How to lose weight just on your thighs...?

I am quite slender, I'm 5'4 and my weight yoyos between 8 and 9 stone, but even when I am at a skinnier phase, my legs hardly look any different..I have been heavily exercising for 5 years(wall-climbing and athletics) although I've stopped now, my legs weren't skinny even then. How can I make them skinnier without losing any weight from my upper body?