Figure out what you can stick to. I have always been in the same boat about workouts seeming to eat up too much time. Any time I've gained weight I have almost always preferred to cut calories until I reach a more "naturally" active state, like walking all over campus out of necessity. Recently, I've realized I would like to become someone who prioritizes working out, at least a little bit, and so I'm setting a starting goal of twice a week once I return to a University and have access to a tuition subsidized gym again! I will probably never be the type of person who will dedicate at least 30 minutes per day to working out, and if I put that pressure on myself to make it happen, I'll get stressed and not do it frequently so I won't build the habit and it just won't happen. So I'm working with myself to figure out what I can do.
In the mean time, I have figured out that I like doing some exercises that really only take one minute to do. I like starting my day doing a 1 minute wall squat, and then I work in 2-4 more 1 minute wall squats throughout the day. In the evening, depending on how much time I have, I do more body weight exercises like planks. Some days I do very few, some days I do many depending on how much time I have. Am I seeing huge weight loss? No, but within 3 days of doing three, 1 minute wall squats a day, I noticeably put on muscle mass and noticed a change in my leg shape, for the better. I am making small progress in a way that may be considered laughable to some people, but it's progress to me and that's all that matters. When I started doing planks I could only hold them for 30 seconds, I continued to stay at that level until I thought I could do 5 seconds more, and then I did 35 seconds until I thought I could do 40. I'm up to 45 seconds which isn't a big deal, but I'm proud of myself for continuing to improve. Seeing subtle changes in my body and subtle changes in time/effort improvements has inspired me to look into more body weight type exercises. Could I be doing a lot more? Absolutely, I'm not going to pretend that this is "enough" or perhaps "recommended", but it's better than nothing, and it's what I can stick to, which I think is the most important thing for me. I don't feel as if 10 minutes spaced throughout the day is a huge time commitment that will hurt my studying, and perhaps as I continue to increase these body weight type exercises, I will reach 30-45 minutes spaced throughout the day. There is no shame in starting slow or small if it is what you can do and what you will stick to. Mentally reward yourself every time you work out, and every time you see an improvement, even if it may be considered puny to others.
Note on these 1 minute exercises - I actually find them to be nice study breaks, they get my heart pumping a bit and they wake me up. I did a wall squat during every break while I was taking the MCAT!