I'm a huge orange marmalade fan! Well I'm not huge, but you get it. I still don't eat it that often because I do limit my sugar intake but it's a great treat.
As far as sugar goes, marmalade is a low glycemic index food. WAAAAY better than your standard jam/jelly. This means that eating it won't spike your insulin, so eating marmalade is really just a matter of the calories you're taking in. It doesn't have the negatives associated with most "sugar" foods. The citrus in it counteracts the standard insulin response that sugar causes; that's why Lemon Curd is even better than marmalade as far as glycemic index issues go.
So, don't go crazy with it, but you can allow yourself to enjoy it more often without worry or guilt. You can safely eat it without worrying that the body will auto-convert to fat. By virtue of it being Low GI, the body will use the sugars to resupply your muscles and cells with glycogen, instead.
