Does Skipping Breakfast Impact Menstrual Health?

This episode explores how breakfast skipping, meal timing, and intermittent fasting affect hormone rhythms, ovulation, and menstrual cycle health. Learn how the body’s internal clocks respond to food timing and why aligning meals with circadian rhythms may support reproductive function.

Learn more about women's health and nutrition at whnlearninghub.com 

References:

• Cienfuegos, S., et al. (2022). Effect of intermittent fasting on reproductive hormone levels in females and males: A review of human trials. Nutrients, 14(2343). https://doi.org/10.3390/nu14112343
•  Fujiwara, T., et al. (2019). Time restriction of food intake during the circadian cycle is a possible regulator of reproductive function in postadolescent female rats. Current Developments in Nutrition, 3(nzy093). https://doi.org/10.1093/cdn/nzy093
•  Fujiwara, T., et al. (2020). Breakfast skipping in female college students is a potential and preventable predictor of gynecologic disorders at health service centers. Diagnostics, 10(476). https://doi.org/10.3390/diagnostics10070476
•  Ono, M., et al. (2025). Influence of lifestyle and the circadian clock on reproduction. Reproductive Medicine and Biology, 24, e12641. https://doi.org/10.1002/rmb2.12641
•  Schweiger, U., et al. (1992). Everyday eating behavior and menstrual function in young women. Fertility and Sterility, 57(4), 771–775.

