# Efficient Matrix Update for XDX'?

I have a matrix equation $F = X \times {D_1}{^{-1}} \times X'$, where $D_1$ is a diagonal invertible matrix.
Now, $D_1$ is updated into $D_2$ by $D_2 = D_1 + G$, where $G$ is a sparse diagonal matrix. Does anyone know if there is an efficiant way to update $F$ without having to recalculate everything?