When you capture a Pokemon you might notice that there is sometimes a value of XL or XS next to the weight or height of the Pokemon. Does the height or weight affect the Pokemon strength?
The simple answer here is no. People have done a lot of testing with this and the answer seems to be No. The height and weight seem to do very little when it comes to the HP of the Pokemon. This diagram will explain that CP is the only factor that affects the HP of a Pokemon.
Some have suggested that the weight will make your Pokemon deal more damage with physical attacks. The weight will also affect the speed in which you can actually attack when fighting in a gym battle, but it has not been confirmed by anyone and could merely be a coincidence.