Carbohydrates - Part 2
Carbs and Hormones
First, let’s define what a low-carb diet is:
Low carb diet = 30% or less of your food intake each day (the average diet hovers around 50 – 60%)
Low Carb and Cortisol
What research has found is that a diet too low in carbs or calories is a stressor and will increase cortisol.
My first thought was that maybe this is due to weight loss, as losing body fat too quickly can trigger the “oh no! Famine!!” response in the body. But, this boost in the stress hormone cortisol isn’t related to losing weight, studies have found that low-carb diets will trigger this cortisol boost, even without any weight loss.
It’s important to mention that perimenopausal bodies have higher cortisol levels due to low estrogen AND are much more sensitive to cortisol. So, add a low-cal or low-carb diet and now there’s A LOT of cortisol!
A major perimenopausal symptom is sleep problems and another is weight gain around the waist. Both of these symptoms can be triggered by high cortisol and it looks like managing cortisol levels during this major hormone upheaval is key. Keep this in mind if you try a low-carb diet to get rid of belly fat…it might just make it worse.
Carbs and Thyroid
The thyroid is highly affected by stress. The adrenals (that make stress hormones) and the thyroid need the same precursor to make their hormones, and the adrenals always get priority. If the adrenals need to make tons and tons of cortisol, then the thyroid doesn’t get to make as many hormones.
The thyroid works in the parasympathetic nervous system, or the “rest and digest” mode. It mainly helps to manage your metabolism (this is a big job). It determines how fast your heart beats, how warm your body is, how deeply you breathe, and whether you store or burn extra energy.
This issue of the adrenals getting priority is frustrating in the world we live in now, but it made sense for earlier humans where stress was rare. If there’s a major stressor, the body needs to prioritize staying alive now vs. taking care of long-term issues like healing wounds and fighting off viruses. Under stress your body also wants to conserve energy, just in case you need it later…so slowing down of your metabolism also makes sense. Now that stress is the norm, your poor thyroid is constantly getting depressed. It makes sense that hypothyroidism (low thyroid) has become increasingly common.
And, as we’ve just learned, a low-carb diet is a stressor, especially for women, and so that aspect alone may lower your thyroid function, especially if it’s followed for a long time.
But, that’s not it…
A low-carb diet also slows the conversion from T3 => T4. T4 is the active hormone, and less T4 = a slower thyroid. So, it’s not just that the thyroid has less hormone to work with (because the adrenals are stealing all of the precursors), there’s also a problem with conversion. The more that carbs are restricted, the more this occurs. This affects both men and women.
Study: https://pubmed.ncbi.nlm.nih.gov/11167929/
And, it looks like this is carb-specific (not just any low-cal diet). This study looked at two ULTRA low cal diets, one restricting carbs and the other didn’t, and the lower carb group had a bigger change in their T4 levels.
The good news! It looks like levels normalize when carbs are added back into the diet!
Study: https://pubmed.ncbi.nlm.nih.gov/97492/
And, this is because, um, maybe…the body needs carbs!
(for the record, if I was writing this in the low-fat 1980s and 1990s, I would be giving an impassioned plea for people to add fat back into their diet. Each macronutrient is VERY important, it’s just that carbs are the villains right now)
Low Carb and Menstrual Cycles
A women’s cycle is very sensitive to food intake and stress. If life is too difficult to sustain a pregnancy, it makes perfect sense that the body would do what it can to reduce the chance.
Humans are actually pretty unique in the animal kingdom. Many animals can pause or terminate a pregnancy if the environment won’t sustain it properly (not enough food, too much stress, etc). But, humans can’t, so a woman’s body needs to be sure the conditions are right before pregnancy.
As a teenager, I learned that if my body fat % goes down too much (around 13%) or if I over-exercise, then I’ll lose my period. But, it was never explained to me what was actually happening and we’ve learned a lot more in the 30 years since I last attended a high school sex-ed class.
We’ve learned since then that it’s not just famine-style issues that can cause period loss. Not eating enough carbs, even with a healthy body fat %, can cause this drop in hormones.
…and, it’s important to note that this loss of period isn’t just an “oh, no period this month”, there’s an orchestra of hormones that fall out of balance that cause this visible symptom.
It starts with a drop in the gonadotropin-releasing hormone, which starts the menstrual cycle. This results in a domino effect, causing a drop in the levels of other hormones such as luteinizing hormone, follicle-stimulating hormone, estrogen, progesterone, and testosterone.
Here’s something I found really interesting – the hunger hormone, leptin, does more than just affect our hunger, it also plays a role in fertility.
First, a bit on leptin:
Leptin is produced by your fat cells and also manages your appetite. If you have lots of fat cells, then your body produces lots of leptin, and that keeps you feeling more satisfied and less hungry. If your extra energy storage is low, then the low levels of leptin keep you famished. You're hungry all the time.
If you’re underproducing leptin, your body will drop your fertility hormones. This is more than likely related to the low body fat % = no period issue.
Could the vilification of all carbs be related to the higher rates of fertility issues in the last 20 years? The trouble is, we have no idea. There’s very little research on this.
One small study done in 2003 followed 20 teenage girls on the keto diet for 6 months and found that 45% had menstrual issues and 6 lost their period. Um…why haven’t any follow-up studies been done, especially with the extreme popularity of the ketogenic diet???
In Conclusion -
Carbohydrates are important for your body to work properly. To be clear, so are protein and fat, our body needs all three. The trouble is that we’ve spent over a century refining our carbs, which has led to a lot of the health issues we’re currently dealing with.
The solution to all of the glucose-related issues we’re dealing with isn’t to remove all glucose from our diets. It’s to go back to whole food forms and fix the deficiencies that were created by eating refined carbs (like chromium, magnesium, and b vitamins). It sounds almost too simple, but as someone who’s done this myself, it’s not as difficult as it seems :)
Now it's time for the Carb FAQs!
Got any questions or comments? Comment below, jump to our private Facebook Group, or the Ask Lisa page :).