Phase of the menstrual cycle affects insulin sensitivity – 09/24/2023 – Balance and Health

New study suggests that the brain reacts differently to insulin according to each phase of the menstrual cycle. The reaction has an impact on eating behavior and the entire metabolism.

Women, in general, know this experience well: every month, there comes a time when eating behavior seems to suddenly change. Sometimes this manifests itself as an increase in hunger, or a greater desire for carbohydrates.

The reason why many people want to eat chocolate during a certain period of the menstrual cycle has not yet been scientifically identified. But a research team from several German universities discovered that the brain reacts differently to the hormone insulin, depending on each menstrual phase. And such a reaction can have far-reaching effects.

Insulin acts directly on specialized nerve cells, thus regulating eating behavior and metabolism. It therefore plays a decisive role in weight control, in addition to controlling blood sugar in patients with type 1 diabetes.

The researchers, whose study was published this Thursday (21/09) in the journal Nature Metabolism, assume that the change in insulin sensitivity during the menstrual cycle influences several cognitive and metabolic processes that until now have not been investigated in a specific way for each sex.

Clinical trials need more diversity

From these results, it is clear “the importance of including women in clinical trials and paying attention to the progression of their cycles”, says Anke Hinney, who researches the role of genes in the development of childhood eating disorders at the University of Duisburg -Essen, and did not participate in the study.

“It seems trivial that the results shown would not have been achieved if only men had been observed. But this is precisely a core area of ​​gender medicine, to help improve understanding of the causes of disease in both sexes.”

In the study led by Martin Heni, a specialist in internal medicine, endocrinology and diabetology, researchers saw that the brain’s sensitivity to insulin varied during the participants’ menstrual cycle. In the follicular phase, which occurs before ovulation, the brain was very sensitive to insulin. In the luteal phase, after ovulation, the brain showed insulin resistance. In comparison, in normal-weight men, the brain’s sensitivity to insulin is generally constant.

“Thin women therefore behave like thin men in the first half of the cycle, while in the second half they apparently show insulin resistance, as seen before in overweight men,” says Alexandra Kautzky-Willer, head of gender medicine at Medical University of Vienna, which also did not participate in the study.

Phase of the menstrual cycle as a factor in research

In their randomized clinical trial, researchers examined 11 women throughout their menstrual cycle. In order to measure the brain’s insulin sensitivity, they were divided into two groups: one received a spray of the hormone through the nose; the other, a placebo. The results were then compared to another round of surveys of 15 more women.

According to the participants’ MRI scans, in the period before ovulation there was greater sensitivity to insulin in the hypothalamus, the central region of the brain for regulating hormones.

As the study involved only a small number of participants, more research is still needed before drawing definitive conclusions that can be applied to the treatment of diabetes or people with obesity. “It is very important that we take more into account the phase of the cycle, sex hormone levels and insulin sensitivity in future experiments, especially in metabolic and weight regulation research”, argues Kautzky-Willer.