In general, med schools like to see that you can manage a heavy load. That load need not be solely academic. Work, significant time with extracurriculars, raising a family, dealing with significant health issues, taking an MCAT prep course--are all good and sufficient explanations for taking a smaller class load. Most important: keep the GPA high. I've read on SDN that some schools specifically want evidence that you can carry a heavy academic load and do well. If you can figure out which they are, then don't apply there.