Cortisol: The «Stress Hormone» and Its Impact on the Body

Article from the Chinese Internet

Source: 科普中国 (Kepu China) — «This Easy-to-Miss ‘Hidden Driver’ of Weight Gain is Unknown to Many People» (Excerpts) 

What is Cortisol?

Cortisol is a type of glucocorticoid secreted by the adrenal cortex. It is fundamental for maintaining the body’s normal growth, development, and metabolism. When artificially synthesized cortisol is used as a medication, it is also known as hydrocortisone.

The secretion of cortisol follows a distinct circadian rhythm. It peaks around 6-8 AM, helping you wake up and prepare for the new day, and drops in the evening, facilitating relaxation and sleep.

Cortisol also has another key characteristic: when we experience stress, the hypothalamic-pituitary-adrenal (HPA) axis becomes hyperactive, leading to increased cortisol secretion. This is why it is often referred to as the «stress hormone.» 

The Role of Cortisol: Friend or Foe?

For the human body, cortisol is not an «enemy» but a vital hormone. Its primary function is to manage survival crises and stress.

Think of it as the body’s 24/7 alarm system and emergency response commander:

• Normally (morning): It acts as your «reveille,» rising to wake you and provide energy for the day.
• During a crisis (stress): It’s the «fire chief.» When you encounter an emergency (e.g., a deadline, an argument, a near-fall), it sounds the alarm, mobilizing resources (raising blood sugar, increasing heart rate) to enable «fight or flight.»
• After an emergency: It acts as the «logistics chief,» responsible for repairing tissues and restoring calm. 

This alarm system is designed to handle short-term, life-threatening stress. Normally, cortisol helps regulate stress, break down fat, stabilize blood pressure, and even enhance focus and energy.

However, modern life often bombards us with countless pressures daily—work KPIs, deadlines, mortgages, children’s education. This keeps the body’s alarm system blaring constantly, leading to chronically high cortisol levels. Over time, the system becomes overloaded, causing a cascade of health issues. Research links consistently high cortisol to fatigue, weight gain, metabolic syndrome, loss of appetite control, muscle loss, osteoporosis, anxiety, and insomnia. 

Does Cortisol Cause Obesity?

While it’s commonly said online that «high cortisol makes you fat,» this is an oversimplification.

To use an analogy: if obesity is a «fire,» cortisol is not the «arsonist» but rather an «accelerant» that fans the flames and directs them.

The real «arsonist» (primary cause) is a long-term caloric surplus—consuming more energy than you expend. This excess energy is inevitably stored as fat.

Cortisol’s role is to make the fire burn hotter and specifically steer the fat toward your abdomen. Studies show that persistent high cortisol levels correlate with weight gain, increased appetite (especially for high-energy foods), and obesity, particularly abdominal obesity. Visceral fat can, in turn, stimulate further cortisol production, creating a vicious cycle. 

Physiological High vs. Pathological High

It’s crucial to distinguish between physiological and pathological cortisol elevation.

• Physiological High: Caused by lifestyle factors like chronic stress, poor sleep, and overwork. This can be managed through lifestyle adjustments such as improving sleep, diet, and stress management techniques. 
• Pathological High: This is a medical condition known as Cushing’s syndrome (hypercortisolism), characterized by distinct physical changes like a rounded face («moon face»), increased body hair, and easy bruising. This requires prompt medical evaluation and treatment, which may involve medication or surgery. Never self-diagnose or take supplements to «lower cortisol» without medical supervision, as this can be dangerous. 

Cortisol’s Circadian Rhythm

Cortisol levels naturally fluctuate throughout the day. Maintaining this rhythm is essential for health, allowing cortisol to be high when needed and low at night for restful sleep. Disruptions to this rhythm, often caused by late nights and shift work, can contribute to various health problems. 

Chinese Text with Vocabulary List

原文 (Original Chinese Text)

来源：科普中国 — 《这个容易长胖的“隐形推手”，很多人都不知道》（节选）

皮质醇是什么？

皮质醇由肾上腺皮质分泌的一种糖皮质激素，是维持机体正常生长发育和代谢的基础。当人工合成的皮质醇被当做药物使用时，又被叫做氢化可的松。

皮质醇的分泌有明显的昼夜节律。清晨6-8点的时候，皮质醇的分泌量达到峰值，帮助你清醒并准备好应对新的一天，到了晚上它的分泌则会降低，帮助我们放松入睡。

皮质醇还有一个特点就是：当我们感受到压力时，下丘脑垂体肾上腺轴功能亢进，就会增加皮质醇的分泌。因此，它也常被称为“压力荷尔蒙”。

皮质醇有什么作用？

对于人体来说，皮质醇并不是“坏人”，而是一种非常重要的激素，它的主要作用在于应对生存危机和压力。

你可以把它想象成身体的“24小时全天候警报系统和应急总指挥”。

• 平时（清晨）：它是你的“起床号”，每天早上它准时升高，把你从睡梦中叫醒，给你能量开始新的一天。
• 遇事时（压力）：它是“消防队长”，当你遇到紧急情况（比如deadline、吵架、差点摔倒），它立刻拉响警报，调动全身资源（升高血糖、加快心跳）让你能“战斗”或“逃跑”，这是我们的生存本能。
• 紧急事件后：它是“后勤部长”，负责修复身体组织，让身体恢复平静。

这套警报系统是为了应对短期生命危险/压力设计的。正常情况下，皮质醇激素有利于我们调节压力、分解脂肪、稳定血压等，还能激发更多能量，让注意力更集中。

但问题是，现代人却经常每天都要被无数压力或紧急事件围攻——工作KPI、deadline的稿子、房贷、孩子教育、辅导作业……这就导致我们身体的警报系统一天到晚响个不停，皮质醇分泌量长期处于高水平。总指挥官（皮质醇）也会累垮（超负荷了），于是整个身体的管理也就乱套了，就会给身体带来一系列健康问题，目前一些研究认为皮质醇过高与疲劳、体重增加、代谢综合征、食欲失控、肌肉流失、骨质疏松、焦虑、失眠等问题都有关联。

皮质醇导致肥胖？

网上常说“皮质醇高会使人发胖”，甚至把皮质醇当作肥胖的元凶，还说皮质醇高的人还很难减肥。

实际上，皮质醇本身不是肥胖元凶，但它是一个重要的“助推器”和“搅局者”。如果你把肥胖的全部责任都归咎于皮质醇就过度简化了，但忽略皮质醇的影响也是不科学的。

如果把肥胖比喻成一场“火灾”，皮质醇不是“纵火犯”，更像是“煽风点火者”。

真正的“纵火犯”（主要元凶）就是长期的热量盈余，也就是我们常说的——吃进去的能量 > 消耗掉的能量，这是导致人肥胖最根本的原因。这些多余的能量必然转化成脂肪储存在人体内。

而在这场火灾中，皮质醇的角色更像是在火堆旁的“煽风点火者”和“改变火势方向”的人。它不直接点火，但它会让火燃烧得更旺，并且特意把火苗引向你的腹部，形成腹部脂肪。

目前的研究发现，持续的高皮质醇水平与体重增加密切相关，它会增加人的食欲，让人更喜欢吃高能量的食物，容易导致肥胖，尤其是腹部肥胖。内脏脂肪还能反过来刺激人体…

词汇表 (Vocabulary List)