Intermittent Fasting – Why Some Women Have to be Careful with It

What are the reasons intermittent fasting is not reflected positively in some women

Intermittent fasting (or also known as cyclic feeding) is a diet with lots of options for the application that promises a number of health benefits.

Some of the positive effects as a consequence of such a system are:

  1. Improving insulin sensitivity;
  2. A protective role on the central and peripheral nervous system;
  3. A protective role on the cardiovascular system;
  4. Creates preconditions for larger weekly / monthly calorie deficit compared with other modes (and this is a plus for the reduction of weight);
  5. Helps accumulation or maintenance of body massIntermittent Fasting

Years ago, when people began to speak more about intermittent fasting, there was a boom in periodically starving people. It became a sort of “new trend” that everyone should try, without thinking whether it is optimal for his/her body.

I was no exception – I love to experiment, and I had quite unnecessary fat and intermittent fasting promised namely success in downloading them. At the beginning I felt great – positive changes were visible very soon. But only to a point, after which it took a twist and instead feeling good, the opposite happened. Later I realized that I was not the only one who had bad negative effects. Intermittent fasting turned to be another proof that there is no universal truth, mode and program.

In the early 2015 precision nutrition focused on periodic fasting and women and why this diet is even a risk for some of them.

We decided to look at some research and what affect female hormones to show the other side of the coin. So every woman will be able to determine what would be appropriate for her.Intermittent Fasting

Female hormones and their sensitivity

In the body, everything is connected, and endocrine glands serve important and overlapping functions. The hypothalamus is the part of the brain that plays a key role in the balance of hormones in the body. It produces a group releasing hormones that in turn activate the secretion of pituitary hormones. When the hypothalamus releases gonadotropin releasing hormone (GnRH), pituitary responds with release of luteinizing hormone (LH) and follicle stimulating hormone (FSH).

In women, these two hormones control the release of estrogen and progesterone from the ovaries (respectively help allow ovulation and reproduction).Often infertility may be due to hormonal disorders and subsequent menstrual disorders and loss of ovulation. This problem can be started at all levels of relations between the hypothalamus, pituitary and ovaries. Part of the disturbances which may affect, caused by changes in the environment, emotional and physical stress, excessive weight loss (here comes the extremely low percentage of fat).

The release of GnRH is affected not only by far these reasons, but also by starvation, which can reduce the secretion of the hormone, and thus to follow disorders and in other systems.

Every body reacts differently to external stimulus – when many women do not observe negative effects while others do not feel good with periodic fasting. Women are generally more sensitive to this type of feeding (and its variations) compared to men.Intermittent Fasting

One hypothesis for this is that women have more kispeptin, which means greater sensitivity to changes in energy balance. The kispeptin is a protein which in humans is encoded by the gene KISS1. It stimulates the secretion of gonadotropins, it can stimulate the release of aldosterone and insulin induces the production of LH and FSH, which are required for the onset of puberty and menstruation in women.

What is the relationship of all these information with intermittent fasting?

To examine the relationship between energy statuses, the release of hormones, links between the different systems and how they affect the female body we will look at one research (1). It is important to clarify that at this stage a similar experiment is not made with people and for this purpose are used rats.


The study included male and female rats, aged 3-4 months and weighing 150-200g. The animals are not sick and are housed in 3 cells with 12 hours of light and 12 hours dark conditions. They were divided into two groups:

  1. Those who eat when they want (ad libitum – AL);
  2. Those who are subjected to periodic fasting and food is controlled by the people, placing and removing it a further specified intervals (intermittent fasting dietary restriction – IF-DR).

The experiment lasts 12 weeks (3 months) with a controlled collection of data (every 15th day were recorded body weights and levels of glucose in the blood of all the rats and compared between the two groups).Intermittent Fasting

Female rats of the second group were subjected to 8 week feeding then (refeeding – DR-R).

The water of all rats was unlimited.


Body weight, glucose levels in the blood, sexual desire, histology of the ovaries

After completion of the experiment, 12 weeks, it was found that the level of blood sugar in intermittent fasted rats of both sexes, is considerably lower compared to the animals that are fed ad libitum.

Female rats of intermittent fasting reduced the weight by 19%.

In female rats IF-DR group show reduced weight ovarian large size of the corpus luteum and fibrous tissue compared with AL and DR-R (supplied after periodic fasting) groups.

