This is what medifast has to say:

"For an individual who has an exercise program in place prior to starting Medifast, we recommend cutting the intensity and duration of your exercise program in half for the first couple of weeks to allow the body to adjust to its new calorie level. As your body adjusts to this lower calorie level, you can increase time and intensity of your exercise plan. For the entire time that you are on the 5 & 1 Plan, we recommend 30 minutes of moderate exercise while limiting vigorous exercise to 45 minutes each day."

So... you CAN exercise with the 5+1 plan. But you also need to listen to your body. My health coach told me that it's okay to add a few ounces of protein if I need to, because I run long distance and weight-lift. There are also nutritionists with the program that you can talk to, also. Really important is to be extra sure you stay hydrated while exercising.

Hope this helps. I am new to the program, too, and trying to navigate through the odds and ends myself.

bumping this to hear more opinions. I want to exercise, I do it for mental health but I don't want to stall weight loss... My food should be here by Monday.
I want to lift weights for my big fat loser than before arms... That should be much of a problem, right?
Could I add a protein shake to my regimen?