Intermittent Fasting

Intermittent Fasting – Is it different for Men & Women?

Unless you are new to LCHF you’ve probably been hiding in a cave if you haven’t heard of intermittent fasting (IF).  IF is a term used for a set period of time during which you do not eat. It is a bit different to conventional fasting where you can go for days without eating usually for a spiritual reason. With IF you will typically choose a ‘window’ of time each day or once a week where for from 8-16 hours you won’t eat any food. There are also dozens of versions of IF just to complicate things. These vary from around 6-72 hours. You’ll need to choose how long you personally wish to go without food. Remembering that the object here is to cut down on the amount of food you are eating and still carry on living normally without affecting your metabolic rate.

Let’s just get one thing straight at the outset – IF works well for men, and 99% of the time it works really well for them.  When it comes to women the results vary significantly.  Men and women respond very differently to lifestyle modification and diet, and because life’s not fair, men seem to do far better on all these lifestyle modifications than women, so it makes sense to concentrate mainly on women in this article having just stated that IF seems to work well for men.  Most people regard IF as missing lunch or lunch and dinner for a day, while others miss lunch every day.  There is no hard and fast rule as to how long you will go without food or how many meals you will miss.

Women appear to have a different experience very often, typically suffering anxiety, insomnia, irregular or total cessation of periods and may encounter other hormonal problems when they follow IF regularly.  When a woman’s caloric intake drops below a certain level her energy declines, stress levels rise and her hormones are adversely affected.  There is a small category of men who have a similar experience but it takes much longer to manifest. Reducing fat and caloric intake also reduces fertility in women – some may even enter early-onset menopause.

In my 23 years of experience I have seen women lose weight this way. However, typically once they return to even a very low carbohydrate diet they will put on some if not all the weight lost and often with interest.  There is also the temptation to over-exercise while fasting. Again once one’s lifestyle returns to normal weight gain is likely.  Reducing food intake, meal frequency, caloric restriction and excess exercise can lead to adrenal fatigue in both men and women. Women will however react much sooner and more severely than men.  Adrenal fatigue has a whole new set of problems thus making weight loss more difficult and requiring a strict protocol to overcome.

Clearly there are times to fast but these instances are generally when we have a tummy bug, are distressed, or have a spiritual reason to do so.  Fasting is definitely also something which can be beneficial when done correctly, however too-regular IF can slow metabolism causing thyroid and general endocrine mayhem in many women.  If women do fast, shorter periods of time would be more beneficial than longer ones.  Never fast with adrenal issues, pregnancy, if you are on chronic medication or unsure of how to embark on an IF – check with a qualified LCHF health practitioner first.

Another thing to consider with frequent IF is that the less you eat, the less nourishment you are getting into your body, whether male or female.  So when you do eat, it needs to be nutrient-dense food – not a cup of coffee.  Animal protein with fat, and nutrient-dense vegetables are very important – if you embark on IF then when you do eat, make the meals count.

Hormones, especially women’s, are very sensitive to energy intake.  Let’s look at the hypothalamic-pituitary-gonadal (HPG) axis (three endocrine glands which work together).  First the hypothalamus will release gonadotropin releasing hormone (GnRH), which tells the pituitary gland to release luteinising hormone (LH) and follicle stimulating hormone (FSH).  The LH and FSH then act on the gonads (ovaries or testes).  In women, estrogen and progesterone are triggered for ovulation and pregnancy, and in men the production of testosterone and sperm.  In women, this sequence of events must happen with great precision during her cycle; GnRH needs to be precisely timed or her hormones will become disrupted.

Nobody is altogether certain as to why women are so sensitive to IF, but it is suspected that a protein-like molecule called kisspeptin, used by neurons to communicate with one another, may be responsible as it stimulates GnRH production in both men and women and is very sensitive to leptin, ghrelin and insulin.  Women produce more of this molecule than men so their sensitivity to change may be heightened.  There are no studies done on humans at this point, but rat studies showed IF negatively influenced reproduction in young rats.

