[rcthompson]

For some biological context, we have taste receptors in our digestive tracts identical or nearly identical to those on our tongue, only the ones in our digestive tract are not hooked directly to sensory neurons, but instead trigger endocrine signals and such. Since the receptors are identical, then anything that tastes sweet on your tongue will activate these receptors as well. If I recall my metabolism course correctly, studies have found that artificial sweeteners can trigger insulin release through these receptors in the same way as real sugar (leading to possible hypoglycemia as your body compensates for a rush of sugar that never comes).

So basically, I have no trouble believing that artificial sweeteners can have many of the same long-term health effects as excessive consumption of real sugar, since they're already known to have many of the same short-term effects, including effects on insulin regulation.