I am 6'1" tall. Supposedly 185lbs (84Kg) is the top end of "normal". 20Kg is what I would like to lose too.
I was once (10 years ago) 210lbs (95Kg), down from 250lbs, and I looked sickly (IMO) and so I refused to go any lower. I maintained that weight for another 3 years. I got that low using the Atkins/Low Carb approach.
All I know is at 64 years old I find it harder and harder to lose weight.
(becan, pizza and pasta don't help either)