Every morning, before you even wake up, your body is already getting ready for the day. Cortisol surges in the early hours, nudging your blood pressure up , helping your body tap into its energy reserves, and preparing your immune system for whatever the day will bring. By the time you’re out the door, it’s helping to keep you upright and functioning. “Back in the hunter-gatherer days,” says Dr. Matthew Badgett, a primary care physician with the Cleveland Clinic, “you woke up in the morning and your body needed to produce these stress hormones to get out and walk 10 or 20 miles to get to the next fruit tree.” Cortisol is what made that possible. None of that fits the version of cortisol you’re likely to encounter online, where the hormone is blamed for everything from belly fat to brain fog to a round, puffy face, and the solution is often something sold in a dropper bottle.…