I have a calf that's smaller than the other because of a bum knee and eventual surgery, but you can work on strengthening the weaker one with a simple exercise: stand on the ball of your foot on a step, curb, or even a threshold, and using the weaker leg only, flex down and then up on your toes, using just your body weight (which will become less effective when you lose weight
) Do three sets of 15 twice a day, and you'll notice a difference before long!