Hi Robert, both my siblings went to medical school, my sister is finishing up and my brother is beginning residency! To be honest medical school can be very stressful, and you do study a lot to where you may actually lose weight as well. I think it can go both ways; my sister lost a great amount of weight her first semester just because she was studying almost all the time and didn't really focus on eating and would just have light meals. However, there is a concept called stress eating as well, where you can go to unhealthy food options to relieve some of the stress you have in medical school. Just remember though that unhealthy eating is definitely an unsafe mechanism to cope with stress, and will not help at all; there are better options such as exercising, meditating and journaling as well. In terms of time commitment, even if you can go for a short run or 15 minutes of yoga, it will definitely help you stay fit both physically and mentally. I know this from my experience studying for the MCAT and in college as well because I worked three jobs and found it hard to exercise at times. When this was the case though I would resort to eating healthy, which you should always do, but make sure to maybe it give more dedication if you can't find time to move as much as you want. That way you are eating well which can help fuel your brain and body to do successfully in medical school and are staying away from unhealthy coping mechanisms!
Best of luck!