Only a semi-related post, but TheFatNurse thought this documentary on looking young on the BBC was worth some attention at 37:43:
According to this documentary, they found associations (remember the limits to associations tho!) between how old a person looked and their blood sugar levels when people were asked to judge how old they perceived a photograph of a person was. As you might guess, people with higher blood sugars looked older than what they really were. So how could this be? The documentary mentioned it has to do with the way sugar attaches to the collagen in our skin – causing the skin to become more brittle. The documentary doesn’t go deeper than that but TheFatNurse suspects they are referring to AGEs (Advance Glycation End Products) which are worth a post just by themselves in the future.