by Dr. Will Cole

The benefits of intermittent fasting are abuzz in the wellness world with research supporting its ability to decrease inflammation, heal the gut, and increase cellular repair. As a functional medicine practitioner it’s a therapeutic tool that I recommend on a regular basis for many of my patients.

While limiting food intake for a period of time can do wonders for your health, there are some concerns regarding the potential side effects it could have on hormonal health, especially for those with thyroid problems, adrenal fatigue or other hormone imbalances.

So let’s dive deep into the hormone-fasting connection to help determine if this could be a good healing tool for you:

1. Fat storing and hunger hormones: (leptin, insulin, + ghrelin)

Intermittent fasting takes center stage in its role in improving hunger, metabolism, and blood sugar affecting hormones. When patients come in with blood sugar problems I like to recommend IF due to its proven ability to increase metabolism and lower insulin resistance. If you have a blood sugar problem and want to try fasting it’s key to work with your doctor who can monitor you and slowing increase your length of fasting as your glucose stabilizes. Leptin resistance, another hormonal resistance pattern which leads to weight gain and weight-loss resistance, has also been shown to improve with IF.

And if you think fasting would make you more hungry, think again. Intermittent fasting has been shown to positively affect the hunger hormone ghrelin which can directly improve brain dopamine levels. This is the perfect example of the reality of the gut-brain axis connection.

2. Estrogen and progesterone

Your brain and ovaries communicate through the brain-ovary axis or hypothalamic-pituitary-gonadal (HPG) axis. Your brain releases hormones to your ovaries to signal them to release estrogen and progesterone. If your HPG axis isn’t working well it can affect your overall health and lead to problems with fertility.

When it comes to intermittent fasting, women are usually more sensitive than men. This is due to the fact that women have more kisspeptin, which creates greater sensitivity to fasting. If not done properly, IF can cause women to mess up their cycle and throw off their hormones. While more research needs to be done it would make sense to logically conclude that this hormonal shift could affect metabolism and fertility too.

Now all this to say since every person is different, this doesn’t mean you can never try intermittent fasting. You may just have to go at it with a different approach. Crescendo fasting can be a great way to gradually introduce fasting into your routine.

  • Fast two nonconsecutive days a week (such as Sunday and Thursday).
  • Only do light exercise on fasting days.
  • Fast between 12 to 16 hours.
  • After a minimum of two weeks add one more day of fasting to your routine.
  • During this time I recommend adding around 6 grams of branched-chain amino-acid supplements (BCAAs), which come in powder and capsule form. These can help improve the positive impact of fasting and help take the edge off.

2. Adrenal hormones (cortisol):

Cortisol is your body’s main stress hormone and is released by your adrenal glands which sit right on top of your kidneys. When your brain-adrenal (HPA) axis is thrown off it can lead to an imbalance in cortisol. This high and low rollercoaster ends up leading to adrenal fatigue. I’ve found that people with dysfunctions with their circadian rhythm don’t handle intermittent fasting well. However, trying a slow beginner intermittent fasting protocol or the crescendo fasting could be ok with someone monitoring your progress.

3. Thyroid hormones (T3 and T4):

Your thyroid is queen of all hormones affecting every single cell in your body. No other hormone has that power. If your thyroid hormones are not functioning optimally, then nothing is. There are many different types of thyroid problems all of which can be effected differently by intermittent fasting. Therefore, I recommend working with a functional medicine practitioner who can work with your specific health case.

If you suspect that you might have a hormone problem check out my guide on the topic to get some more answers to your lingering questions. If you know you are clear to start look no further to start your intermittent fasting journey:


  • The 8-6 window plan: One simple way to IF is to just eat between 8 am and 6pm. This allows for a long fasting period within a reasonable timeframe.
  • The 12-6 window plan: I personally do this plan during my workweek. This is the same as the last plan but extends the fast a couple more hours into lunchtime. I fill my morning with big cups of water and antioxidant-rich matcha tea.


  • Modified 2-day plan: Eat clean for five days and then restrict calorie intake to 700 on any two other days. Limited calorie intake can have similar effects as full fasting.
  • The 5-2 plan: Eat clean for five days and fully fast for two nonconsecutive days a week.


  • Every-other-day plan: Fast fully every other day. While intense, it can be very effective for some people.

If you want to learn more about your own health case please check out our free health evaluation. We offer in person as well as phone and webcam consultations for people across the country and around the world.

Photo: Stocksy


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