Does intermittent fasting (IF) affect fertility in women?

Intermittent fasting and time-restricted eating have gained popularity as a method of weight loss. But is it as good as for other health parameters? A recent study, published in The Royal Society, showed how model organisms —zebrafish — had a poor quality of sperms and eggs in response to the long break in the eating cycle because of fasting. Though the study was restricted to fish, it is believed that the same dietary habit may have a similar impact on humans. Dr. Shruti N Mane, consultant fertility expert at Motherhood Fertility and IVF, Navi Mumbai, cautions about its impact on your hormones.

1. Many use fasting as a way to lose weight. How is intermittent fasting different from other types of fasting?

Intermittent fasting is an umbrella term used for alternate day fasting (ADF), the 5:2 diet and time restricted eating (TRE). One adopts various ways and means to battle the bulge. Alternate day fasting (ADF) involves a feast day where individuals eat ad libitum (meaning that you can eat as much food as you want), alternated with a fast day where individuals can consume only water. The 5:2 diet is a modified way of ADF where individuals have five feast days and fast for two days per week. TRE involves an eating window for a limited number of hours in a day and fasting with zero calorie beverages for remaining hours of the day.

But one should speak to an expert and weigh the pros and cons before following any diet. Moreover, choosing any diet without the expert’s knowledge is a strict no-no. It can lead to severe complications and impact one’s overall well-being.

2. Can this kind of diet have negative effects on eggs and sperm quality?

In women, intermittent fasting can negatively affect estrogen levels and other reproductive hormones, leading to menstrual irregularities and fertility issues. According to studies, the way organisms respond to food shortages can lead to a negative outcome when it comes to the quality of eggs and sperm.

Also, the female pituitary gland is sensitive to caloric intake. Below a certain level, signalling proteins like kisspeptin could decrease, thereby causing levels of LH and FSH to drop. Unfortunately, the only studies confirming this have been done on animals.

For a regular menstrual cycle and regular ovulation, women need enough energy (calories) and adequate body fat. If you restrict food intake too much, your body thinks you are in “danger” and conserves energy by reducing estrogen and progesterone as your hormonal axis, (hypothalamic-pituitary-ovarian axis) goes into sleep mode.

This means your ovulation process is hindered and will not occur, hence causing irregular or no periods also known as hypothalamic amenorrhoea.

A drop in Dehydroepiandrosterone (DHEA)—a hormone that helps to produce hormones, including testosterone and estrogen— has been observed after a TRE diet for a period of eight weeks.

In females, a drop in DHEA levels are shown to negatively affect egg quality, causing reduced libido, vaginal dryness and osteoporosis. Studies have also shown that supplementing DHEA may improve success rates in females undergoing fertility treatment.

Fasting can impact puberty and growth of pre-pubertal girls. It has been found that time-restricted intermittent fasting reduces blood sugar levels and increases insulin sensitivity which can be a benefit to a certain group of patients diagnosed with PCOS.

3. What do the other global studies indicate?

In a study—‘Effect of intermittent fasting on reproductive hormone levels in females and males’—it is stated that intermittent fasting decreases androgen markers (i.e testosterone and free androgen index) while increasing the serum hormone binding globulin levels in women with premenopausal obesity.

These androgen markers are important during follicular development and for estrogen synthesis. A decrease in their level may in return negatively impact the estrogen levels in the female body, hence hindering the process of ovulation.

Studies conducted on female rats in 2013 by S Kumar have shown that intermittent fasting leads to a suppression of reproductive hormones and even slightly reduced size of their ovaries. Dr Varady and her team discovered that after eight weeks of dieting, DHEA significantly declined by about 14 per cent.

Studies on athletes, who often follow strict diets, have shown that their monthly cycle can be affected when the body spends too long in “negative energy balance” (more calories are being burned than being eaten). This can occur even if the body is deprived of energy just for a part of the day as might happen during intermittent fasting.

4. Have you come across patients whose fertility got impacted due to intermittent fasting? Does it affect the nutritional intake?

One of my patients did bear the brunt of following the fad of intermittent fasting. She started with TRE only for the purpose of weight loss and continued it for a period of three months. She did manage to lose 7 kg over a period of three months with TRE. However, it was not possible for her to continue with the trend due to the associated side effects with intermittent fasting such as headaches, feeling fatigued all the time, hunger bouts at odd times and constipation. She presented to me with complaints of irregular periods and intermittent spotting.

This shows that putting your body through extremes causes a shift in your hormones, thereby affecting ovulation and your fertility. If not done properly, intermittent fasting can lead to malnutrition.

If a person engages in very long fasting periods and doesn’t replenish their body with enough nutrients, this could result in malnutrition and associated health complications. The same goes for poorly planned continuous energy restriction.

That’s why it’s essential to consume a well-rounded, nutritious diet while practising intermittent fasting. Make sure you never overly restrict your calorie intake. A healthcare professional who’s experienced in intermittent fasting can help you come up with a safe plan that provides an appropriate number of calories and the right amounts of nutrients for you.

5. What precautionary measures need to be taken for a fasting diet?

There is also absolutely no evidence that intermittent fasting is helpful for fertility. And if you become pregnant, intermittent fasting is definitely NOT recommended during a time where so many nutrients are required to support new life.

It is better to get yourself evaluated before following any type of diet. Do not follow any diet just because your friend or family member is doing it or your favourite celebrity is doing it. Apart from that, many people also take the help of these kinds of diets after they go viral on social media. This is not at all advised. These diets can do more harm than good. They are not suitable for all body types. They can cause irreversible severe complications that can steal your peace of mind.

It is better to stay in touch with a fertility consultant, who will guide you regarding reproductive health. You will be advised on nutrition and exercise after assessing your overall well-being. If you have any doubts. then you need to get them addressed by a fertility consultant. Apart from diet, one will also have to pay equal attention to other factors like exercise, stress, sleep, pollution, and certain conditions in men and women that impact fertility.