• Premenstrual food cravings affect many people, and a new study suggests they might be a result of decreased insulin sensitivity.
• High insulin sensitivity allows the cells of the body to use glucose more efficiently, lowering blood glucose levels.
• The study has found that insulin sensitivity varies throughout the menstrual cycle, being the highest before ovulation and lowest in the days preceding a menstrual period.
• The researchers suggest this could explain why many women feel much hungrier just before their period.

Craving chocolate and carbohydrate-rich foods in the days before a menstrual period, resulting in weight gain, is common in many people who menstruate.

New research, recently published in Nature Metabolism, has found that insulin sensitivity — the response of your cells to the hormone insulin — varies throughout the menstrual cycle, being the highest in the days before ovulation and lowest in the run-up to a menstrual period.

The researchers suggest their findings explain why so many women experience hunger just prior to getting their period, why their metabolism slows, and why weight gain is so much more likely.

“This is an interesting finding — diabetics have reported cyclical changes in their blood sugar management for many years […] It is great to see some research into this at last!”
— Sally King, founder of Menstrual Matters, fellow in menstrual physiology, Dept. of Women and Children’s Health, King’s College London, who was not involved in the study.

However, Dr. Kara McElligot, obstetrician-gynecologist, NAMS-certified menopause practitioner, and medical advisor at Mira, who was not involved in the study, cautioned: “This is an exploratory observational study that provides some compelling pilot information. A study of this level can suggest possibilities but not prove that the conclusions are true.”

“The methodology of this study was too limited to definitively conclude that insulin sensitivity is reduced during the luteal phase of the menstrual cycle,” she added.

How hormone changes and menstruation impact insulin

The menstrual cycle is controlled by hormones, which increase and decrease throughout the cycle. And this study suggests that these reproductive hormones may also affect insulin sensitivity.

The researchers measured insulin sensitivity in the brains of women who had a natural, healthy menstrual cycle during different phases of their menstrual cycle. They administered insulin via a nasal spray and measured the response of the hypothalamus during both the follicular (the days before ovulation) and luteal (the lead-up to the menstrual period) phases of the menstrual cycle.

Previous studies have shown inconsistent results about changes in blood glucose levels. However, a recent study has shown that blood glucose levels peak in the luteal phase (just before the period) and are at their lowest just before ovulation. And higher food cravings occurred when the blood glucose levels were highest.

Altered insulin sensitivity

The researchers found that in lean women, brain insulin action improved peripheral insulin sensitivity during the follicular phase but not in the luteal phase.

Commenting on the findings in an accompanying Nature Metabolismarticle, Prof. Dr. Nils B. Kroemer suggested: “this study raises the intriguing possibility of a central role (both figuratively and literally) of insulin signaling in the brain in orchestrating metabolic adaptations during the menstrual cycle.”

He suggests that the reduced insulin sensitivity in the premenstrual phase could help explain the food cravings and changes in appetite and body weight experienced by many people at this time.

The study was carried out in only 11 women, so the researchers caution that more research is needed to confirm their findings.

And Prof. Kroemer agrees that more research should “evaluate whether metabolic changes during the menstrual cycle may help to explain altered behaviour, including shifts in mental and physical health more broadly.”

Why insulin sensitivity is important

The hormone insulin controls the level of glucose (sugar) in the blood. Insulin is a chemical messenger that makes cells absorb glucose from the blood, giving them energy to function.

Insulin sensitivity describes how efficient this process is. High insulin sensitivity means that glucose is transferred into the cells effectively. Low insulin sensitivity, or insulin resistance, occurs when the cells do not respond well to the hormone, so glucose stays in the blood.

This results in increased blood glucose levels and cells being deprived of energy. This can lead to prediabetes, a condition that may increase the risk of developing type 2 diabetes.

This small study found that in those without prediabetes or diabetes, brain sensitivity to insulin is influenced by the menstrual cycle.

Sweet cravings before a period

“A state of reduced insulin sensitivity during the luteal phase of the menstrual cycle would, in theory, increase appetite.”
— Dr. Kara McElligot

In the premenstrual phase, both progesterone and estrogen levels decrease, and this is when desire for sweet foods is most likely. Previous studies in people with type 1 diabetes have suggested that estrogen increases insulin sensitivity.

“From an evolutionary perspective, by increasing the amount of glucose circulating in the system during the luteal phase, the body would be better able to compensate for energy loss related to pregnancy (or menstruation) that follows,” Dr. McElligot said.

“In comparison, females without the change in insulin sensitivity and regulated appetite could be at a disadvantage in times of food shortage and therefore less likely to successfully reproduce,” she added.

Adapting diet and exercise to menstrual phases

Past studies have shown that people tend to vary what they eat depending on the stage of their menstrual cycle. That premenstrual desire to carb load, which may be accompanied by weight gain, is widespread.

But the good news is that studies suggest weight is often gained in the premenstrual days, but people generally lose some around ovulation, meaning there is little overall change.

Şebnem Ünlüişler, genetic engineer at the London Regenerative Institute, who was not involved in the study, said that such changes in insulin sensitivity during the menstrual cycle could impact metabolism and weight, advising that “Women might find it beneficial to adapt their diet and exercise routine according to their menstrual phase.”

“These studies highlight the intricate relationship between hormonal fluctuations and metabolic health in women. Understanding these dynamics may lead to more targeted interventions for managing appetite, weight, and overall health during the menstrual cycle,” she added.

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