Lose weight, run faster

Every runner has his own reason for running, Roughly you can divide it into two categories
1: Running for the exercise burning calories, being healthy, being outside instead of in the gym, etc.
2: Running for the performance: Further and Faster
Most runners know you’ll get reason one for free if you start working on number 2.
On one of the blogs on complete running I found this table which also shows that the reverse is true. If you loose some weight you will gain speed. According to research 2 seconds on a mile:

Unfortunately no link is present to the research that resulted in this table. There should be some optimum minimum weight. However I would not go for this optimum. Most top runners look like a running skeleton wrapped in a skin and nothing less. For me, and I think for most recreational runners, this is a bit over the top. So I stick to my current weight and try to gain these second with a little more trainingeffort!
Added on 21st of june: I found a nice calculator that gives an indication of the effect of weight on your performance. The results are in line with those of the table above.