Multiple regression tells us that on average, for every 8.5 pounds lost, people dropped an inch off their waist. (And for every 1.5 kilograms lost, people dropped a centimeter off their waist.) Every 10 pounds lost was accompanied by 1.18 inches of waistline reduction.Nov 14, 2014

http://www.decisionsciencenews.com/2014/11/14/size-will-lose-weight/#:~:text=Multiple%20regression%20tells%20us%20that,1.18%20inches%20of%20waistline%20reduction.

The picture is a bit rosier if you are losing under 55 pounds (25kg): You only have to lose 6.1 pounds to lose an inch (or 1.1 kg to lose a centimeter).