Hunger is a physiological phenomenon...something which is biologically triggered which tells you "it's time to eat". Starvation is a condition in which the body is not being nourished so as to cause a multiple of maladies and conditions, including death. However, when you say, "I'm starved!" or "I'm starving!" it's just to indicate that you are extremely hungry. Might be a good a idea to have a good breakfast! :-)

starving is a more severe condition than hungry yet, they both have similar meanings.

'starving' is more hungry than just 'hungry': hungry -> starving -> dead