Depending on how heavy you were lifting, you should be able to get back to your old strength by dropping the weight significantly and working back up to it over a few months (maybe do something like Starting Strength).
I have been working back up to it that way, but consistently plateauing at about 20% below my previous peaks.
I do plan on changing my diet once I'm at a place I'm happy with to be a bit more friendly towards weightlifting goals.