  We show that if $K\ge1$ is a parameter and $S$ is a finite symmetric subset
of a group containing the identity such $|S^{2n}|\le K|S^n|$ for some integer
$n\ge 2K^2$, then $|S^{3n}|\le\exp(\exp(O(K^2)))|S^n|$. Such a result was
previously known only under the stronger assumption that $|S^{2n+1}|\le
K|S^n|$. We prove similar results for locally compact groups and
vertex-transitive graphs. We indicate some results in the structure theory of
vertex-transitive graphs of polynomial growth whose hypotheses can be weakened
as a result.
