which are like a backup energy source there is unsaturated fats which is unhealthy for you. But there are healthy fats which is called polyunsaturated and another type called monounsaturated.
So ever wondered why we eat food? Well here's the answer why! Food is fuel for our body so when we consume something like a apple or a plate of pasta we get carbs or carbohydrates that is where you get energy or fuel for your body. Also when you consume meat you get something called protein which helps you with your muscle development which affects your muscular system.
We take our food and break it down with our teeth then, the digestive system helps by turning the food into glucose or into the simplest molecules after the food got broken down. Then it gets into the blood and then, the cells use water to help regulate body temperature which happens in the mitochordria.
Ever thought about what how and what we inhale? Well when we breath in, the respiratory system helps us breath though our nose at the same time we inhale something called oxygen or a gas we need in order to live it is produced by trees.