What do you mean by refined carbs? Does it include bread, pasta, potatoes, etc? Because I don't think those are bad for you because they don't cause blood sugar levels to rise as quickly as stuff like HFCS and sugar (but I could be wrong).
Just because they aren't as quick as HFCS doesn't mean they aren't bad for you. A bagel at breakfast has over 100 grams of refined carbs that become glucose in your blood within minutes of eating it. Tell me that isn't bad for you. Eat one every day and you might just get diabetes...
If I pull a potato out of my backyard garden, bake it, and then chow down, what part of that has been refined? There's as much fiber in a russet potato than there is in a half-cup of brown rice.
It might be that the cause of diabetes is glucose level spikes and therefore insulin spikes; the video that was posted here last month with the Robert Lustig from UCSF talking suggested it actually something other than insulin that contributed insulin-resistance -- free fatty acids precipitated by the liver. It's not as simple as saying this thing that has spikey behavior is going to become ignored by the body if it keeps spiking. Things that seem analogous aren't always, as much as it would make knowing good from bad so much easier to distinguish.
I won't tell you it's bad for you, but I'll tell you with a pretty damn high amount of certainty something else: both and I and you don't know it is bad for you.
Might there be a risk? Sure. But then we've spent the last thirty years believing something else, saturated fats, were more of a risk than they now appear to be. It might be possible that we are leaping too quickly from possibly correlative to sufficiently causal yet again.
There's a lot in common between the saturated fats craze of the preceding few decades, and the fervor of our new dietary crusades today. I'm not convinced that we've learned a damn thing from that experience, and thus worry we are destining ourselves to looking back on this craze the same way in 30 years. Biochemistry and metabolism just aren't that simple; making it artificially simple doesn't do crap.
Potato in particular is bad because it is a concentrated source of very high GI starch,
Are you sure about that? My experience is that if I haven't eaten enough and eat bread and then go running it doesn't help much, whereas if I eat sweets or something else with a lot of sugar it helps almost immediately.
Tables 1 and 2 will give you a quick summary.
fructose is a sugar with a propensity for glycation
If you want to follow a low glycemic index diet, it's much more important to avoid potatoes, white bread, white flour and rice than HFCS