Blog Diets Fasting Intermittent Fasting Cortisol: Should You fast?

Intermittent Fasting Cortisol: Should You fast?

Do intermittent fasting cortisol levels go haywire with you? Are you feeling anxious about a lack of results from your fasting program? Do you have a standoff with your bathroom scale? If any one of these is true for you, you must discover the connection between cortisol and fasting. 

High intermittent fasting cortisol levels may be to blame for your stagnant results. That said, they may also indicate that intermittent fasting (IF) isn’t the right weight management program for your needs. We would like to help you understand the connection and learn what to do about it. 

Why Fasting Increases Cortisol

Intermittent fasting cortisol levels may spike because of the following reasons: 

  • Not eating enough in eating windows (12)
  • Not managing stress in the first 2-4 weeks of fasting (10)
  • Already having higher-than-normal cortisol levels (4)
  • Hormonal conditions, like insulin resistance (8, 3, 9)
  • Being a woman (11, 15)

None of these causes say much, so let’s dig deeper. 

Does Intermittent Fasting Raise Cortisol Levels?

Does fasting increase cortisol? It may raise cortisol when other factors contribute to your natural daily stress, like trouble at work, financial issues, hormonal issues, or relationship problems. Here’s a jaw-dropper: being a woman can also make it spike more. Let’s discover the facts.

Can Not Eating Enough Raise Cortisol?

Scientists from the University of California studied how calorie restriction and counting affected cortisol levels (12). Calorie restriction elevated cortisol levels in women, and counting calories caused a spike in perceived stress. This suggests that eating too little could raise cortisol levels. 

Intermittent Fasting Cortisol Study

The John B. Pierce Laboratory reviewed studies linking higher cortisol to fasting and very low-calorie diets (16). The meta-analysis reviews various studies to see similar patterns, making it more dependable than looking at a single result. 

intermittent fasting cortisol  

Unfortunately, fasting increased serum cortisol. The results suggest fasting or severe calorie restriction activate the hypothalamus-pituitary-adrenal (HPA) axis responsible for sending you into a stressful state. 

However, the good news is that cortisol levels returned to baseline after several weeks (16). The initial shock to your body activates the HPA axis that protects you from the effects of starvation. However, it seems to later subside. 

See also
An 18-Hour Fast May Be Just What Your Body Needs for Optimal Health

Question, how long would it take to pass the initial state of shock on your body? Johns Hopkins Medicine suggests it may take 2-4 weeks for your body to adapt to the added stress (10). In that time, you may experience headaches, moodiness, or hunger during this period. 

Furthermore, you should start slow and progress into intermittent fasting schedules to avoid the stress-fasting loop. Some people may also have too many daily stressors to place this added strain on their internal systems. It’s a good idea to talk to your healthcare provider before starting a fasting regimen. Let’s understand the danger of fasting cortisol. 

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The Cortisol Fasting Danger

The studies already show that fasting may cause an increase in cortisol. However, what would that mean for you? Should you be aware of any dangers that may follow cortisol spikes if you’re already in a state of elevated stress daily? Let’s understand cortisol first. 

What Is Cortisol?

The Cleveland Clinic says cortisol is a glucocorticoid (steroid) hormone responsible for various functions in your body (4). It regulates your body’s stress response, suppresses inflammation, and regulates blood pressure, glucose, and the sleep-wake cycle. Furthermore, cortisol manages how your body metabolizes fat, protein, and carbs for energy. 

What Happens When Cortisol Is Too High? 

Your HPA axis regulates how much cortisol floods your body at any time, but any perceived threat to your well-being will activate the stress response. The hypothalamus releases corticotropin-releasing hormone (CRH) when cortisol is necessary (4). 

The pituitary gland then releases adrenocorticotropic hormone (ACTH), which signals the adrenal glands above your kidneys to produce more cortisol. Your liver also quickly produces more glucose for energy, and your body goes into a stressful or an alert state. 

See also
Intermittent Fasting 14/10 vs 16/8: Differences, Similarities and How To Make The Best Choice

The Cleveland Clinic says some side effects of chronically high cortisol levels include (4):

  • Elevated blood pressure
  • Higher blood glucose, which can lead to type 2 diabetes
  • Weight gain
  • Muscle weakness in upper arms and thighs
  • Bone weakness and fractures

Intermittent Fasting and Cortisol Effects on Hormones

Fasting and cortisol could affect hormones negatively and positively. Knowing the hormonal pros and cons can help determine whether fasting is right for you. The disadvantages may be more prevalent among those with too much or unmanaged daily stress. 

