Hi DeeDeesDay, knksmiles gave you great info.

Here's something else to think about. I'd forgotten to stock the refrigerator the other day and my peeps had eaten EVERYTHING! When I checked the game, all of the family members status was either starving, a bit weak, or weak! All of their health status's were pretty bad and I didn't have enough fruit, gel or vitamins for everyone. So I immediately bought groceries and had them prepare and eat a meal and I "sat" with them until their Fed status was full. I continued to feed them throughout the day (more than their usual 3 meals). If anyone was sick, I took care of that as well. It took nearly a full 24 hours for them to not be meal anymore (I paused the game at night because I was afraid they might die).
Back when my peeps didn't have much money
sometimes they only ate bread or whatever grocery was cheapest. If they didn't have money for the doctor, I'd wait until they gave me a clue what as wrong (coughing, clearing their throat, etc) and then give them the appropriate medicine. many times it was enough. If they constantly got sick and finally had enough money in the bank, then they'd get a doctor consult. I also didn't buy any upgrades until there was enough money to buy enough groceries.