When we are stressed, our cortisol levels shoot-up. Cortisol is basically our stress-regulating hormone; it tries to keep the body balanced even though we are experiencing stress. Some of the ways in which cortisol helps us survive during a stressful period is through immune system suppression (no time to fight invaders! We need to conserve resources to simply survive!), make glucose (gluconeogenesis) and dump it into the blood stream (must have sugar on hand for energy during this stressful time!), decrease bone formation (no time to build! We can use that calcium elsewhere!), and it redistributes fat (must preserve the central core during this stressful time!).
I'm sure you all know about belly fat, right? Well, cortisol likes to specifically store fat around the stomach/abdomen because that is where the central organs are located. If the body is super stressed out, cortisol wants these organs to be protected and preserved, and thus is directs fat build-up here.
This stress-fat relationship is important to consider when it comes to relatively thin people who still tend to have a bit of a stomach "pudge". Similarly, this comes up during weight loss stories when people just have those "last ten pounds" to lose, but have a difficult time doing so. This may be due to their stressful life and thus their cortisol "hoarding" fat in their stomach area and preventing the last bit of weight loss.
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