Human-Growth Hormone (HGH)

Researchers at the University of Virginia Medical School found that fasting could encourage the body to produce more HGH (7). HGH is responsible for sustaining healthy bone density and muscle mass. However, it naturally starts dropping after 30, but you could stress your body more by forcing it to produce more HGH after 30. 

On one hand, higher HGH may improve bone density and muscle mass. On the other hand, the Cleveland Clinic warns that higher-than-normal HGH levels may cause acromegaly (8). Acromegaly may lead to enlarged organs, thicker bones, and swollen extremities or facial features. It may also elevate blood pressure or deregulate glucose and insulin levels. 

Consider how fasting affects you personally. If your HGH levels are too high, don’t fast. If they’re normal, you can enjoy the benefits of HGH for your bones and muscles. Talk to your healthcare provider for individualized advice.

intermittent fasting cortisol  

Insulin and Glucose

You can fast if you can manage stress, but having too much fasting cortisol and daily stress may negatively affect insulin levels. The Childhood Obesity Research Center found that consistently high cortisol levels may decrease insulin sensitivity and increase glucose production (3). 

However, the center underlined that a cortisol reduction may reduce the risks. On the other hand, newer research by Chinese scientists suggested that intermittent fasting may improve insulin resistance (5). Check with your doctor about your risks if you’re diabetic or insulin-resistant. 

Fasting May Affect Women’s Hormones More

The Cleveland Clinic says women’s estrogen and progesterone hormones are more sensitive to fasting and perceived stress (11). Fasting stresses your body and your reproductive cycle. Your reproductive hormones constantly rise and fall through your cycles.

See also
Intermittent Fasting for Men: Optimizing Male Wellness


Women of reproductive age may be better off fasting at certain points in their cycle and not others. . Also, start with shorter 12-hour fasts and progressively build your way up to 16-hour fasts. 

Moreover, raised cortisol can further threaten your reproductive goals if you wish to become a parent. Michigan researchers found higher cortisol urine levels after ovulation was associated with reduced progestin (15). Stress may also negatively impact implantation and your ability to conceive.  

Read more: How Your Fasting Windows Can Make Or Break Your Intermittent Fasting Experience

Can Intermittent Fasting Lower Cortisol in Some People?

Probably not, but rising cortisol may benefit you in certain situations. You may need more HGH, not live with insulin resistance, and be mentally well enough to embrace the benefits of higher cortisol levels. The Fordham University Department of Psychology found slight cortisol elevations beneficial (13). Appropriately rising stress levels may make you more alert and reduce fatigue. 

How Do I Know Whether I Should Fast or Not?

Ask yourself whether you don’t have higher risks for the complications associated with higher fasting cortisol. As a recap, the Business Insider suggests watching out for these warning signs that fasting may cause too much stress (1):

  • You have orthorexia or constantly worry about what to eat next. Anyone with a past or current eating disorder should never fast. 
  • You self-shame or feel guilty after breaking a fast too early, which may indicate disordered eating patterns. 
  • You feel unusually overwhelmed, stressed, or anxious. 
  • You start feeling antisocial or isolate yourself.
  • You get bouts of “hanger” – hunger and anger combined. 
  • Fasting affects your sleep.
  • You battle to focus and feel like you aren’t alert anymore.
  • You skip a period or lose your hair.

How Do I Keep My Cortisol Low While Fasting?

Managing cortisol while fasting requires knowing when not to fast and some stress management tools. 

See also
10 Intermittent Fasting Mistakes People Make And How To Avoid Them

Check Your Intermittent Fasting Cortisol Level!

A normal fasting cortisol level range is 10-20 micrograms per deciliter (mcg/dl) in the morning or 3-10 mcg/dl in the afternoon or evening, although this can vary between labs (4). Cortisol naturally peaks in your saliva, urine, and blood earlier in the day but subsides as the day progresses. 

If there is a concern about your cortisol levels, they can be tested by a healthcare provider (4). Discuss the potential of your fasting with your healthcare provider.. 

Intermittent Fasting 16/8 Cortisol Management Tips

Managing stress during 16/8 or any intermittent fasting schedule will help you benefit from the weight loss trend. First, ensure that you don’t meet the requirements for anyone who shouldn’t fast. Then, use these tips from Cornell Health and Alarabiya Ramadan fasting experts to manage stress while fasting (17, 14): 

  • Stay hydrated enough between and during fasts to prevent unnecessary stress on your body from dehydration (17). Drink eight glasses of water daily to prevent caffeinated dehydration. 
  • Eat a well-balanced diet in eating windows to sustain your body’s stress levels during fasts. Eat meals with lean protein, whole grains, fruits, vegetables, and healthy fats. 
  • Sleep for at least six hours each night and exercise to reduce stress while fasting. Low-intensity exercise can improve your mood (14).
  • Engage in soothing activities during fasts, and don’t forget about self-care. Meditation, warm baths, or pet play can soothe stress (14).  
  • Trust your body and break your fast if you feel overwhelmed. You must find what works for you; sometimes, fasting isn’t the answer. 

