Many areas of astrophysics rely on accurate results from stellar evolution models, in particular those of massive stars due to their importance as sources of ionizing flux and chemically enriched material. One of the biggest drivers in the evolution of massive stars is their mass loss rate, but alas this is also still one of their least well-constrained properties. In this talk, I will explore the impact of mass loss in stellar evolution models more deeply, comparing the effect of applying different mass loss rates during the main sequence of massive stars. Strikingly, the results show that the main sequence mass loss is able to affect the interior structure of a massive star down to its core, which has complex repercussions for its subsequent evolution and final fate. At the end of the talk, I will discuss the impact of these results for the applicability of stellar evolution models and address the problems and uncertainties that remain to be investigated.