Alot of times altering a dog--male OR female--does change their bodies chemistry and they experience an increase in their wieght. You just have to take note and be very careful and aware that you are keeping their meals balanced and that they are getting the proper excercise.
We experienced it with a female AND male we recently altered, changed up their diet a bit, got their butts in motion with some extra 'fetching' and now they are back to a healthy weight.