In part 1 one of this mini-carb-series, I busted some myths surrounding the effect of carbs on body composition. I also covered how consuming carbs doesn’t automatically turn you into a fat slob. And, of course, the main myth of how consuming less carbs yields superior fat loss was covered in detail and busted. In this sequel I will cover some harms low-carb diets have caused. So, without further ado, let’s begin. Hopefully this makes you fall in love with carbohydrates again!

#1) Slower Metabolism

A low-carbohydrates diet can and will affect your thyroid function directly and indirectly. The thyroid gland, located right below your Adam’s apple is largely responsible for how fast your metabolism is. Moreover, the thyroid gland is a major part of the endocrine system, and since all endocrine system’s parts are tightly connected, you can bet that any dysfunction that affects your thyroid will affect how well your endocrine system functions over all.

thyroid function

I don’t intend to turn this in a biology lesson, however, I must point out how the thyroid gland functions. As you can see in the picture above, the whole process starts when the hypothalamus produces Thyrotropin Releasing Hormone (TRH), which commands the anterior pituitary gland to produce Thyroid Stimulating Hormone (TSH). TSH, in turn, tells the thyroid gland to produce T4 (thyroxine) and T3 (Triiodothyronine) from dietary iodine. T4 is the inactive form while T3 is the active form. The thyroid gland releases thyroxine into the bloodstream which then gets converted into the more active form, T3, by the liver and kidneys (mainly by the liver). A normal level of T4 is not only essential for optimal levels of T3, but also to tell the hypothalamus and pituitary that everything is working well. You then have adequate levels of T3 than can bind to receptors all around your body (yes, there are T3 receptors all around the human body). As you can see, the process is not quite simple and any minor error during any of those steps will disrupt the whole process.

How does this relate to carbohydrates consumption?

Well, there are two main ways a low-carb diet can affect your thyroid function:

1) Inadequate iodine intake

2) Insufficient glucose levels

#1 – The thyroid gland mainly absorbs iodine, combines it with the amino acid L-tyrosine to make T3 and T4. Post the goiter endemic, most countries started enriching their flour and bread with iodine after discovering how important it is for normal thyroid function. Fortifying flour and bread with iodine rapidly and significantly decreased the rates of goiter all around the world. Additionally, since adequate insulin levels are mandatory for optimal conversion of T4 into T3, enriching flour and bread (simple carbs – glucose) with iodine was the perfect iodine delivery method. As a result, many countries still follow the same protocol to this day. Additionally, many countries also started fortifying sea salt with iodine, making “iodized salt”. Anyway, I am getting a little off track here. When you significantly decrease your carbohydrates intake, not only do you partially deprive your body of good levels of insulin (protein is also insulinogenic. Thus, circumstances differ) and consequently optimal conversion of T4 into T3 in the liver, but you also deprive your thyroid gland of the precious element iodine. Iodine is a naturally scarce element. Thus, unless you regularly consume seafood and use iodized salt, chances are you’re iodine deficient. The final outcome is sub-optimal levels of T4, T3, higher levels of rT3 (the inactive form of T3) and a slower metabolic rate. Not fun or healthy.

#2- The liver needs glucose to convert T4 to T3. During periods of low-carbohydrates intake, your body doesn’t have much glucose to normally carry out its functions. To top things off, whatever little glucose you have will be automatically conserved for your brain because the brain MUST have glucose!! Consequently, the process of converting T4 to T3 is put on hold or hindered, at least. The result is sub-optimal T4 and T3 levels and a slower metabolic rate. To add to the matter, even if you are consuming adequate amounts of iodine and L-tyrosine, and thus your thyroid produces adequate levels of T4, your body won’t be able to convert much of the available T4 into T3. So, where does the rest of T4 go? Reverse T3! Reverse T3, or rT3, is the inactive form of the hormone, T3. The result is usually Euthyroid Sick Syndrome, or, “healthy thyroid sick syndrome”, which is when your thyroid gland is perfectly fine but you have less than normal thyroid hormones. The consequence is usually “perceived” hypothyroidism, meaning, you experience all symptoms of hypothyroidism without actually having hypothyroidism.

 

Potential counterarguments

Gluconeogenesis

An individual might try to argue the second point mentioned above by stating that carbohydrates are not essential for human survival and that our bodies are capable of converting other macronutrients into glucose through a processed called gluconeogenesis. That might be true, but there are two problems with relying on gluconeogenesis to make adequate amounts of glucose; 1- It’s an inefficient process. 2- Ketone bodies! When a person decreases his carbohydrates intake to very low levels sufficient to induce ketogenesis, his body starts producing an alternative source of fuel called ketone bodies. However, ketone bodies are glucose-sparing, meaning, you still won’t have the adequate levels of glucose that your body needs to carry out certain glucose-dependent functions. More specifically, functions that primarily rely on glucose such as the conversion of T4 to T3. And since that person’s body is now relying on an alternative source of fuel (ketones), his body won’t see the need to convert much of the other macronutrients into glucose (gluconeogenesis). Thus, his body will produce just enough for the parts that solely rely on glucose such as the brain. Simply put, gluconeogenesis won’t result in adequate levels of glucose to fully convert available T4 to T3. It is true that ketone bodies can cover most of the body’s fuel requirements, but a bit of glucose is still required for certain functions. And although ketones can replace glucose for the most part, this doesn’t mean that functions that primarily rely on glucose will run just as well on ketones. A perfect example would be hepatic conversion of T4 to T3.

