Intermittent Fasting – What It Really Does To Your Hormones.

So you know, I’ve been fasting.  Truthfully you may not actually know but I did post a picture on my socials sharing of how I had been intermittent fasting for the past eight weeks and I can safely say my body is loving me crazy for it.  You, my favourite people had a LOT of questions and so in true NK style I knew I needed to pin down a date with my keyboard and tap this out for you, so here we are.

Intermittent Fasting in a nutshell is going for select periods of time without food.  I have written about it here before and dived right in, it’s worth taking a read.  Maybe if you had asked me just three short years ago my thoughts on fasting, I would have told you it’s a big NO for your hormones.  Truthfully though, we are always learning and hit fast forward I’m here today to say, I’m a big fan.  Not only have I been trialling it myself, but I’ve also been doing this with my patients for some time too.

With this in mind, I want to answer the questions that have hit my inbox over the past few days – to really help you decide if this is something for you or not.

Why fast?

For all of time, it’s safe to say we haven’t had food at our beck and call.  Fasting therefore is a natural process – something we’ve maybe dived into throughout intense periods (i.e. Lent) or in times of famine and we’ve survived to date!

Due to the shear availability and convenience of forever available food, we’ve somewhat disconnected from our body’s signs and signals.  We can eat whenever, whatever, taking us further away from our innate state of being.  Fasting allows for regeneration and recovery that is essential for health and allows us to somewhat tap back into the body’s natural groove and to really be able to listen to what your body is telling you – without the noise of over consumption.


What happens when you fast?

Most interestingly, fasting steers the body towards using fat rather than sugar as a fuel source.  Many foods in our modern diet that are consumed in great quantities (i.e. grains) are quickly converted to glucose and dished out to be used as energy. This takes priority over fuel from fat stores and should there be glucose left unused it is then stored as glycogen in the liver, our muscles or our body fat. Each time we eat, we top up glucose.  It’s only once we dip into the fasting state that we use these reserves in our body fat.

You might find it odd that fasting actually influences the hormones that regulate hunger (insulin and leptin). Happy and balanced insulin and leptin means balanced hunger, fat storage and correct signalling of what we actually need nutritionally.

How do you fast?

Research is still working out what’s what, however fasting for as little as a couple of days a week will still have positive effects. For patients I tend to look at their personal situation, however the most common ways to fast include;

+ 5:2 – that is 5 days of normal eating and 2 days of limited intake.  I think this works well for those who don’t have small children.

+ Crescendo fasting – this is fasting 2 – 3 non consecutive days per week.  If you have obvious hormone imbalance, this may be the pick of the bunch and a great place to start.  In this instance you would fast 12 – 16 hours (the majority being overnight).

My favourite is 16 hours overnight.  I generally advocate this for my patients because it’s the easiest rather than needing to go 2 days of the week with low calorie intake (500 calories for women 600 for men).  You might choose to do as little as 3 days of the week or more.  I would encourage you to play around with the idea to find what works best for you.  The way I look at this isn’t to focus on the 16 hours without food but focus on the 8 hours that you are eating and make it count.

+ Lee Holmes also advocates for ‘Up Day, Down Day’ fasting.  She suggests this works for those who don’t have a regular schedule meaning that every other day you limit your food intake the 8 hour window.

Is it bad for your metabolism?

In the long term, there is no evidence to suggest that it has a negative impact on your metabolism, in fact quite the contrary.  The first few weeks of fasting can be a little tricky as you find your groove, and this is where you can feel everything from hungry to jittery, however over the course of 12 months, research shows that insulin sensitivity improves. That is, your cells are more sensitive to insulin immediately after periods of fasting which means you should find your sugar levels are happier in general.  This aids in lowering inflammation and improves insulin signalling pathways which is good news for many, including women with PCOS and those with a family history of diabetes.

Can anybody fast?

