Intermittent Fasting (I.F.) is an abstruse but much promoted tool in the chase for optimal body composition, longevity and health in the blogoshpere.  

My own interpretation and understanding of Intermittent fasting is to create conditions of fasting in the body, but not for extreme lengths of time.

The returns of Intermittent fasting on both myself and those I see in my female clients, has allowed me to observe the complexities and cryptic nature of this tool, specific to the female sex.  I have personally experienced metabolic distress, energetic wakefulness at the wrong times, and a negative jolt to my adrenal system.  Many other women report to me that intermittent fasting causes sleeplessness, anxiety, and irregular periods, among many other symptoms of hormone imbalance, and an unhealthy relationship with food.  But I don’t see these things being mentioned in the blogosphere, ever?  

It is well-known in both the research and in nutritional communities that caloric restriction in non-obese women is disagreeable for female reproductive health. This is not news. There is an infertility condition – called hypothalamic amenorrhea – that millions of women suffer from due to being overly restrictive. But what of  intermittent fasting?

Sex differences have been revealed.  Women are more sensitive to I.F. in many striking areas:

• In a review it was found that women did not experience increased insulin sensitivity with IF regimes.

• I.F. women actually experienced a decrease in glucose tolerance. 

• In many rodent studies the female rats, stop ovulating and menstruating. They become hyper-alert, had better memories, and were more energetic during the periods in which they are supposed to be sleep.  Theoretically, according to these researchers, this is an adaptive response to starvation.  The more the female rats need calories– or at least the more their bodies detect a “starvation” state– the more they develop traits that will help them find food.  They get smart, they get energetic, they get active, and they stop sleeping.

• I.F. diets caused a relative increase in adrenal size, the magnitude of which was greater in females, compared with males.

• In females rodents corticosterone levels were significantly elevated (not so in male tests).  This suggesting a relative hyper-activation in females of the adrenal stress response to reduced energy availability.  

• I.F. caused a decrease in the size of the ovaries

• For lipids, all the rats did well: Collectively, these data suggest that atherogenic profiles of both male and female rodents are improved by dietary energy restriction.  

• In a few of the abstracts of human studies (of which there aren’t that many done on just females), human females performed cognitively much “better” (memory and alertness) on I.F. diets than on normal feeding schedules.

This last note, makes perfect sense to me, but it appears to be at a cost.  And my role is to alert you to these potential costs should you choose to delve deep into the I.F. pool.  Heightened cognition and motor activity, combined with reproductive shutdown, in females may maximise the probability of their survival during periods of energy scarcity (is this going to be beneficial to your adrenals in the long term?).  It does concern me (having been there) that it may be a catalyst for the vulnerability of women to anorexia nervosa.  I will take a deeper dive into my view on healthy relationships with food and energy intake, in a paragraph further down this page. 

Back to the note findings on studies that I viewed - There are of course some caveats to them, including that most were done on rats.  There will be exceptions to these findings and if that is you and you are seeing all positive results - all power to you.  Keep going!  This is our role as humans, to trial and test on our individual selves and hold onto what is working and let go of what is not.  

Another important distinction to make is between different body weights. Overweight and obese patients appear to experience significant improvements with IF regimes, but normal weight patients do not show the same across-the-board benefits. For women this may be a particularly sensitive issue. Overweight women may experience metabolic benefits, whereas normal weight women do not. I suspect that that may roughly be the case, but who knows. Honestly, no one at this point.

The practical solution, then, I believe, is to look at options, to be honest about priorities, and to listen to one’s body with awareness and love.

There’s some evidence that fasting can cause a “high” in females which manifest in a perpetual desire for this high that is achieved from restricting caloric intake. I have struggled with very restrictive eating in the past, and it can be super addictive…especially when you are not thinking straight (on the high)..  I love that feeling of calm, heightened awareness and response, that fasting can bring. Perhaps this illustrates the slippery slope of anorexia?  I have clients whom tell me about their experiences of fasting mornings with only coffee, which works beautifully until it doesn’t work  anymore, as their cortisol tests reveal.  There are many of my female clients whom don’t find intermittent fasting addicting (like I did, per se) but the effects for them have been interesting and helpful enough to encourage them to continue.  But alas, they have found that all good things must come to an end - even if abruptly.  

Similarly to myself, approximately 50% of my female clients have had a lot of trouble sleeping with I.F.  Some have dropped below a healthy BMI, and haven’t had a period for 2 years, tried everything to get it back,  put on a lot of weight (more than they lost) and still no sign of a period. 

The conundrum - If a woman is overweight and trying to improve her metabolic markers, and so far hasn’t had much success, should she experiment with I.F. ?  Perhaps.  Should it be undertaken if a woman is of normal weight?   What if she is a light sleeper?  What if her periods begin to stop?  What if she starts getting acne, getting a stronger appetite, or losing her appetite altogether?  These things can happen, and I do see them in women experimenting with I.F.

Granted that all women are different.  But evidence and introspection is so sparse in this area that we cannot make any one-size-fits-all statements or predictions about the effects of fasting.  In my own experimentation and that with female clients, I do recommend to everyone that a fast of twelve hours every twenty four hours should be only beneficial and has no researched evidence of any of the detrimental side effects mentioned above.  I talk about this on my Online Hormonal Balance Course for Women.  Going beyond the twelve hour period is a very individual code and needs to be approached exactly that way with Full Hormonal panel and Four Point Cortisol Testing to monitor the effects along the way.  If you can manage it - the early dinner appears to work well with women, alongside cortisol monitoring.

When making decisions of nutritional capacity I preach and value honesty with ourselves about our priorities, and acting constantly with both our mental and physical health championing in our minds.

Have your tried I.F. ? Please share your experience so that others may benefit.