Just saw my doc today and he said to lose 30 pounds because my blood pressure is too high. So I just ordered 30 days worth of high protein meal replacement shakes. I'm going to detox, the last time I lost 25 pounds in one month. I do go visit the gym once in a full moon, but I don't make my own shakes. It just cost me about $200 for 30 days supply!
Your kidneys will be fine unless you are overweight, and or have some type of pre-existing condition with your kidneys. I was a gym rat but since I got married and had 2 kids I don't go to the gym as much anymore. It's bad for your health, too much eye candy to get you into trouble.
Drink plenty of water and don't overdue the supplements! People who do have problems like Kidney Stones and Liver Damage from drinking too much protein shakes or taking supplements already have pre-existing liver conditions; otherwise it has been proven that protein shakes won't damage your liver or kidneys.
Don't take my word for it, I'm no MD but studied the subject matter in great depths and detail. Been there and done that too, shakes are better for you than eating all this man made crap, well the good tasting crap btw is bad for your kidneys. I still eat it even I know it puts on a few pounds. Got to enjoy life while your still breathing, no need to wait for tomorrow, for it may never come!
I was going to be a PT aka personal trainer, got my training and schooling done; nobody wants to pay someone in this economy to train them. Besides, I still have my nutrition certificate and PT Cert! I love too eat hence the losing of 30 pounds.