A lot depends on your age, and your diet and lifestyle. A normal 30 year old can easily go a day without eating, or a week on just liquids. But that assumes that you do not eat refined foods much, and have had regular exercise. These days, there are even 10 year olds so damaged, they could not handle that kind of fast. Staying away from electronics can only help (due to the emitted radiation) but the effect is so small as to be negligible for most people.
At my age, the only thing I get when I don't eat is hungry, and then I usually only notice it if I'm not busy, but as Resurrection pointed out, I am the exception, due to my diet and lifestyle.