Carbohydrates: Carbohydrates are the sugars, starches and fibres of our diet. The carbohydrate that our cells use as a primary energy source is glucose.
Fats: Fats are used as energy storage, structure, and energy expenditure in our body.
Ketones: Small molecules that the liver can make and send to the blood and brain for extra energy.
Ketosis: The state of metabolism when the body runs primarily off fats and ketones instead of carbohydrates.
Proteins: A class of big molecules that are used for structural scaffolding and machinery in our cells, but can also be used as an energy source in times of dire need (like starvation).