- The brain responds less to insulin in the premenstrual phase of a woman’s cycle
- This could also help explain premenstrual mood swings, experts say
Women who feel hungry and crave chocolate and chips every month have a really good reason for this.
A study has found that at some point during the month, a change occurs in women’s brains that can affect their appetite and cravings for junk food.
Researchers found that in the premenstrual phase of a woman’s cycle, after ovulation but before her period arrives, an area of the brain called the hypothalamus becomes less responsive to the hormone insulin.
Most people are aware of insulin, which is produced by the pancreas, in connection with diabetes because it regulates blood sugar levels.
But when insulin reaches the brain, previous evidence suggests it can make women less hungry and more prone to snacking.
The brain responds less to insulin in the premenstrual phase of a woman’s cycle, which can 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.
Senior author Professor Martin Heni, who conducted the research at the University of Tübingen in Germany, said: ‘There is not as much research into insulin in the brain as in the body.
‘This is the first evidence that it has less effect on women at a certain point in the menstrual cycle.
‘The implication that this could help explain hunger and cravings in premenstrual women is very useful; it shows that women who struggle with this aren’t making it up.
‘However, our study did not directly look at these effects in women.’
The study, published in the journal Nature Metabolism, gave the 15 women a nasal spray containing insulin to mimic what happens when the hormone enters the brain.
This caused significant activity in an area of the brain called the hypothalamus during the ‘follicular’ phase of their cycle – from the day after their 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, as the action of insulin in the brain can influence emotions.
Researchers suspect that women need insulin in the first half of their cycle because the hormone controls glucose in the body and can recruit energy to help them produce an egg and thicken the lining of their uterus in case they do. month pregnant.
But this process is less necessary after ovulation.
However, the lack of insulin sensitivity in the brains of premenstrual women is separate from the lack of insulin sensitivity in the rest of the body, which can lead to type 2 diabetes.
It means that women do not have to worry about a big increase in their blood sugar levels in the second half of their menstrual cycle.
However, the temporary lack of sensitivity to insulin in the brain can contribute to more fat being stored in the body over decades.
It means that the premenstrual changes in women’s brains could be one of the reasons why they generally have more body fat than men.