There are a few ‘camps’ that may avoid fasting for various reasons;

+ teenage girls – as their hormones find their groove.  It’s not completely incorrect but since we are all different I’d advocate for calling on the assistance of a health care professional or trying on more gentle fasting like up day-down day.  We can also get confused between changing hormones and symptoms that mimic issues like PCOS.  It can be beneficial to hold out.

+ expecting and lactating mothers – for obvious reasons.  Growing tiny humans and feeding them is a full time job.  You need your reserves.

+ depending on your health state and condition if you have a known illness, it would be wise to recruit a doctor to support you – fasting as we’ve seen for example, in the case of diabetes may be wonderful but having the eyes of somebody else on your health is always my best suggestion.

What do you eat?

Food!  It’s just limited to whatever time frame you choose.  Some people choose to eat as they please on the down time others continue to eat a whole food diet.  For me, since fasting I’ve cut out all processed sugars, grains and diary.  It’s been a wonderful thing to observe my body and how I feel.

For women trying to balance hormones it is crucial that you continue to eat plenty of good quality fats and protein.  Fasting can have a negative impact on your hormone health if you starve yourself – that’s not our aim with intermittent fasting.  You’ll know if this is the case because you might find your periods go missing or become irregular.  This would be a sure sign you are overdoing it.

There’s a simple solution, include good quality fats like avocado, nuts, seeds, butter, oily fish and my favourite – eggs, frequently. As well as quality meats, fish and of course organic chicken.

I do find I am way more thirsty whilst I am in a fasting period and drink loads of water as my body asks for it.

What are the physical benefits?

So we’ve established better hormone balance which is mostly why I suggest this for women in the clinic, but what comes with fasting is steering the body towards it’s healthy weight, more energy, deeper sleep, balanced sugar levels and better brain function all of which are simply a result of the body not being clouded by two things – the wrong foods and too much of it.  When the body can operate from this more natural state, the benefits are quickly noticed.

As always, it all comes back to how we can lead your body to a more homeostatic state of being by removing the stressors that exist from our modern lifestyle.  It may be that we’ve never thought about excess food consumption being a stress on the body (add that to the pile alongside other internal stress, external stress factors like your environment as well as your emotional stress!!)  We all know I’m mad for ironing out stress creases.  Resonating – find out more here.

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I’d recommend going slowly at first and really allowing your body to find its own rhythm when it comes to intermittent fasting.  We are all different and I’m keen to open the conversation up to fasting and diet.  Have you done it?  Did you like it?  Be sure to take time to leave your thoughts in the comment section below.


  • December 14, 2017 By Emily 10:38 am

    I’ve been fasting once a week for about 5 months and I’m feeling so much better for it. Thanks for the blog Nat – it explains intermittent fasting so well!

    • December 14, 2017 By Nat Kringoudis 2:26 pm

      You’re so very welcome – I’m glad you love it!

  • December 14, 2017 By Nikita 11:15 am

    I have a question Nat! So, you’d recommend 16 hour gap for a healthy female? If I work out every morning at 6am where would you suggest I do my fast from? Would it be quite important to continue to have breakfast at 7/7:30am.

    • December 14, 2017 By Nat Kringoudis 2:27 pm

      It’s really up to you to try a few things on. I’d probably suggest only doing this 2 or 3 days a week, maybe on non workout days? That said I fast and train and it’s fine.

      • December 24, 2017 By Briana 5:17 pm

        I have been doing 5:2 for a while and find on my fast days I have more energy and can lift heavier at the gym… it takes about 3 months to get used to it though so in those first few months perhaps not train on the fast days.

        • December 28, 2017 By Nat Kringoudis 1:14 pm

          It really is the best!!

      • April 25, 2018 By Anne 4:46 am

        I exercise daily and am fasting during this time frame. I believe that exercising during fasting allows for quicker weight loss as your energy is now being drawn from your fat stores. Please correct me if I am wrong.

  • December 14, 2017 By Rose S 5:59 pm

    Hi Nat, great post! I have been doing a 16 hour fast daily and I am feeling good but I have noticed that my fasting blood sugar is great before lunch and dinner but high in the morning. Do you think continuing to do IF this way will help get this down. I’m not diabetic or pre-diabetic, thanks Rose

    • December 14, 2017 By Nat Kringoudis 11:27 pm

      I think it’s ok! Tricky without knowing the full details but so long as you feel ok?

