We show how to compute $O(\sqrt{\log n})$-approximations to SPARSEST CUT and BALANCED SEPARATOR problems in $\tilde{O}(n^2)$ time, thus improving upon the recent algorithm of Arora, Rao and Vazirani (2004). Their algorithm uses semidefinite programming and required $\tilde{O}(n^{4.5})$ time. Our algorithm relies on efficiently finding expander flows in the graph and does not solve semidefinite programs. The existence of expander flows was also established by Arora, Rao, and Vazirani.