Timing for Weight Lifting

I lift whole body M-W-F, different exercises each day. The day inbetween is important.

It is 100% true. Try doing full body work 3x week instead M,W,F, or break up your routine into 2. You don't need to work each muscle group 4x/week, that is a bit excessive. If you break your routine into 2 you can work each muscle twice/week, and work them even harder (more sets/reps/exercises on those days, as you have less muscle groups to hit each day.

Your muscles do most of their growth, and get stronger, during the recovery period, not during the lifting. If you don't let the muscles recover prior to working them again you risk losing, or damaging, muscle.

I am a registered personal trainer and thought I would just offer some advice on this topic. They do say to have at least 24hrs, so a whole day of rest in between of training a certain muscle group. They say if your a body builder or training with really heavy weights etc to give even more time, like two days in between training. It doesnt matter that they are different exercises since you are still working the same muscle. Rest is important for muscle repair. You could do cardio on your second day or vice versa, or consider training upper body one day and lower body the second, or train chest, tris, quads, abs and calves one day and possiby back, bi's ,hamstrings, glutes and shoulders another day. There are many ways to switch it up without skipping days at the gym. But you will get greater results if you let your body get the rest it needs. In addition if you are looking to advance your training and essentially have results as opposed to just maintaining you will need to train the same muscle group at least twice a week. Hope this helps.