Anna brought up agave syrup in a comment on the last post, so I thought I'd put up a little mini-post so everyone can benefit from what she pointed out.
Agave syrup is made from the heart of the agave plant, which is pressed to release a juice rich in inulin. Inulin is a polymer made of fructose molecules. The inulin is then broken down either by heat or by enzymatic processing. The result is a sweet syrup that is rich in fructose.
Agave syrup is marketed as a healthy, alternative sweetener. In fact, it's probably as bad or worse than high-fructose corn syrup (HFCS). They are both a refined and processed plant extract. Both are high in fructose, with agave syrup leading HFCS (estimates of agave syrup range up to 92% fructose by calories). Finally, agave syrup is expensive and inefficient to produce.
The high fructose content gives agave syrup a low glycemic index, because fructose does not raise blood glucose. Unfortunately, as some diabetics learned the hard way, using fructose as a substitute for sucrose (cane sugar) has negative long-term effects on insulin sensitivity.
In my opinion, sweeteners come with risks and there is no free lunch. The only solution is moderation.