I'm not sure there is a clear answer, but, as I read it, the problems relate to a couple of things:
1 - how much you eat in general, making you overweight
2 - the amount of sugar in your blood making you more prone to a number of conditions
If you already have, say, diabetes, then I'm not sure if going sugar free will fix it ( although I bet it helps ). But, I would expect that overall, the 'damage' relates mostly to weight you will lose ( I have lost 10 kg in a month !!! ), and the lowering of risk for things like heart disease.
I think the obvious answer is, no matter what, you're better off without sugar, you can't change the past.
