It also goes to note that they steeped their green tea in boiling water for 5 minutes. This is too hot and too long for green tea, and will release more tannins (among other things). Besides whatever metabolic effects this would have, tannins have been shown to curb hunger short term in humans. Many animals are more sensitive to tastes, and this could have an even greater effect on the rats.
Personally I take the benefits of tea to be greater than the negative effects of these massive doses, but look forward to future studies on the subject.
"Come on, Shake off the covers of this sloth," the master said,"for sitting softly cushioned, or tucked in bed, is no way to win fame; and without it man must waste his life away, leaving traces of what he was on earth as smoke in the wind and foam upon the water. Stand up! Dominate this weariness of yours with the strength of soul that wins in every battle if it does not sink beneath the body's weight"
~Dante Alighieri, The Inferno