This really depends on your undergrad experience and where you end up for your MPH.
My
All Forums view on MPH programs is that you get out of it what you put into it. If you want to keep your experience light, choose easier electives,
the "lower" track option of requirements like biostatistics, and pick a more basic internship/thesis project. You should have time to study for the MCAT and will likely graduate with a high GPA.
I am doing the exact opposite of all that and find my MPH workload to be more interesting, more time consuming, and a different type of rigorous than my undergrad workload. I went to a top liberal arts school frequently described as "grueling" and fulfilled most pre-med requirements as part of my biology and education degrees (though I stopped chemistry at Organic I).