So I just went and donated blood again and durring the recovery period it occured to me that it takes quite a bit of work for your body to regenerate that lost blood volume and the actual blood cells. Regrowing that many cells seems like it would be fairly energetically intensive. So how many calories does producing all those new blood cells actually consume? Is there even a way to know that?
Yeah. “Calories in calories out” is correct in theory but it is an oversimplification. Most people burn a vastly majority of their calories “at rest” by just maintaining their body temperature.