  • December 14, 2017 By Nicole 11:56 pm

    I watched your live post but my connection kept cutting out. So you may of answered this already. Can you drink herbal tea while in the fasting period?

    • December 17, 2017 By Nat Kringoudis 9:20 am

      Yes you may – I actually have coffee (black) but you can of course drink tea, coffee and water.

  • January 2, 2018 By Samantha 9:11 am

    I have been trying intermittent fasting 16:8 also and loving it! I feel so much less bloated! It was recommended to me to try as I have PCOS, I am really interested to see what did does after a longer period of time. Due to my hormone imbalances and PCOS I was told to stop drinking coffee back in 2016 however I have been now told I can have bulletproof coffee (with ghee and coconut oil) while fasting. What is your take on having this one coffee a day for hormones/PCOS and is this blended bulletproof coffee ok while fasting?

    • January 18, 2018 By Nat Kringoudis 11:24 pm

      I think having bulletproof coffee is fine and I would advocate exactly what you are doing for my patients. PCOS is treatable and IF is perfect for it!

      • January 22, 2018 By Samantha 3:15 pm

        Thanks Nat! I am honestly feeling great doing IF during the week, then weekend I do normal. Do you still fit your 3 meals a day in when fasting? I am finding I am only needing lunch (at time of breaking the fast) then some sort of snack/bone broth in the afternoon then dinner. Its all a bit of trial and error really haha!

        • January 22, 2018 By Nat Kringoudis 10:16 pm

          Yes I think it’s about trial and error. Most days I only eat lunch and dinner too.

  • January 8, 2018 By Emily 1:37 pm

    Hi Nat,

    I have been trying IF for a few months now and I am finding it really hard to fast past the 14 hour mark, particularly on work days. Do you have any tips on getting to 16 hours? Or is there even any more benefit by going the extra 2 hours?

    This week I am also doing your 5 day cleanse after the holidays! Which is a welcome break for my gut!! But whilst doing IF is it necessary to eat the three meals a day? I find the three meals a day a bit of a mental hurdle I am yet to jump and maybe why I can’t make it past 14 hours – the need to eat breakfast before lunch.

    Any suggestions would be great,

    Thanks for all your great advice

    Emily x

    • January 18, 2018 By Nat Kringoudis 11:23 pm

      Emily are you eating enough good fats when you eat? That may help. I also think of it sometimes is a mental game although if it is around your menstrual cycle that can play in too. Some experts say 14-16 hours. I think whatever works for you.

      • January 19, 2018 By Emily 4:41 am

        Thank you! I will try adding some more healthy fats. And yes I was wondering if it was some sort of ingrained mental conditioning “breakfast is the most important part of the day” that we are taught so young!

  • March 14, 2018 By Kiri 1:21 pm

    Hi Nat, this may sound like a silly question. But define fast? I understand we can drink water? What about lemon water or herbal tea?

    • March 22, 2018 By Nat Kringoudis 2:58 pm

      Yes you can certainly have water and herbal tea. x

  • November 12, 2019 By Ranelle 8:48 am

    Are you able to drink an almond milk coffee with maca and medicinal mushrooms during intermittent fasting?

    • February 21, 2020 By Nat Kringoudis 10:33 am

      That would be considered breaking the fast.

  • January 15, 2020 By Nelly 8:44 am

    Hi Nat,
    Are you able to drink almond milk coffee while fasting? Thanks 🙂

    • February 21, 2020 By Nat Kringoudis 10:31 am

      That would be considered breaking the fast. Black coffee, black tea, herbal tea or water is what you can have that won’t do that.

  • February 20, 2020 By Tina 1:20 pm

    Is it just as beneficial for men to fast the way women should?

    • February 21, 2020 By Nat Kringoudis 10:29 am

      Yes indeed! Beneficial for both.

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