How much food should a person eat daily?

fast food = unhealthy

its all about the calories. an average man should take around 2500 and around 2000 for women
Women should eat 1500 to 2000 calories a day and men should eat 2000 to 2500 calories a day.
1 meal per meal time(not always)
As much as you are hungry. Do not confuse this with how much you want to eat, this is how much you need to eat, as in when your stomach is no longer asking for food rather than how much your brain wants to eat.

If you start listening like this, you will find yourself unable to pig out on sweets and you shouldn't put on any weight.