It seems like each year there is a new rule in eating. Suddenly all the old rules about food fly out the window and everything we have ever known is replaced by new things—which will, of course, be replaced by newer, new things in a few years.
It can be hard to navigate what’s actually healthy and what’s a fad diet, especially when there is so much conflicting information out there.
So today, we want to clear up some of the confusion, particularly around one of the most popular current food trends: low carb diets. We’ll take an honest look at how this style of eating may impact your hormones, physical health, mental health, and sleep.
What are low carb diets?
There are several different types of low carb diets currently circulating: the keto diet, Atkins diet, the “Zero carb” (AKA carnivore) diet, a few versions of the paleo diet—and each one of these has different carb requirements.
Generally, “low carb” describes diets that include a maximum of 20 to 50 grams of carbs per day. For reference, one banana has about 28 grams of carbs. These sorts of diets tend to limit grains, starchy vegetables, and fruits, and instead focus on fats and proteins. This way of eating can cause the body to use fat as fuel instead of glucose (carbs), i.e., force your body into a state of ketosis.
While this way of eating has been shown to help people with epilepsy, certain neurological conditions, Type 2 Diabetes, metabolic syndrome, and some heart diseases, experts warn that the keto diet should be treated as a medical diet, and that extremely low carb diets are not without side effects.
This seems to be especially true for women.
Does low-carb mess with hormones?
First of all, any diet that is severely restrictive in calories can disrupt female hormones. This is because inadequate calories and nutrients can impact the hypothalamic-pituitary-adrenal (or HPA) axis. This mouthful of a phrase describes the complex interaction between the hypothalamus, pituitary, and adrenal glands, which keep hormones in balance.
Let’s say you’re on a low carb diet and getting plenty of calories through fats or proteins. Would this still impact your hormone levels?
Research says, probably.
Low carb diets tend to increase levels of cortisol compared to diets that are moderate-fat and moderate-carb. Cortisol, a stress hormone, can impact the HPA axis. This can cause a whole domino effect of hormonal dysregulation, and for some, may cause amenorrhea (the loss of your period for three months or more).
This is especially true for women who are active. Whether we like it or not, carbs are the body’s preferred source of energy. When athletic women consume too few carbohydrates, it puts the body into a stress response, which can affect menstruation and other important metabolic processes. This increase in cortisol may even cause weight gain, rather than loss; which is probably the opposite of what you’re trying to get a low carb diet to do.
One more study to further drive this point home: Several years ago, researchers looked at a group of 20 young women who were eating a very low carb diet to help treat their epilepsy. During the six month study period, 45 percent of the girls experienced irregular periods, menstrual problems, or amenorrhea—even those who did not lose weight. After the study was over and they reintroduced carbs, their periods returned to normal.
This is why it’s important to eat more carbs during certain times of the month.
Does low-carb impact physical health?
A very low carb diet can be bad for your bones, and as women, we need all the bone health help we can get. A 2019 study looked at how diet and exercise impact bone health in athletes. Ultimately, they concluded “[high fat and low carb diets] may be detrimental to bone mineral density and bone strength, with major consequences to health and performance.”
Active women who follow a low carb diet are also more likely to become anemic. This type of diet increases inflammation levels post workout, compared to a higher carb diet. This makes it harder to absorb iron, and women already have higher rates of anemia than men.
Additionally, healthy carbohydrates like fruits, vegetables, and grains are our primary fiber sources. A diet low in fiber can have a hugely negative impact on your digestion and gut—it’s no wonder constipation and diarrhea are common side effects to low carb diets.
Does low-carb impact mental health?
Many researchers have found that very low carb diets tend to impact mental health, especially in women. This is for a number of reasons:
Carbs create serotonin
Healthy carbs increase levels of tryptophan, which is converted into serotonin, AKA “the happiness hormone.” Low carb diets tend to lead to lower levels of serotonin.
High protein creates more adrenaline
Where carbs increase levels of serotonin, protein increases levels of tyrosine, the amino acid that creates adrenaline. So a diet that is high in protein but low in carbs may mean lower serotonin and higher adrenaline. Sounds like a truly terrifying combination.
Lack of nutrients
Healthy carbs like fruits, vegetables, and whole grains are rich with important nutrients, and it’s important to get a healthy variety of these things to reduce levels of stress.
Lower carbs = more cortisol
As we mentioned, low carb diets can create more of the stress hormone, cortisol—especially for athletes. Higher levels of cortisol can mean higher levels of anxiety, mood swings, panic attacks, and other mental health issues.
Gut health
The fiber found in healthy carbs can positively impact your gut health. Since mental health starts in the gut (where most of your serotonin is produced), keeping your gut healthy and happy is vital.
Carbs regulate hormones
Like we said, carbs help regulate female hormones. When our hormones are out of whack, it can cause anxiety, depression, and mood swings.
Does low-carb impact sleep?
Carbohydrates increase levels of tryptophan in the brain, which are converted to serotonin, which at night, is then converted into melatonin, the sleep hormone. Research shows that diets low in carbohydrates can decrease levels of melatonin, and cause insomnia.
This, plus the adrenaline created by higher levels of protein may mean some sleepless nights. And don’t women already have enough issues with sleep?
Who should not do a low carb diet?
If you’re on a low carb diet and you feel healthier than ever, your periods are regular (if you are premenopausal), your sleep is great, and your mental health feels stable, then more power to you. These diets may be beneficial for certain populations, including those with epilepsy, diabetes, obesity, or those who live a very sedentary lifestyle.
However, for those who live a more active lifestyle, research tells us we need at least some carbs, or else our physical health, mental health, and sleep can be negatively impacted. This is especially true for women since (healthy) carbs play a vital role in hormonal regulation.
Not all carbs are created equal
Of course this doesn’t mean we should shovel pastas, pizza, and cookies everyday, because not all carbs are created equal. Harvard’s School of Public Health says refined carbs (white flour), sodas, candies, and processed food should be nixed (though we say treat yourself, in moderation) and instead, we should focus on getting a moderate amount of complex carbohydrates rich in nutrients and fiber. These include fruits, vegetables, and healthy whole grains. Healthy complex carbs plus lots of leafy greens, healthy fats, and plenty of lean protein, should provide your body with high quality fuel for hormonal regulation, mental health, physical health, and sleep.
If all else fails, trust your intuition*.
*Unless your intuition is just saying “cheese fries, 24/7.” Then maybe trust the Mediterranean diet.
