Just want to add that although weights may be a factor for you(I don't know your circumstances), when you're riding, unless your drive ratio is nuts, you likely won't feel "heavy" while riding. Unless of course you are already heavy.

I'm a fat slob at 210lbs just under 6 feet and I have been through 2 fixed gears. My new one feels lighter yes but I don't feel like weight is a concern-I have never weighed my bike-and I only feel heavy in the wind or when I'm gassed after eating 8 double cheeseburgers for some reason.