In that case, you should get on taking the MCAT right away and make that your priority. There is only pathway to get the skills necessary to be a physician, and that's to go to medical school, so that's your #1 barrier to being a physician scientist.
There are a bunch of pathways to get the research skills to get started as a physician scientist. Extra year of research in medical school. Research track residency or fellowship. MD/PhD. An MD/PhD program is a very rigorous way to get research training, which is great, but it isn't very tailored to what you want or need because you're getting all this training based on some presumption about what you will be doing in the future. Generally speaking, research experience closer to when you begin your career is more valuable, because it can be more tailored to what you are actually doing, and there is no loss from being out of the field for however long. Any research you do before starting medical school, and especially an MD/PhD program will be useful only from a theoretical standpoint because it could be 12 years or more until you are actually a researcher. (Of course, I get it, these things build on themselves. More experience before a PhD can theoretically make it smoother, etc)
The real problem is time here. Right now 1-2 years seems like no big deal, right? If you spend 3 years doing research, then matriculate in an MD/PhD program, get out in a pretty smooth 4 year PhD, do a 2 year fast track IM residency + 4 year fast track fellowship, we are talking about 17 years of training, starting now. Meaning you can think about getting a junior faculty position in 2032. Just let that wash over you a little bit.
I'd recommend spending 1 year getting your MCAT in order, potentially doing one of these research programs while applying. Depending on where you go to school, you can approach people at your own or nearby universities about potential research opportunities. Alternatively, you could apply for these summer fellowships (SURF, etc), and then try to weasel that into a full year of working in a lab. A lot of labs have glorified techs that have undergrad level education and work on their own pseudo-independent projects, which is what you want. With a decent year, you will be a good MSTP applicant. Then, you can try to decide between applying to both MD or MD/PhD programs (or perhaps both, that way if your research experience is what limits you, then you can just head right into medical school). If MD only you can maybe take a year off between M2 and M3 and go to NIH for a research year, because a fair number of people do that. A few schools offer 5 year MD/MS type programs (like Cleveland Clinic). While not as robust as a PhD, you can spend the time you save getting extra experience at the end.
Don't get me wrong, I think MSTPs are a really interesting pathway, and that's what I did myself. However, I started straight out of college when I was 21. I was the first person out of my class to finish my PhD, in just under 4 years, did a 5 year residency and now am in a 2 year fellowship. Each year before you start just prolongs that goal. Each step of the way has been fun, but I'm now 35 and still in training (it gets old).
