You are aware of the potential pitfalls of excessive fasting and keto on your hormones (if you haven’t read Part 1- WHY EXCESSIVE KETO AND FASTING MAY BE THROWING OFF YOUR CYCLE, WEIGHT LOSS AND SHINY HAIR , check that out first so you know what I am talking about in this article). But you have also have read about the great health and anti-ageing benefits of keto and fasting, and don’t want to miss out on these. So now what? This article will talk you through how and when to implement keto and fasting into your monthly cycle strategically, so you can reap what they have to offer, while keeping your hormones balanced and happy, your fertility ramped up, periods pain-free, and yourself lean, calm and radiant.

(Note: This article is tailored to the woman in her reproductive years. I will write a separate one for postmenopausal tweaks).

As described in detail in the previous article, women’s hormones in their reproductive years follow a distinct monthly cycle.

In the first half of the monthly cycle (with day 1 being the first day of your period), we have generally low hormone levels. Around day 12, we should have a rise in estrogen, which in turn then triggers a ‘LH’ surge which initiates ovulation on day 14. We need a strong LH surge and ovulation to be ‘fertile’, but also in order to subsequently build a good ‘corpus luteum’ which will release adequate amounts of progesterone throughout the second phase of the cycle to mature the uterine lining, support a potential nesting of an egg, and reduce PMS symptoms like painful breasts, mood disturbances or spotting.

A commonly observed problem with excessive fasting and too low calorie intake is anovulation (no ovulation occurs), with subsequently too little progesterone produced. Estrogen levels may be normal, but as the ratio is the most important thing that matters, you still display symptoms of estrogen dominance, notably spotting, PMS and/or infertility.

The other common picture seen with excessively being in a ketogenic state is too much estrogen overall (I went into detail on why that is, CPY17a1 enzyme upregulation and more in the previous article), which can lead to problems like endometriosis and other unwanted growths.

How to incorporate keto and fasting into your monthly cycle

As you can see in the graphs pictured above, the initial phase of our cycles are quite low in hormones. This is the time that is safest to experiment with and include fasting strategies, as not as much can become derailed. If you would like to go keto, and maybe include some more advanced fasting techniques like OMAD (one meal a day) or the Fasting Mimicking Diet, choose day 1 to 10/11, and just after your ovulation, days 15-17 of your cycle. This is also the time where your body generally responds better to higher intensity exercise, partly due to its lower body temperature and higher stress resilience. A range of 25-50g of carbs is usually cited to get into a ketogenic state. I generally see better results longer term if women stick to the higher end of this range (45-50g of carbs, which equates to roughly one portion of a starchy carb like a banana or small handful of quinoa etc plus plenty of low starch vegetables), to give the thyroid something to work with long term.

Ovulation boost

During the days leading up to ovulation (day 12-14), it is crucial to signal to the body that it is ‘safe to make a baby’ – we want to ramp up kisspeptin, a signaling molecule that will communicate to the brain to release the necessary hormones for ovulation (E2 surge, LH surge). Kisspeptin has been shown to become upregulated by eating, both fats and carbs, and downregulated by shortage of foods, overexercising (the body thinks it is running away from a tiger – aka, not safe to ovulate). This is the ideal time to have a ‘cheat day or two’, indulge in a few of your favourite treats that you may generally not allow yourself, and overall increase calorie intake slightly.

Progesterone boost (days 18-28)

During days 18 to the end of your cycle (depending on the length of your cycle approx. day 28), we want to make sure we support progesterone and avoid excess estrogen production. Being in ketosis during extended periods of your day is now not advisable, as it would upregulate CYP17a1 too much, and result in excessive estrogen production. Excessive fasting during this time will signal ‘danger’ to your brain and drop progesterone production.

A good rule of thumb for this time therefore is to add in slightly more carbs (think 2 portions, rather than the 1 during Phase 1), getting your carb intake to more than 50g, and kicking you out of ketosis for most of the day. If you practise high intensity exercise you may even want to add an additional portion.

Make sure to get enough protein during this phase, a rule of thumb is 1.3g/kg of body weight, in addition to enough iodine, zinc, selenium, vitamin A. These are all crucial for producing and activating thyroid hormone, which plays a role in your overall hormonal balance, but especially also progesterone signaling.

But what about intermittent fasting?

You love that newly gained feeling of lightness in the morning? The automatically lowered calorie intake when skipping breakfast?

Research is not 100% conclusive on this topic, but after going through many research papers, my recommendation is as follows:

If you are currently highly strung, very stressed already first thing in the morning, you may do better with a small protein rich breakfast than fasting until noon. Your cortisol is already upregulated, and adding another ‘stressor’ (fasting and maybe even coffee) on top of that would not be advisable.

If you are in a good state, stress and anxiety not running your life, than waiting until noon to have your ‘break-fast’, and maybe having a black coffee, a tea, or a coffee with some coconut oil, butter, cream of coconut milk should be absolutely ok. If your estrogen is elevated in blood tests, you may want to reduce your overall fat intake and stick to the coconut milk or black coffee version instead. If your estrogen is normal and your progesterone is low, some added good fats do more good than harm, as they are precursors to your sex hormones. Just avoid any sugary milk alternative first thing in the morning (ie oat, rice milks, or other nut milks with added sugars), as they will spike your blood sugar and get you on a rollercoaster of cravings for the rest of the day.

Eat to support your circadian rhythm

Despite their being debate about whether it is good or not to skip breakfast, science is quite conclusive about the fact that we should not start eating much later than noon, to have a protein rich meal with that ‘break-fast’ to stabilise blood sugar and reduce later cravings, to make that first meal the largest to avoid evening bingeing when the body doesn’t need the energy and calories anymore, and that we should stop eating a few hours before bed time at the latest. In fact, one study demonstrated that waiting to eat until later than 2pm, or eating past 7pm had many detrimental effects on health, including weight gain, dysregulation of sleep, brain health, and increased overall ‘ageing’ markers (see article 1 for details).

So where does that leave you?

I recommend having a (non-dairy) milky coffee/tea in the morning (optionally with a tablespoon of collagen protein powder during the ovulation and progesterone boosting days, or if your adrenals are suffering – however, do note it will likely take you out of ketosis), the first meal sometime between 10am and 1pm. Make it a substantial meal with enough protein and vegetables, and a portion of carbs to allow for tryptophan to pass into your brain to make serotonin, the happy chemical, and later turn into melatonin for good sleep. Meal no. 2 roughly 5-7 hours after your (br/l)unch, no later than 7pm, so you can get at least 3 hours, better yet 4 hours before you go to sleep to digest, to allow for a better and more restorative sleep during the night.

Comment below if this was helpful or if you have questions! Much looking forward to hearing from you. x