I hate to admit that I do, because I recommend to others not to do the seven days a week thing. However, I do go seven days a week at times, not for weeks and weeks on end but for a couple weeks at a time on occasion. However, I am very, very sure that at least one of those days involves no lifting and just light cardio. I also have my diet down to a near perfect science, knowing exactly how much of every major vitamin and nutrient that I am getting, being very mindful of nutrient timing, being sure that I get a protein shake in immediately after the workout.
I am also supplementing with extra Vitamin E and ALA to help with free radical formation that occurs due to taxing that body at that frequency. Supplementation at this level of training becomes important. By the way why are you doing this, are you training for something specific? I also get a creatine/carbohydrate drink in immediately following workouts. The protein shake isnt just any shake either, its Optimum Nutritions Pro Blend, which contains an excellent amino acid profile as well as fast and slow digesting proteins. Doing these things helps shuttle the carbs to my muscles restoring glycogen stores and providing for the continuous availability of protein to muscles to optimize my recovery. The protein with branched chain amino acids immediately after the workout halts the catabolic processes and blunts the cortisol release while increasing testosterone release.
In essence what I'm saying is that if you are going to do that you certainly better know exactly what you are doing. You should be using software to track everything that goes into your mouth including water. You should be drinking at least a gallon to a gallon and a half of water per day, and you definitely better know what you are doing with every aspect of your program from diet to training splits to rep and set schemes, etc. Any particular detail overlooked can rapidly lead to overtraining syndrome which can have all kinds of unpleasant effects. I learned the hard way about the negative impact that it can have on immunity when I came down with a particularly bad case of pneumonia that took me a month to get over. Because I hadn't paid attention to certain key elements I ended up out of the gym for a full month.
Make sure if you do this to take an occasional very light day, and make sure you know how to structure your program with scientific precision and attention to detail, and with scientific rigor in recording everything and watching for the slightest signs of over training syndrome. One of the best ways to tell this is to take your resting heart rate first thing in the morning when you wake before you get out of bed. If the rate is ever more then 5 beats above your average you should take the day off without question and maybe a couple, at least certainly until you morning resting rate is back in line with the average baseline. In my experience this is by far one of the best objective predictors of overtraining.
Good luck with that man.