My statistical model of factors that affect brevet completion time finds that a 1 percent decrease in weight results in about a 1.45 percent decrease in completion time. So suppose you and the bike weigh 280 (30 for bike) and you lose 10 pounds (3.6 percent of total) then you should be able to finish a brevet in about 5 percent less time, so a 200K that would be on the edge at 13-1/2 hours you could now complete in 12h48m with a more-comfortable margin of 42 minutes.

That's assuming the model applies to anyone other than me, anyway :-)

Nick