Food intake is affected by a variety of neurochemical, hormonal, physiological, and psychological factors [1]. Several studies have shown significant changes in appetite, eating behavior, and energy intake in women during their menstrual cycle where there are changes to the factors affecting food intake [1].

The menstrual cycle consists of four phases, menstruation, follicular phase, ovulation, and the luteal phase. Menstruation is the first stage of the cycle, where the uterus sheds its lining. The follicular phase overlaps with this phase, beginning when the hypothalamus sends the pituitary gland a signal to release the follicle-stimulating hormone (FSH). FSH stimulates the ovaries to produce follicles, which contain immature eggs. Then, a matured follicle will cause a surge in the hormone estrogen to thicken the lining of the uterus [2].

The rising estrogen levels during the follicular phase triggers the pituitary gland to release the luteinizing hormone (LH). The release of LH begins the ovulation phase, which is the process where the ovary releases a mature egg. After the follicle releases the egg, the follicle changes into the corpus luteum. This new structure mainly releases the hormone progesterone and some estrogen to keep the uterine lining thick, which supports the implantation of the fertilized egg. However, when the egg is not fertilized, the corpus luteum will shrink and be resorbed. This resorption decreases the levels of progesterone and estrogen, causing the onset of the menstrual phase, starting the cycle again.

The variation in eating habits can be partially explained by the changes in estrogen and progesterone levels over the 28-30 day cycle. Estrogen and progesterone can impact gastric emptying (a process where the contents from the stomach are moved into the small intestine) and the secretion of some gastrointestinal hormones such as glucagon-like-peptide-1 (GLP-1) and cholecystokinin (CCK), which are important regulatory factors of appetite and energy intake [1, 3].

In fact, there is evidence from studies on rats that the hormone estrogen can increase the sensitivity to the inhibitory effects of CCK, meaning the body responds more effectively to satiation signals [4]. In a study by Brennan et al. (2009), gastric emptying, plasma GLP-1, insulin response, hunger, and energy intake were found to be reduced during the follicular phase compared to the luteal phase, as a result of a surge in estrogen and low progesterone levels.

Specifically, there seems to be a link between the rate of gastric emptying and progesterone levels [3]. Brennan et al. (2009) demonstrated in their study that gastric emptying was slower during the follicular phase, where progesterone levels are relatively low. Moreover, the study shows that GLP-1 release is higher during the luteal phase compared to the follicular phase. This is because the release of GLP-1 is related to more rapid gastric emptying as the stimulation of GLP-1 is dependent on the rate of entry of glucose into the small intestine. Thereby, during the follicular phase, where gastric emptying is slower, less GLP1 is secreted, and the insulin responses are reduced.

On the other hand, the levels of CCK were found to remain the same. However, changes in appetite suggest that during the follicular phase, women become more sensitive to the effects of CCK, and this is related to increases in estrogen levels. Hence, food and energy intakes are reduced during the follicular phase of the menstrual cycle and increase during the luteal phase [3].

Daily energy expenditure also fluctuates across the menstrual cycle. Energy expenditure is lower in the late follicular phase and higher during the luteal phase of the menstrual cycle [3]. The increase in energy expenditure is proposed to be due to the increased progesterone levels [5]. Scientists have not fully understood the mechanism behind this. Some attribute the rise in energy expenditure to the increase in body temperature during the luteal phase [5]. Progesterone has been shown to have hyperthermic effects in women. Increased core body temperature and decreased skin blood flow and skin temperature, thereby reducing energy dissipation, were consistently observed in the luteal phase, where progesterone levels are highest [6]. In line with this notion, Steward et al. (2016) have shown that treatment with depot-medroxyprogesterone acetate, a potent progestin that has twice the receptor-binding affinity of progesterone, increases resting metabolic rate and body temperature [7]. However, it remains unknown whether an increase in thermal metabolic rate is plausible to justify the magnitude of increased energy expenditure. Given the changes in energy expenditure, adjusting energy intake and appetite help ensure that the energy balance is maintained.

