On those calling BS, just a FWIW: steel bikes have been doing sub-20 pounds since the 1940s or earlier. Alex Singer was famously known for such, making bikes that weighed only 17 pounds! The bike I'm thinking of is featured in a coffee table book that documents French hand-made bikes. It was made for a person much smaller than myself and I suspect the frame would not hold my weight all that well. But they are indeed out there.

I used to own a bike with a fillet-brazed frame made by Terry Osell. It was set up as a two-speed, employing a Bendix two speed (blue stripe) overdrive hub, which was rather heavy. The frame was a track frame and did not have a provision for a rear brake so the hub was my solution. It weighed 17 and 1/2 pounds with pedals. I ran a carbon seatpost with that one, but that was the only carbon part on the bike.