I am reading a paper where the author uses the following result from matrix analysis but does not explain why it is true nor provide any reference.

More specifically, let $B \in \mathbb{R}^{p\times d}$ be a semi-orthogonal matrix, i.e $B^\top B = I_d$, and $d < p$. Let $\Sigma$ and $\Delta$ denote two symmetric positive definite matrices such as $\Sigma - \Delta$ is also positive definite. What they claim is that

$$ \log \det \vert B^\top \Sigma^{-1} B \vert \leq \log \det \vert B^\top \Delta^{-1} B \vert.$$

Could someone point me in the direction of explaining why is it true?

I am thinking of using Poincaré separation theorem, which provides the bounds on the eigenvalues of the matrices on both the left and right-hand sides; however, I did not make any progress with it.