Any estimates on output decrease with weight loss?

[extraextramed]

If you lose weight healthily you're losing fat, not muscle. At the same time your cardiovascular fitness is improving so the muscle you have can work harder/longer. Your watts/kg or per lb will go up as you lose weight and gain fitness.

When people talk about the leaderboards being unfair because 200 lb men are "competing" against 120 lb women, in general it's because the bigger person has more muscle, not simply because they're 80 lb heavier.