You know whats weird about blood? You can see how much fat someone takes in. It's an entire layer in the plasma bag after the red cells have been separated. You can literally look at a bag of blood and see if that person ate a cheeseburger before they donated. The separation process is interesting too. You take several bags of blood and equalize the weights, it has to balance. So you can then put it in a centrifuge which spins them at like 3000rpm. This causes the heavier cells( the red cells) to sink to the bottom. So then the bag is two layers, heavy red cells at the bottom, and plasma (which looks like a milky water) at the top. The bag is squeezed and the plasma goes into a different bag. This is then spun again to remove platelettes from the plasma. Platelettes are what make your blood coagulate. This is why they say that one donation can save three lives.