Umbilical Hernia

I managed to get an umbilical hernia about a year and a half ago, thanks to bouncing my 45-lb. 4 year old on my tummy. It's only 2 cm, but it's sticking out more and more, and the surgeon recommend a mesh repair. OK so far.

During the past year I've managed to put on 10 lb, mostly in my belly. Now when I do situps--starting to get back in shape--I get a pronounced bulge that runs along the media alba from my sternum to my navel, as if my guts are trying to push out down the middle. I assume the fascia are weakened. What's the prognosis, and what can be done? Can diet and exercise return this to normal, or is surgery indicated?