Transcript

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Hi, and welcome to the Fem Health Nutrition Podcast. I'm Nilu De LaMi, a registered dietician and founder of the Women's Health Nutrition Learning Hub, a platform where dieticians and nutrition professionals can learn, connect, and collaborate on all things related to female health and nutrition. If you haven't already, you can check out the website at w hn learning hub.com. The link is also in the episode description. And just as a reminder, this podcast is intended as an educational podcast for dieticians, healthcare professionals, and really anyone interested in female health and nutrition. The content covered in this podcast is not intended as medical advice, and if you have any questions or concerns about your own health, please consult with your healthcare team. So I follow a lot of women's health accounts on social media, and I'm not sure if it's the algorithm or if this is a trending topic on social media these days, but i'm seeing a lot of posts about the impact of skipping breakfast on hormone health, and that kind of inspired me to. Focus today's topic on whether skipping breakfast can actually impact menstrual health and hormonal health. It's a super interesting topic, and as always, what we'll do is first we'll talk about the theory and the potential mechanisms. We'll discuss the actual research, and we'll also look into the gaps in the literature. Now there are two major biological mechanisms that could explain why skipping breakfast and engaging in prolonged fasting could possibly have a negative impact on menstrual health. The first is circadian rhythm disruption, and the second is energy restriction and its downstream effects on hormone signaling. So we'll talk about both of these possible mechanisms. Now before we talk about these theories, I know I repeat this a lot in my content, but I did wanna do a quick review of the HBG access because I think it will give a little bit of more context to the mechanisms. So the primary hormonal access that's involved in reproduction is the hypothalamic pituitary gonadal or the HP Gxi. So the hypothalamus, which is a structure in the brain, will secrete a hormone called gonadotropin releasing hormone or GnRH, which stimulates the pituitary gland. Also, a structure in the brain. To release two hormones, izing hormone, also referred to as LH and follicle stimulating hormone, also referred to as FSH. These hormones will then act on the ovaries to regulate estrogen, progesterone, and ovulation. Okay, so first we'll talk about the circadian rhythm and how this is connected to breakfast and menstrual health. So the circadian system regulates many, many physiological processes over a 24 hour cycle. So this includes sleep and wake timings, metabolism, and hormone release as well. So the circadian rhythm is governed by a central clock in the brain. Called the schematic nucleus or the SCN, and there are also what we call peripheral clocks in tissues like liver, adipose tissues, ovaries, and the uterus. Now synchronization between that central clock in the brain and the peripheral clocks in the tissues is really essential for proper reproductive function, including the timing of the release of what we call GNRH pulses that trigger ovulation. Now, meal timing is actually one of the most powerful time cues for resetting the peripheral clocks in the reproductive tissues. So eating early in the day acts as a time cue for the circadian clock, which helps. Synchronize hormonal rhythms in the brain and the peripheral organs like the ovaries. So when a meal is eaten early in the morning, this actually supports the pulsitile release of GNRH from the hypothalamus, which is necessary for then stimulating LH and FSH from the pituitary gland. When breakfast is skipped or when meals are concentrated later in the day, like with some intermittent fasting patterns, for example, or for people who just are in a rush or don't have an appetite in the morning and skip breakfast, these internal clocks can become desynchronized. And when this happens, when this desynchronization happens, it's been shown to alter that pulsatile secretion of that GNRH, which then reduces the release of LH and f. From the pituitary gland, and again, these are key hormones for ovulation and menstrual cycle regulation. So in simple terms, eating earlier in the day helps keep the body's internal clocks in sync, supporting those healthy hormone rhythms. When breakfast is skipped or meals are delayed, it may disrupt these signals potentially affecting ovulation and menstrual cycle regularity. Now another possible mechanism is the impact of energy restriction on hormone signaling. The female reproductive system is highly sensitive to energy availability, so even in an individual with normal body weight, normal body fat percentage. When there's a perceived energy deficiency, whether it's from undereating or high levels of physical activity, or even something like irregular meal patterns, this can trigger an adaptive suppression of the hypothalamic pituitary gonadal or HPG axis. And this is why sometimes in female athletes, for example, we might see that they may develop hypothalamic a amenorrhea, which is a condition where menstrual periods stop for a period of time due to those disruptions in the signals from the hypothalamus. Now one of the key hormonal signals involved is leptin. And leptin is a hormone that is secreted by adipose or fat tissue, and it plays a role in communicating energy sufficiency to the brain. And when leptin levels are adequate, they can stimulate the hypothalamus to release gonadotropin releasing hormone, which then initiates. The hormonal cascade that's needed for ovulation. When meal frequency is reduced or fasting periods are extended, so for example, with skipping breakfast or intermittent fasting, or just skipping meals in general, leptin levels may fall, even in the absence of weight loss. These low leptin levels may then signal an energy deficit, and the hypothalamus then responds by reducing gonadotropin, releasing a hormone ity. Leading to decreased LH and FSH secretion, and as we discussed earlier, the downstream effect of that is delayed or absent ovulation or other impacts on menstrual health and menstrual cycles another hormone that could impact this process is cortisol. And prolonged fasting and perceived energy scarcity could be a stressor that could potentially increase cortisol and when cortisol levels are high. This may also inhibit that gonadotropin releasing hormone secretion impact menstrual health So together, when we look at these mechanisms related to the circadian rhythm and energy suppression, these could offer a possible explanation for why irregular mealtimes and skipping breakfast may impair men function. So now that we've discussed the theory, let's look into the actual research. And as with many topics in women's health, this is actually an area where there hasn't been as much high quality research done. So we definitely need more research in this area, but I'll review some of the studies that I found. So there was an interesting animal study that was done to explore the effects of meal timing on reproductive health. Now, in this study, they had female rats who were post adolescents, and these rats were divided into three groups. So we had the control group where these rats had free access to food. Then they had night fed rats and night fed rats are basically rats that have food access during their active phase because rats are nocturnal. So the night for them is the active phase, just like the day for humans is the active phase. They also had a group of day fed rats. So these are rats that had access to food only during their inactive phase And what they found was that despite equal total calorie intake, the day fed rats whose feeding was misaligned with their natural circadian rhythm had suppressed ovulation and impaired follicular development. So this study suggested that in these female rags, meal timing rather than energy intake, can act as a determinant of