I can't say how long it will last (hopefully a long time!), but exercise/diet/weightloss has certainly worked for me.
At the beginning (2+ years ago), I was: very overweight, with a BMI in the high 30's - fasting 7+, A1c around 8 - blurred eyesight and tired all the time - high blood pressure (165/95) - failed one OGTT, but passed another. Really, just on the tipping point between very high pre-diabetic and runaway diabetes.
Since then, I've: exercised frequently (moderate walking) - cut out most refined carbs - was on Metformin for a brief period then Glucobay (which is really great stuff) also for a short period.
Today, : lost well over 100lbs, bringing my BMI down to 24, waistline down to 34" (from 48") fasting this morning was 4.3, last A1c was 4.7, BP 126/71 and have twice passed an informal OGTT.
From my trusty OneTouch meter's software, my two week averages:
fasting:4.6
2hrs after lunch: 4.4
before dinner: 4.7
2hrs after dinner: 4.8 (OK, confession time, had burgers in buns with fries twice this month)
night: 4.4
(one month averages a little higher, I had a glitch caused by a temporary anaemic episode)
So, do I have diabetes any more? if I were to walk into a GPs office (and they did not know my history), they'd look at my present numbers and say that I have no excess risks and that I do not have diabetes, nor am I even prediabetic.
Obviously, if I went back to being a slob, I have no doubt that diabetes would be back with a vengeance!
I'm of the opinion that early intervention with Metformin as a good idea, since it helps get you down to non-damaging levels much faster, only then try and come off it when you are able. There are reports that the earlier you start it, the longer you are able to avoid other - more side-effect prone - drugs like insulin and those that force the pancreas to produce more insulin.
I still have a supply of Glucobay/Acarbose - taken with the occasional high carbohydrate meal (Christmas/Birthday/vacation &c.) it prevents damagingly high spikes, effectively turning a 'bad' meal into a low GI one - to an extent.
I still test reasonably frequently (more than I ought/need to, I think - it is easy to get a bit paranoid and anxious about BG - trying to wean myself off it). I'm subject to occasional anaemia and that pushes my BG up a bit, until I take supplements that brings it down again.
I've slacked-off on the exercise a bit (but still do it 3 or 4 times per week) but my weight remains stable at around 35% less than I started from. If anything, there is still a very slight downward trend in my blood glucose averages.
So, long rambing reply to your question boils down to - yes, I think you can.
This is the time when you have the best chance to improve your long term outcome - go for it.
Hope this helps.
mark