Is Intermittent Fasting Good for Women with Thyroid Disease?

Is intermittent fasting good for women with thyroid disease? It’s a question I get all the time from clients and curious followers. So let’s discuss!

Let’s start out with clarifying what exactly is intermittent fasting:

The term is thrown around in the health field a lot these days. Intermittent fasting is a popular practice, but we should take the time to clarify what intermittent fasting actually can look like. Because different people do it in different ways!

While the technical timelines can vary slightly, the general idea of intermittent fasting is to go a longer period of time without consuming food and to shorten the “eating window” in which you are allowed to consume food. 

This can look different ways:

• The 14:10 – This is when you fast for 14 hours and eat during a 10-hour window. Typically, it means you would be pushing breakfast back a few hours after waking. 
• The 16:8 – This is when you fast for 16 hours and eat during an 8-hour window. Typically, it means you would be pushing breakfast back several hours after waking.
• Fasting Mimicking, or the 5:2 – This is when calories are limited to 500 calories per day for two days a week. The other 5 days you would eat as normal. 
• Eat-Stop-Eat – This method calls for a 24-hour fast during two full days of the week. These days are not to be consecutive. 
• Alternate Day Fasting – This method is when you follow a fasting protocol, but you don’t do it every day.
• One Meal a Day – This method allows for one large meal a day or a very short eating window of four hours or less.

Clearly, there are many types of ways intermittent fasting can be carried out, but the general idea is to decrease the eating window and increase the window in which you are not consuming any nutrition. 

Why do I suggest NOT intermittent fasting, especially if you have thyroid disease?

While many men do well practicing intermittent fasting, you may be surprised to know I’m not a fan of intermittent fasting for women. After seeing its effects on countless women through my practice, I cannot recommend it. 

Why? Well, for several reasons…

Most of the research showing the benefits of intermittent fasting has been done on male subjects. There is no reliable, wide scale evidence showing a significant benefit for females:

Overwhelmingly, the studies that show any benefits of intermittent fasting were done on majority male subjects. Research is sorely lacking when it comes to female response to intermittent fasting. In fact, only 13 individual women were included at all out of seventy-one studies found in Harvard’s database for intermittent fasting. 

Additionally, no controlled studies on intermittent fasting have been done on the female population. What does this mean? There are no reliable studies that allow us to draw conclusions and valid research about how intermittent fasting affects females.

Intermittent fasting can lead to increased cortisol, reduced sex hormones and hormonal imbalance in women:

Intermittent fasting, particularly for women, can be perceived by the body as a stressor. Perceived stress due to intermittent fasting can lead to increased cortisol at baseline, which can create a cascade effect of hormonal imbalance.

Additionally, the female reproductive system is very sensitive to stress, much more so than men. During fasting the hypothalamus in women may actually turn down the production of sex hormones – particularly GnRH, which stimulates the release of FSH and LH – as the body perceives the lack of nutrient intake as stress.

Intermittent fasting can lead to impaired glucose response in women:

A study in Obesity Society found that women with a healthy body weight who attempted alternate day intermittent fasting began to present with impaired glucose response. 

We already established that intermittent fasting can lead to hormonal imbalances in women. The fact that it can also lead to impaired glucose response is unsurprising, given the strong tie between hormonal dysregulation and blood glucose dysregulation. 

What do I suggest as an alternative to intermittent fasting?

While I don’t suggest a rigorous fasting schedule, I am a proponent of a natural “fast” that is in sync with the body’s natural circadian rhythm. 

What does this look like?

I suggest ceasing to eat after dinner until breakfast time (about 12 hours) as your natural “fast.”. And I strongly suggest eating breakfast within one hour of waking. This natural 12-hour “fast” between dinner and breakfast works with the body’s natural eating-waking-sleeping rhythms to promote hormonal balance, proper detoxification, good blood sugar regulation, and recovery as well as other positive health benefits. 

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