Food is very important for the body and without food the body cannot function properly because that's how God design it.
We need food to survive,we need food for our body to be strong and healthy and also lack of the right food has side effects on the body.
No matter how strong or physical you think you are, you can't survive without food.
Food gives the body vital energy.
Can someone survive without food for two day?
According to experts, the body can survive without food for seven days and can survive without water for only three days maximum.
So based on this fact,yes you can survive without food for two days and still be fine but the thing is your body will be very weak during this period and there are something you can't do because of lack of strength.
Religious folks who engaged in fasting stay for days without eating which is OK but afterwards, they do eat something.
So if someone is an ulcer patients it's not advisable to stay without food for two days,it's very dangerous for them.