In a study by Kammoun et al. (2017), 30 healthy women between the ages 18-45 were assessed for food intake and body measurements, including weight and waist circumference during the follicular, peri-ovulatory, and luteal phases of the menstrual cycles. They found that the caloric intake of women, on average, had significantly increased during the peri-ovulatory and luteal phases compared with the follicular phase of their menstrual cycle, with a significant increase in carbohydrates, as well as lipids and proteins. They also found a significant increase in women’s body weight during the late luteal phase and early follicular phase, consistent with previous studies that suggest that excessive carbohydrate consumption is the cause of weight gain in the premenstrual period. However, Kammoun et al. (2017) did not report any significant changes in waist circumference in the different phases of the menstrual cycle, suggesting that variations of women’s weight during the menstrual cycle are unrelated to abdominal fat.

Moreover, the cyclic changes in energy and macronutrient intakes have been shown in several studies, with the most important changes in the late luteal phase, just before menstruation. There are often dietary compulsions during this phase of the cycle, especially for sweets and chocolate. This could be explained by changes in ovarian hormone levels [1]. As mentioned earlier, estrogen and progesterone levels increase in the luteal phase, increasing energy expenditure and causing an increase in food intake. In the follicular phase, with only increased estrogen levels, food intake seems to decrease. In addition, fluctuations in appetite, cravings, and energy intake during the menstrual cycle may occur in parallel with cyclical rhythms in serotonin, which might explain the accompanying affective symptoms like depression.

The relationship between food intake and hormonal fluctuation associated with the menstrual cycle is complex and involves several regulatory pathways. Further investigation is needed to better understand the exact mechanisms governing women’s dietary behaviors and energy levels throughout the month. Current research, however, highlights the importance of considering changes in eating habits during the menstrual cycle when interpreting the dietary assessments in women.

References

1. Kammoun, I., Ben Saâda, W., Sifaou, A., Haouat, E., Kandara, H., Ben Salem, L., & Ben Slama, C. (2017). Change in women’s eating habits during the menstrual cycle. Annales d’Endocrinologie, 78(1), 33–37. https://doi.org/10.1016/j.ando.2016.07.001
2. Stages of Menstrual Cycle: Menstruation, Ovulation, Hormones, Mor. (2018, August 17). Healthline. https://www.healthline.com/health/womens-health/stages-of-menstrual-cycle
3. Brennan, I. M., Feltrin, K. L., Nair, N. S., Hausken, T., Little, T. J., Gentilcore, D., Wishart, J. M., Jones, K. L., Horowitz, M., & Feinle-Bisset, C. (2009). Effects of the phases of the menstrual cycle on gastric emptying, glycemia, plasma GLP-1 and insulin, and energy intake in healthy lean women. American Journal of Physiology-Gastrointestinal and Liver Physiology, 297(3), G602–G610. https://doi.org/10.1152/ajpgi.00051.2009
4. Geary N. (2001). Estradiol, CCK and satiation. Peptides, 22(8), 1251–1263. https://doi.org/10.1016/s0196-9781(01)00449-1
5. Zhang, S, Osumi, H, Uchizawa, A, et al. Changes in sleeping energy metabolism and thermoregulation during menstrual cycle. Physiol Rep. 2020; 8:e14353. https://doi.org/10.14814/phy2.14353
6. Charkoudian, N., & Stachenfeld, N. (2016). Sex hormone effects on autonomic mechanisms of thermoregulation in humans. Autonomic neuroscience : basic & clinical, 196, 75–80. https://doi.org/10.1016/j.autneu.2015.11.004
7. Steward, R. G., Bateman, L. A., Slentz, C., Stanczyk, F. Z., & Price, T. M. (2016). The impact of short-term depot-medroxyprogesterone acetate treatment on resting metabolic rate. Contraception, 93(4), 317–322. https://doi.org/10.1016/j.contraception.2016.01.001