I agree with what every is saying, however, although one can not spot reduce, it is possible to increase lean muscle tissue in the areas where you tend to carry excess adipose tissue.
Unfortunately, the resistance on the reformer is not sufficient enough to elicit hypertrophy gains in your lower body as good old-fashiond resistance training would. Exercises like squats, lunges, leg curls and extensions will be effective to change your percentage of lean muscle tissue as opposed to adipose tissue.
However, in a nutshell, you will need to train your legs in such a way to give them a stimulus so that they change.
I hope this is of help.