When I eat more to the ketogenic side of low carb--60-70 grams of protein, around 20 grams of carbs--I find I naturally lower my sweetener intake. Part of it's that a packet of splenda equals an ounce of low carb veggies for carbs, a poor trade. But diet pop starts tasting too sweet to me. Eat pretty much the same calories and carbs, but with a bit more protein, a bit less fat--and I'm more likely to want sweetener in my coffee, and more of it. Also I'll have to try to keep cheese and peanuts out of the house, for fear of binging on them. So even in just this one person, there's a varied response to sweeteners.

I guess this sort of biases me towards thinking that sweeteners are only conditionally bad. You can design a study to make them look harmless, you can design a study to make them look harmful. But maybe the question isn't whether sweeteners are harmful or helpful--but under what conditions they are harmful, and under what conditions helpful. Dr's. Westman, Bernstein, Atkins, etc., have helped a lot of people without banning sweeteners--but I don't discount those who report better results once they took them out of the diet, either.