reproductive function. The mechanism that's driving this probably involves that desynchronization of the central and peripheral clocks that we talked about earlier Now, of course, we can't take this study on rats and directly apply to humans. But it does suggest that more research is warranted in this area. So when it comes to human studies, there was one large cross-sectional study of over 3000 female university students, and this study was conducted in Japan and in this study they found associations between breakfast skipping and menstrual disturbances. So they found that participants who regularly skipped breakfast had higher rates of painful periods, or dysmenorrhea irregular menstrual cycles. And greater psychological burden associated with menstruation. And the authors of this study proposed that this association, they found may be due to that disruption of the circadian rhythms that normally regulate that HPG axis. Now of course, we do need to note here that this was a cross-sectional study, so although it can give us information about an association, we can't really confirm that skipping breakfast is what caused these symptoms. And we really do need more randomized control trials. Another study that's cited a lot in the literature and this. Tells you how little research there has been done in this area is a study from 1992 and in the study they prospectively looked at 22 healthy women aged between 18 to 24. And the participants were assessed for their dieting behaviors, and they were grouped into either high or low dietary restraint categories based on eating behavior questionnaires, and what the authors found is that those who had what they called a higher cognitive dietary restraint, so those who were basically dieting and restricting energy, more experienced significantly lower mid luteal progesterone levels. As a reminder, that luteal phase is that second phase of the menstrual cycle. And in the lute phase, progesterone levels will increase typically, and those increased progesterone levels play a role in thickening the uterine lining to prepare for the potential implantation of an embryo and pregnancy. They also found more frequent short lute phases of less than nine days, and shortened lute phases can also impact fertility. And they also found that they had a higher incidence of cycles where they did not ovulate. And the authors comment in the study that these findings occurred in women even when they were not underweight or malnourished. Suggesting that these behavioral patterns around food, like skipping meals or restricting intake can independently suppress reproductive hormone function. So when we look at these studies together, they do show that even in the absence of low body weight or low body fat, inconsistent or delayed eating, especially skipping breakfast, could possibly impair ovulatory function. And this could be both through metabolic and circadian pathways. Again, we do need more randomized control trials, larger studies to confirm these findings. Now, I did also want to talk about polycystic ovarian syndrome in this context because there are some studies that show that intermittent fasting could potentially help with PCOS So we have a conflict there. We have some studies that are showing that intermittent fasting could potentially help with insulin sensitivity and HYPERANDROGENISM and PCOS. And then we have these possible mechanisms and these other studies that are showing that skipping breakfast can have negative consequences. But when we zoom in a little bit, it seems that yes, possibly time restricted eating or intermittent fasting could be beneficial for some people with PCOS, but it seems like the timing does still matter. So there was a review done in 2022 by a group of researchers, and they analyzed several human trials that use different versions of intermittent fasting with a particular focus on time restricted eating, Which is a dietary approach where eating is confined to a certain window of time each day, and they compared the outcomes of two different types of time restricted eating. So they looked at early time restricted eating. So this is one, the eating window was earlier. So for example, from 8:00 AM to 4:00 PM. They also looked at late time restricted eating, which is when the eating window is later in the day, like 12:00 PM to 8:00 PM which is that time window that a lot of people actually follow when they're doing intermittent fasting. And now when they looked at the effects of early time restricted eating, they found that it was associated with improved reproductive hormone profiles, and it showed reductions in total testosterone and free androgen index and increased sex hormone binding globulin or SHBG levels and combine these changes may help reduce hyperandrogenism, which is a key feature of PCOS that does contribute to that ovulatory dysfunction. So basically, when that time restricted eating aligns with the body circadian rhythm. It may produce those favorable hormonal effects. Now, when they looked at the effects of later time restricted eating, so that 12 to eight window, it did not consistently produce the same improvements in hormone levels, and sometimes the effects were either less pronounced or negligible. And the author suggested this is possibly due to a circadian misalignment. Now I do want to mention here that it is very possible to improve PCOS symptoms with the various other strategies that do not involve any time restricted eating, and I'll save that for another episode. I personally don't recommend. Intermittent fasting or time restricted eating to my PCOS clients as a first line strategy, and that's really to respect and maintain their relationship with food. But there are some people who are curious and they've read some studies and have read some research, and they want to try it. So for those people who are really keen on trying some fasting regimens, We do try to move it to an earlier time window for them. Now, as you can see from some of the research I have presented, one was an animal study, the other wasn't from 1992. The research in this area is really lacking, so we don't have enough randomized control trials. Most of the evidence currently comes from cross-sectional or observational studies, or short-term animal trials. There is a bit of a lack of diversity in the participant study, so most human studies are actually conducted in young, healthy, cisgender women, a lot of whom are in school or in university. So we can't apply these findings to everybody who menstruates. And as I mentioned, some of these studies are quite outdated, and while they still might have some relevance, we do need updated methodologies and larger sample sizes to confirm these findings. So as a dietician or nutritionist or healthcare professional, what can you do? The first thing you can do is to encourage your clients to eat breakfast within one to two hours of waking. And this is especially important for those who are experiencing any sort of menstrual irregularity or fertility challenges. It is true that the research is still developing and we need more studies to confirm the effects of skipping breakfast on hormone rhythms. As more research comes in, I think it is a good idea to err on the side of caution here and to promote having breakfast and those who are experiencing menstrual or fertility challenges. We also want to be cautious with intermittent fasting and clients who have a history of irregular cycles or hypothalamic a amenorrhea as these individuals may be more sensitive to energy restriction. And for those clients with PCOS who really want to try time restricted eating, then we would suggest an earlier eating window and to monitor the patient very closely. Thank you so much for tuning into this episode. As always, you can find the references in the description of this episode. If you enjoy today's episode, don't forget to rate, follow, and share the podcast. Subscribing really does help others find this content and will also keep you in the loop for future episodes. Thank you so much and I hope you have a lovely day.