- The brain reacts less to insulin in the premenstrual phase of the female cycle
- This could also help explain premenstrual mood swings, experts say.
Women who feel hungry and crave chocolate and chips every month have good reason.
A study has found a change in women’s brains at a certain time of the month that could affect their appetite and desire for junk food.
Researchers found that in the premenstrual phase of a woman’s cycle, after ovulation but before her period arrives, a region of the brain called the hypothalamus reacts less to the hormone insulin.
Most people know about insulin, which is produced by the pancreas, in relation to diabetes because it regulates blood sugar.
But when insulin reaches the brain, previous evidence suggests it can make women less hungry and more likely to snack.
The brain reacts less to insulin in the premenstrual phase of the female cycle, which could cause women to crave chocolate and chips at certain times of the month.
Therefore, the new finding that insulin does not work as well in the brain when women are premenstrual could help explain their increased appetite and unhealthy cravings at this time.
The findings come from scanning the brains of 15 women in an MRI machine.
Lead author Professor Martin Heni, who led the study at the University of Tübingen, Germany, said: “There is not as much research on insulin in the brain as there is in the body.
‘This is the first evidence that it has less effect on women at a certain point in their menstrual cycle.
“The implication that this could help explain hunger and cravings in premenstrual women is really helpful: it shows that women who struggle with this are not getting it back.
“However, our study did not directly examine these effects in women.”
The study, published in the journal Nature Metabolism, gave 15 women a nasal insulin spray to mimic what happens when the hormone reaches the brain.
This triggered significant activity in a brain region called the hypothalamus during the “follicular” phase of her cycle, from the day after her last period until ovulation.
But there was less brain activity in the “luteal” phase, when women are premenstrual, after ovulation but before their period.
This could also help explain premenstrual mood swings, since the action of insulin in the brain can affect emotions.
Researchers suspect that women need insulin in the first half of their cycle, as the hormone controls glucose in the body, so it can recruit energy to help them produce an egg and thicken the lining of the uterus in case there are any leftovers. pregnant that month.
But this process is less necessary after ovulation.
However, the lack of insulin sensitivity seen in the brain of premenstrual women is independent of the lack of insulin sensitivity seen in the rest of the body, which can lead to type 2 diabetes.
It means that women should not fear a significant rise in their blood sugar level in the second half of their menstrual cycle.
However, a temporary lack of insulin sensitivity in the brain could, over decades, contribute to more fat being stored in the body.
It means that women’s premenstrual brain changes could be one of the reasons why they generally have more body fat than men.