The key here is to recognise that the female reproductive system and metabolism are deeply intertwined.  Missing periods means your hormones are disturbed, not only your sex hormones, but all your hormones, including those that store fat and those that help you burn fat.  Eating too seldom as in frequently repeated IF, means less protein intake and protein deficiency impacts negatively on fertility.  Too little food can also be seen as an independent stressor on the body.  Stress leads to raised cortisol levels which then inhibit GnRH, suppressing the production of estrogen and progesterone by the ovaries.  In fact during periods of stress, progesterone is converted to cortisol to help the body cope, and this can prevent weight loss (or cause weight gain).  Anything which affects reproductive health will affect overall health, weight management, fitness and wellbeing. If you are finding IF stressful it probably isn’t for you.

There are less extreme versions of IF though where you simply miss a meal.  Try it out and see how you respond.  If you experience any of the following it should be discontinued: hair loss, insomnia, menstrual irregularities, acne/rashes, slow recovery after injury, decreased tolerance to stress, mood swings, palpitations, reduced libido, slowed digestion and constantly feeling cold.

IF is not a magic bullet – it is a tool to be used wisely and is contraindicated if you are:

  • Pregnant
  • Stressed out
  • Suffering from an eating disorder
  • Battling to sleep
  • On chronic medication
  • Are suffering from any sort of chronic illness (unless medically supervised)

IF usually last from 12-72 hours. However a 16 hour fast (during the night) is the most common.  While there are some very powerful and positive effects particularly in diabetics there are also some negative ones.


  • May encourage weight loss
  • Reduces insulin levels in most people
  • Boosts energy
  • Enhances mental alertness
  • Promotes better immune function

Adverse effects may include:

  • Insomnia
  • Anxiety
  • Irregular periods and amenorrhea
  • Hormonal imbalances
  • Cystic acne
  • Decreased glucose tolerance and insulin sensitivity (strangely enough)
  • May shrink the size of the ovaries

Stefani Ruper – a regular blogger in the Paleo community in interpreting the scientific research on IF says of some of the studies she’s looked at. “Sex differences were relevant in two striking areas: (1) women in studies covered by the review did not experience increased insulin sensitivity with IF regimes and (2) women actually experienced a decrease in glucose tolerance”.  It seems almost all men had good results while women had metabolic dysfunction without an improvement in insulin sensitivity. Clearly more studies need to be done. Especially in the case of women but right now there’s little to go on other than anecdotal evidence from individuals.

So then, let’s say you do decide to try this, here are some helpful tips:

  • Plan ahead how and when you are going to start and when you are going to eat again
  • Make sure that you remain well hydrated with fresh, clean water
  • Stay away from caffeinated drinks and bulletproof coffee
  • You could drink a few cups of pure bone broth (recommended)
  • Try to find a way to do something relaxing (walk, pray, massage, etc)
  • Increase your salt intake
  • When you break the fast, make certain you eat nutrient-dense healthy food
  • If you do well on this fast. Plan another one but not too soon. Give it a week’s break at least.

Don’t beat yourself up if this doesn’t work for you.  Nothing replaces regular intake of really healthy clean food. It is nutritive and helps to keep the body’s organs detoxified and functioning correctly. At the end of the day we need to remember health is about eating the correct foods not avoiding food.

Remember too that there are very distinct benefits to IF in those who do well on it, including increased energy, improved cognitive ability, memory, improved insulin sensitivity and when done correctly, without lowering the metabolic rate.  Improved immunity and heart health is also a bonus for some people.  In those who don’t do well on IF they will experience the polar opposite of the above. With the unwanted bonus of extra weight gain after the fast. So if it’s for you – fantastic. If not just realise that your body is not going to respond well to it and stick to a more balanced LCHF lifestyle.

The hormones in a woman’s body are programmed to prevent her foetus from starving. Even when she’s not pregnant so she will be very sensitive to anything that resembles a starvation signal.  IF is also often wrongly practised where the person goes from feasting to fasting. This will upset the delicate hormonal balance in most women’s bodies. Sometimes fasting leads to binging afterwards which is clearly an eating disorder but LCHF is about eating to hunger and not eating when not hungry. When you do eat it is with mindfulness and moderation, overdoing nothing (including fat).  Whatever happens remember you are unique with unique needs. There really is no one-size-fits-all when it comes to lifestyle and IF.  Because eating too much or too little is technically ‘stressful’ to the body sometimes you are simply better off on a 3-meal a day regimen.


Published with permission from Lose It Magazine – written by Sally-Ann Creed for the January 2017 issue.



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Originally published on on 22 January 2018.


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