I've tested hunger and thirst for normal running (thank you, big pile of dirt). Weight and energy-bar level was the same for all the tests. I'm wearing my normal day and night armour. Tests was done with full energy to completely empty (character gasping for air).
Here are the results.
Hunger and thirst bars empty: 6:26 minutes to empty energy bar.
Hunger and thirst bars 3/4 full: 11:36 minutes to empty energy bar.
Hunger 3/4 full, thirst empty: 8:56 minutes to empty energy bar.
Hunger empty, thirst 3/4 full: 7:56 minutes to empty energy bar.
Screenshot of my stats and some skills while testing if any are interested: http://www.smcdk.dk/images/xsyon_test01.jpg