depends on your starting weight/height etc. and how much you run per week, how fast, etc. lots of variables.
but if you run consistently each week for a good amount of time/speed, you should be seeing results in anywhere between 3-4 weeks. even sooner if you are changing your food lifestyle.

It all depends, if you are eating healthy and running and exercising, dailey at a significant amount than i would say you should see a small result after a week, and after about 2 1/2 weeks, you should deffinatly notice a difference in your size.
hope this helps,
BDS