From: Is The Only/main Reason(Way) High Gi Diet Harms Is Spiking The Insulin Level?

is the only/main reason(way) high GI diet harms is spiking the insulin level?
 
if no,then why should HIGH GI Diet be avoided?
 
also,care to explain how high GI diet may/may not make skin oily/greasy (increase sebum production)?
 
 
thanks.