I don't know about the tea question, but I found that tracking my blood glucose was VERY helpful in changing my diet. Helpful as in, I'm not sure I would have successfully made the shift without it.
I was inspired to get a tester after reading discussions related to Seth Robert's "Shangri-La Diet" (which was what got me reading GCBC and on the path to Paleo). I'm not diabetic and didn't discuss this with a doctor, but what I found scared the bejeezus out of me: I probably was pre-diabetic and certain high-carb foods were making my blood sugar really elevate and remain high. What an eye-opener that was!! That was why I needed to take a nap after many meals - it was the 'lite' version of a diabetic coma!! I think I went zero carb the next day...
(This is the one I got: http://www.amazon.com/FreeStyle-Lite-Glucose-Monitoring-Diabetic/dp/B001945M6S/ref=sr_1_1?ie=UTF8&qid=1305140910&sr=8-1 - it's cheap. The strips are expensive consumables but for our purposes it's not an ongoing expense). Again I highly recommend this to anyone who has 'food issues' or wants to know how a particular food is really impacting the body.
Also on the Seth Roberts forums (http://boards.sethroberts.net/) I first read about the connection between flavor and insulin: if we taste or even just smell a flavor associated with a high-carb food, out body will start to produce insulin in anticipation of consumption. As a matter of fact we need the flavor/smell as a primary trigger. There's a diet called 'Flavor Point' (?) based on that principle.
Before I go further afield, that suggests that if you associate fruit smell with sweet food it will tend to stimulate insulin release. And if you're eating ANY carbs at all about that time you'll get a stronger insulin effect then otherwise, and this increases hunger. But if you drink the tea yet avoid eating any carbs you could 'train' your body to NOT have as much of an insulin response to certain foods...
On those forums there was some incredible self-experimentation (what Seth Roberts in 'known' for). One technique was nose plugs while eating (!) which meant the body didn't "know" it was getting carbs and didn't produce insulin - i.e., if successful you could have your cake AND eat it too! Another was disassociating smells from food by eating/drinking highly flavored but zero-carb foods (like your tea), but later eating calories with as little flavor/smell as possible.
One user had great results with binge 'trigger' foods via disassociation: separate from any meals, take tiny tastes of some weakness food, extract every bit of flavor possible - then spit it out. Rinse and repeat over and over. Over time the body breaks the association because it doesn't like to be cheated into doing the extra work of producing insulin then cleaning it up.
Sorry so much info in one reply! - the Question just opens up some really interesting topics (for me). If anyone does experiment with a Blood Glucose meter I'm happy to offer my limited two bits (I've been thinking of digging it out again to test against 'paleo' foods - and booze). And some of the ideas on the SR forums might be useful to people here.