Answer:
carbs are the simplest of the macromolecules. for most instances carbs are used for a quick flash of energy meanwhile lipids store energy so it is a better and longer lasting source of fuel so if you run out of primary carbs you go to your secondary energy source- lipids. Proteins are used to replenish.
Answer:
Because carbohydrates are the most efficient form of energy. Also a lot of the food you eat will have lots of carbs. Once your body runs out of carbs it will move on to the lipids which is your fat which is still kind of efficient but not as efficient. This is how people lose weight by limiting their carbs so the body is forced to use the fat. If for some reason the body runs out of carbs and fat it will move to protein or your muscles. This is not very efficient but it will keep you alive if you haven't eaten in a long time.
Explanation:
