Tara Swart is a neuroscientist, Faculty at MIT Sloan, and former MD. She is author of USA award winner and UK best seller The Source: The Secrets of the Universe, the Science of the Brain, which has translations in 38 languages. She hosts the podcast Reinvent yourself with Dr. Tara which has peaked at No 2 in the USA and No 1 in the UK in Life Sciences on Apple Podcasts. Tara is passionate about applying neuroscience to wellness and beauty.

“The feeling of stress — whether it's physical, emotional, mental or spiritual — always correlates with the hormone cortisol. Cortisol is part of the 24-hour circadian rhythm, which is your sleep-wake cycle that correlates to the dark-light cycle outside. There's a normal range, depending on your age and gender, for what your cortisol should be bouncing between throughout that 24-hour period. Just before dawn, when the body kickstarts the waking up process, we get the largest spike of cortisol that we should get during the 24-hour period. That helps us wake up, jump out of bed, and start the day. Then we should go back to this normal range. When we're chronically stressed, that level of cortisol creeps up towards the top of that range, and can even become higher and kind of stay there the whole 24 hours.

There are special receptors in our brain that are always monitoring the level of cortisol that's going around in our blood. When the brain senses that level is high for a sustained period of time, it goes into survival mode and thinks, ‘What could be an imminent threat to my survival?’ Even though in the modern world there are usually more psychological threats to our survival, the brain defaults to the wiring that it had when we lived in the cave. It immediately starts to think of things like saber tooth tigers or hypothermia or starvation.

“Even though in the modern world there are usually more psychological threats to our survival, the brain defaults to the wiring that it had when we lived in the cave.”

One of the first mechanisms is that we feel more hungry. It’s such a small thing, but it’s important to start realizing that hunger could be a symptom of stress over a few weeks or months, because we tend to respond to it unless we're extremely disciplined. We may notice that we put on more fat in our abdominal area because that's a survival mechanism. If you were being hunted down by another tribe or if food was really scarce, you would need to store fat in your abdominal area so that you could burn that and survive for longer. Certainly during the pandemic, we saw a lot of people not only put on weight, but in a distribution that was more central than all over your body.

Because cortisol is part of the sleep wake cycle, any type of sleep disturbance is quite an obvious sign of stress. So whether that's difficulty falling asleep, waking up in the middle of the night, or waking up earlier than you need to, not feeling refreshed and unable to go back to sleep.

Physical manifestations of stress are usually in your gut or your skin. Your skin is the physical boundary of your body, but it's also the psychological boundary of your body. So any boundary transgressions — people taking advantage of you emotionally, physically, or financially — can really show up in your skin. Because of the gut-brain axis, if you're stressed, it really does tend to show up in your gut like IBS, leaky gut, diarrhea, constipation, food cravings, weight loss or weight gain.

The other thing is that you're just more irritable to things that happen in daily life, like the kids screaming or the boss being demanding or the partner being unreasonable. When your cortisol levels are high, your ability to maintain a threshold of not reacting badly becomes lower.”

Want more? This is an excerpt from a longer convo with Dr. Tara Swart — listen or watch here!

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