Any idea on a general rule of thumb on what the relationship is between lap times and losing weight?

Say for example, I dropped 5.45% of my weight - and went from 2750 to 2600. What percentage drop might I expect in lap times? It can't be a direct correlation, is it closer to half the weight drop percentage would equal the drop in times? For example, .5 x 5.45% = 2.72%, so on a 1:50 lap a 2.72% drop in time would be 1:47. That seems too drastic though. There are a million variables, I'm just looking for a general idea for an IT type car. I think I've heard something like .1sec roughly for every 10lbs, that would be about 1.5 seconds which might be more realistic?

Thanks.