Is Intermittent Fasting Destroying Your Hormones?

I am a big advocate for intermittent fasting, but only if it’s executed correctly and based on bio-individuality. If this isn’t taken into account, it can do more harm than good and actually be dangerous for some health conditions. 

It is important to consider gender, as women are more at risk when intermittent fasting. Body type also needs to be thought about, as intermittent fasting is great for the Kapha body type, but Vatas need to be careful. Check this post to find out about what body type/Dosha you are if you haven’t identified it yet!

If you don’t consider these factors and bio-individuality, you run the risk of destroying your hormones. 


Intermittent fasting is where you go for extended periods of time without food. The window where you don’t eat must be minimum 12 hours, but is usually longer than the period of time when you are eating. 

Unless you have a health issue where intermittent fasting could be detrimental to your health, such as hypothyroidism, I encourage people to fast for at least 12 hours every night (i.e. finishing your dinner by 7pm and having breakfast at 7am). This gives the body time to properly digest food and gives the gut rest and recovery time, amongst lots of other associated benefits. 


Biologically, women’s bodies are built for reproducing. If the body goes for extended periods without food, the body will assume that this is not a good time for reproduction, as a result your estrogen and progesterone levels are affected. 

Estrogen is responsible for more than the reproductive system, it manages metabolism, heavily influences weight loss (especially around the mid-section), regulates mood, contributes to cognitive function, influences energy and stress levels. 

Disrupting the estrogen balance will negatively impact these essential physiological processes. Therefore, doing intermittent fasting in the wrong way can result in weight gain, poor cardiovascular health, decreased muscle mass (and therefore, decreased metabolism), impaired cognitive function, blood sugar dysregulation, fatigue and infertility. 

Additionally, hormones work in ratios of each other. If one hormone level becomes imbalanced, this will trigger other hormone imbalances. So, if estrogen is thrown out of whack, cortisol and thyroid hormones will take a hit too. This could result in anxiety, insomnia, sugar cravings, brain fog, weight gain, dry skin and hair, irregular menstrual cycle and depression. 


Mistake 1: 16/8 Method

The 16/8 method has become very popular and people who follow this eating plan fast for 16 hours a day and consume all of their calories during the remaining 8 hours. It may work for some, especially if you’re a Pitta body type with strong digestion. However, getting all of your calories and nutrients for the day in a space of 6-8 hours means overtaxing your digestive system.

Mistake 2: Skipping Breakfast

A 12h overnight fast does not require you to skip meals but this might not be the case in longer methods (i.e. 16/10 and 18/6). People practicing longer fasts for weight-loss reasons generally skip breakfast and while this might work in the short-term, it will certainly backfire in the long-term by lowering your metabolism. 

Remember, a person with a “low” (or slow) metabolism will burn fewer calories at rest and during activity and therefore has to eat less to avoid graining weight.

How does skipping breakfast lower metabolism?

Well, when you skip breakfast, the body feels more stressed from not eating causing a spike in cortisol. Once you’re in the “fight or flight”, the body thinks that you’re being chased by a wild animal or are lacking resources and it begins to lower thyroid hormones so you can survive for longer with fewer calories. Guess what? Your metabolism is controlled by your thyroid! Read about The Relationship Between Cortisol And Belly Fat here.


You don’t need to miss out on the benefits of intermittent fasting, but you do need to take into account bio-individuality. Taking at-home functional labs will give you a good idea of this. For example, if your thyroid is already on the lower side from a functional medicine standpoint, fasting for too long will just add more fuel to the fire. 

If you’re skipping breakfast, you may want to rethink which meal you’re sacrificing. It has been proven scientifically that you will burn more calories when skipping dinner compared with skipping breakfast.1 This makes sense when you think about humans’ circadian clock because metabolism and blood sugar control are much stronger in the morning than they are in the evening and at night. 

However, burning less calories is just a side effect, and you should focus on the more serious detrimental effects of skipping breakfast such as blood sugar spikes and increased body fat. Read my blog post on Why You Shouldn’t Skip Breakfast here.  

I also recommend that women don’t do intense workouts, like HIIT, on days that they are doing extended fasting. HIIT workouts can actually trigger the stress response, causing cortisol to spike, and we have already spoken about how careful you need to be with this hormone for weight loss and overall health. Not eating can put stress on the body, so you don’t want to double up the stress levels. 

I’m a big proponent of doing longer fasts certain times in the year to boost mitochondria and cellular clean-up for different diseases. This is why people in our community complete the 7 Day Reset every quarter because it incorporates long intermittent fasting periods in a very specific and effective way.

I generally recommend following the 21 Day Reset if you’ve never done a functional medicine detox before, and then maintaining with a 7 Day Reset every season. That is what I’ve been doing for years for overall wellness, weight-loss and anti-ageing benefits!




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