LH, estradiol and testosterone

Serum levels of LH in both sexes periodically fasted rats were lower than those of the group Eating desired.

Estradiol of females and testosterone of male rats of IF-DR group were significantly lower compared with the respective gender group of AL.

Serum leptin levels – Serum leptin in female animals of the IF-DR were significantly lower compared to women AL. Moderate decrease was also observed in males.

Kispeptin – There has been a reduction in the effects of kispeptin female rats from intermittent fasting group.

Gonadotropin-releasing hormone – There is a decrease in the secretion of GnRH in animals that underwent intermittent fasting compared to others who ate at will.

It is difficult to find evidence that this same pattern can be observed in humans, but is supposed to starvation in some women may reflect a similar way.

Low kispeptin and estrogens in women

When kispeptin levels fall, this can cause irregular menstrual cycle (your cycle comes in a larger intervals than usual, it misses several months, etc.). Maybe some women who find themselves in such a situation will not think about the consequences of systematically missing cycle if it coincides with the period in which they do not want to become pregnant.

Female reproductive system and metabolism are linked and the absence of several monthly cycle means that somewhere there is serious confusion of hormones and not just those that are relevant to getting pregnant.

One possible story why most women do not respond well to intermittent fasting is that they consume less protein than men in general, and among intermittent fasting women found those who consume even less than required for normal functioning of the body.

This means that the amino acids necessary for the activation of the estrogen receptor and the synthesis of insulin-like growth factor in the liver, are also in insufficient quantities.

Insulin factor helps the thickening of the lining of the uterus to continue the reproductive cycle.

Therefore, low protein diets can reduce fertility.

Estrogen is involved not only in reproduction but also in many other processes. If this hormone is not in the normal range, it can change metabolic function, mood, digestion, recovery, bone formation, etc.

Estrogens modify peptides that signal that we are not hungry (cholecystokinin) and hungry (ghrelin).

If estrogen levels fall considerably, it can lead to a sense of greater hunger and desire to eat more than you would under normal circumstances.

Why intermittent fasting may adversely affect some women?

Through various studies it is clear that a woman’s hormonal balance is sensitive to the type, quantity and frequency of meals. The reproductive system is affected not only by the percentage of body fat, but the total caloric balance.

There are women who tend to maintain a very strict calorie deficit, while intermittent fasting this opportunity is even greater.

Since there are different options for intermittent fasting (some are more extreme than others), the body may not respond well to your chosen diet, if you treat it as a stress factor (if it is available too little food shortage of some nutrients combined with excessive exercise and / or stress, insufficient rest / recovery).

How do I know if intermittent fasting is for me?

Perhaps if you are a woman and you start thinking about intermittent fasting, you are currently wondering how to tell if it is for you and how it will affect you.

There is no way to know unless you try, but start with softer protocol compliance and watch carefully. This means even choose an option in which the phase of starvation is possibly short.

Be sure that caloric restriction is not too big and not putting your body in a stressful situation.

Optimize and quantity of individual macronutrients so as to give everything to your body for the flow of vital processes.

End intermittent fasting if:

  1. Your menstrual cycle stops or becomes irregular;
  2. You have trouble sleeping (difficulty falling asleep or continuously you are sleeping);
  3. Your hair starts to fall and / or the health of your skin break;
  4. You are not recovering well after workouts;
  5. There are sudden changes in your mood;
  6. You disturb digestion;
  7. You constantly feel that you are cold.

Do not start intermittent fasting if:

  1. You are pregnant;
  2. You are unstable psyche and have problems with self-perception;
  3. You tend to lurch into extremes;
  4. You have ulcers / gastritis;
  5. You have diabetes and are taking insulin (if you have diabetes and are being treated with tablets, it is necessary to discuss the possibility of intermittent fasting with your endocrinologist);
  6. You are chronically exposed to stress;
  7. You do not sleep well;
  8. You are not well aware of the key points in nutrition and exercise.

The ways to achieve your goals are many and there is no universal diet. If you have tried the lightest version of intermittent fasting and it is not good for you, it makes no sense to continue with more extreme options.

It is important to monitor yourself and if you notice any side interference, to consider changes. Do not continue with intermittent fasting, ignoring the symptoms.

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