Final answer:
You will not necessarily weigh four pounds more the next morning after eating four pounds of food, because the body metabolizes and excretes part of what is consumed.
Step-by-step explanation:
No, you will not necessarily weigh four pounds more the next morning after eating four pounds of food.
When bathroom scales are used, they measure weight, which is the force exerted by gravity on the mass of your body. This weight measurement is usually displayed in kilograms, which is a unit of mass, but the primary reading is actually in newtons or pounds. If you were to eat four pounds of food, the immediate increase in your mass would indeed be four pounds. However, your body processes food through metabolism, breaking it down for energy, and expelling what's not used through waste.
Over the course of the day, even while you're asleep, your body will be digesting the food, absorbing nutrients, and excreting waste. This means that the atoms from the food you ingested will be transformed, used for energy, or expelled from your body. Because of these processes, it is unlikely that you will weigh the entire four pounds more the next day.
The scale would not read the same mass on the Earth as on the Moon due to the difference in gravity. Weight varies with gravity, but mass remains constant. On the Moon, you would weigh less because the Moon's gravity is weaker than Earth's.