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For more information on intermittent fasting:


Can Not Eating Enough Raise Cortisol?

Eating too little may spike cortisol levels. Researchers from the University of California found that calorie restriction could raise cortisol levels to stress individuals more when eating less (12). Even counting calories could make individuals perceive themselves as more stressed. 

See also
Carve Out A Fasting Schedule To Meet Your Fitness Goals

What Are the Symptoms of High Cortisol Levels?

The Cleveland Clinic suggests chronically high cortisol levels may cause facial and abdominal weight gain, excess fat between the shoulders, and purple belly stretch marks (4). You may experience muscle weakness in your arms and thighs and have bouts of hypertension. Furthermore, high blood glucose levels, weak bones, and excessive hair growth are signs.

Does Intermittent Fasting Reset Hormones?

Intermittent fasting isn’t a magical hormone reset, as it has the pros and cons you saw in this article. It can help with some hormone changes but work against others. Let’s look at another study on hormone changes with fasting. Scientists from Chicago examined how fasting influenced hormones among overweight men and women (6). 

Sadly, fasting may decrease testosterone in men. Men with low testosterone levels possibly shouldn’t fast. On the other hand, premenopausal women had higher levels of sex hormone-binding globulin (SHBG), a protein that binds to estrogen and progesterone. The results show that fasting may help women with polycystic ovary syndrome (PCOS) to regulate cycles for improved fertility. Fasting impacts hormones differently for everyone, but it’s no magic reset. 

Does Coffee Increase Cortisol?

Sadly, coffee raises cortisol because of the caffeine stimulant. Researchers from Oklahoma found that caffeine elevates cortisol levels further during stressful states and at rest (2). If stressed, consider reducing coffee and caffeine while fasting. 

The Bottom Line

Intermittent fasting cortisol can increase, leaving you feeling worse or losing no weight. Respect the signs enough to know when you shouldn’t fast, and use the tips to manage your stress while fasting if it’s safe to continue. Either way, focus on your wellness beyond weight management, which means you must be aware of how your cortisol levels and stress affect you. 


This article is intended for general informational purposes only and does not address individual circumstances. It is not a substitute for professional advice or help and should not be relied on to make decisions of any kind. Any action you take upon the information presented in this article is strictly at your own risk and responsibility!


  1. 8 Signs Your Intermittent Fasting Diet Has Become Unsafe or Unhealthy (2019,
  2. Caffeine Stimulation of Cortisol Secretion Across the Waking Hours in Relation to Caffeine Intake Levels (2008,
  3. Cortisol Is Negatively Associated with Insulin Sensitivity in Overweight Latino Youth (2010,
  4. Cortisol: What It Is, Function, Symptoms, and Levels (2021,
  5. Effect of Intermittent Fasting Diet on Glucose and Lipid Metabolism and Insulin Resistance in Patients with Impaired Glucose and Lipid Metabolism: A Systematic Review and Meta-Analysis (2022,
  6. Effect of Intermittent Fasting on Reproductive Hormone Levels in Females and Males: A Review of Human Trials (2022,
  7. Fasting Enhances Growth Hormone Secretion and Amplifies the Complex Rhythms of Growth Hormone Secretion in Man (1988,
  8. (HGH) Human Growth Hormone: What It Is, Benefits, and Side Effects (2022, 
  9. Insulin Resistance: What It Is, Causes, Symptoms, and Treatment (2021, 
  10. Intermittent Fasting: What It Is, and How Does It Work? (n.d., 
  11. Is Intermittent Fasting Healthy for Women? (2023, 
  12. Low-Calorie Dieting Increases Cortisol (2010,
  13. Positive Upshots of Cortisol in Everyday Life (2016,
  14. Ramadan 2023: Experts Advise Teens on Managing Stress Amid Fasting and Exams (2023,
  15. Stress and Female Reproductive Function: A Study of Daily Variations in Cortisol, Gonadotrophins, and Gonadal Steroids in a Rural Mayan Population (2004,
  16. Systematic Review and Meta-Analysis Reveals Acutely Elevated Plasma Cortisol Following Fasting But Not Less Severe Calorie Restriction (2016,
  17. Tips for Healthy Ramadan Fasting – Cornell Health (n.d.,
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