There has been much recent interest in applying AdS/CFT methods to condensed matter physics, thereby mapping strongly coupled phenomena to mildly interacting gravitational systems. Here we will focus on the precise embedding of these holographic models into string theory, by means of consistent Kaluza-Klein truncations. We will review recent progress in understanding how, associated to supergravity backgrounds involving M2 and D3 branes in a planar configuration, massive Kaluza-Klein modes can, against the standard lore, be retained consistently. We will further show that, associated to M5-branes wrapping cycles of special holonomy manifolds, consistent truncations of D=11 supergravity also exist. We will discuss an specific example where the truncated theory is D=4 N=2 matter-coupled supergravity and show that this effective theory is amenable to further top-down AdS/CMT investigations. In particular, by-passing previous no-go statements, we are able to find a Lifshitz-invariant M-theory background.