THe release is more the protein itself, mixing whey with milk isn't slowing much down at all. THe thing to do, if you can stomach it, is to drink a large cassein protein drink at night. Its the protein itself, the type you get from milk, that takes longer to absorb. WHich overnight can provide a steadier supply of protein as your body repairs. To be fair i've in past years when buying protein supplements, not really noticed a difference from whey before sleep or going for a milk + cassein protein drink.
I guess the idea is excess protein is filtered out by kidneys so if it all absorbs in an hour, and you sleep for 8 hours somewhere between absorbing it and your body using it bits are lost to kidneys extracting it as waste. When it takes 3 hours to absorb slowly your body has hopefully used all other protein, its running low and so less is lost to waste.
AS for just starting out, honeymoon period is nice, it might be better to use it for muscle gain, do weights for a couple months, put on as much fat burning muscle as possible, then keep protein shakes going during weight loss to minimise muscle loss. One of the worst things that happens, and most demoralising is as you lose weight, you lose muscle and working out becomes tiring and hard and you feel weaker and weaker. If you can keep muscle up, with a day of compound weights training a week with a very high protein day during and day after, and a week a month doing weights with cardio the focus the rest of the time it can make all the difference.