Total Caloric Intake

One of the counterarguments of low carbohydrates decreasing metabolic rate is  that individuals who decrease their carbohydrates intake often forget to increase their dietary fat intake to make up for the caloric deficit they created. Thus, what truly causes deregulation of the thyroid and thus metabolic rate should be attributed to consuming too little calories. This sounds good on paper, but studies say otherwise.

For example, these 3 studies concluded that after periods of being in a severe caloric deficit -enough to downregulate metabolism- refeeding with carbohydrates, but not with protein or fats, normalized thyroid hormone levels. 1, 2 and 3.

In another study, subjects were put on low calorie diets. The only difference between subjects’ diets was their intake of carbohydrates. Some consumed high carbs and some were put on low carbohydrates (2% of their energy intake). The researchers observed significant decreases in T3 in the low-carb dieters but now the high carb subjects despite energy intake being the same. Additionally, low-carb dieters also had significantly lower levels of T4 and higher levels of rT3. 

In is study, researchers put their subjects on 800-kcal diets composed of either 0%, 25%, or 100% carbohydrates for a period of 2 weeks. The researchers recorded significant decreases in T3 in both the fasting and low carbohydrates groups but not the high carbs subjects!

Admittedly, these studies have some limitations:

  • Small sample size.
  • Short duration.
  • Studies only included obese subjects, therefore, the results can’t be generalized to the rest of the population.

 

A Vicious Loop

If that wasn’t enough to emphasize some major problems that occur when you deprive your body of precious carbohydrates, allow me to introduce you to the “vicious loop”. It’s no secret that the number of patients with hypothyroidism in the U.S. (and other countries as well) has increased significantly over the past two decades. Or, has it?!! If you don’t see where I am going with this, allow me to elaborate.

If you made it this far into the article, you should know by now that low carbs result in inadequate levels of thyroid hormones and thus a hindered metabolic rate. Low carbs send a false signal to your body that food is scarce and that it should function as so. Since the human body is pretty smart, it’ll try to overcome this “food scarcity” by slowing down the metabolic rate to conserve energy and prevent you from starving to death. As part of the negative feedback loop illustrated in the picture above, the body will see that there are low levels of thyroid hormones and a high level of rT3 which all point to “food scarcity”. The hypothalamus sees that and sends a signal to the pituitary gland which in turn releases more Thyroid-releasing-hormone (TSH) in an attempt to “yell” at the thyroid to make more T4 and T3. The result is an elevated level of TSH. Since medical practitioners primarily base their diagnosis of thyroid disorders especially hypothyroidism on TSH levels, things become problematic.

The number of patients diagnosed with hypothyroidism has definitely increased significantly, but this is not an indicator that the number of people with actual hypothyroidism has increased! In other words, A LOT of people who think they have hypothyroidism don’t really have an underactive thyroid gland, however, they were simply misdiagnosed because of stupid dietary habits such as low carbohydrates, micronutrients deficiency, and a stupid TSH range that should supposedly act as the main and sole diagnosis tool.

Conclusion: Consuming low/zero carbohydrates will take its toll on your thyroid function as well as your health. But don’t worry because you get the bonus of your doctor potentially misdiagnosing you with hypothyroidism and putting you on medication. Congratulations, you’re an idiot! 🙂 If you don’t believe me, try and see for yourself (not recommended).

Good news: Before you freak out and cry out loud, the good news is that the thyroid gland is actually one of the most resilient body parts and has the ability to recover quite rapidly. A well-balanced diet that is mainly composed of whole foods and provides you with a good supply of all macronutrients and micronutrients will do you better than any other “diet” out there. Fix your diet, increase your carbohydrates intake, and increase your iodine intake and your thyroid will thank you.

#2) Hormonal disruptions

Cholesterol

People who consume very little carbohydrates often complain of having ultra-high cholesterol levels, which doesn’t really make any sense. A minor fluctuation would be fine, however, some individuals have complained of super high cholesterol levels. I won’t delve much into the matter since Paul Jaminet has written extensively about the topic here. So, check out that article if you are interested in the details. If you just want the summary: A low-carbs diet can send your cholesterol levels through the roof. And just like the case with false diagnosing hypothyroidism, you might be getting a blood test for a regular checkup and your results come back as dangerously high. The doctor could then put you on statins, which are one of the worst drugs one could take (generally speaking). This is emphasized because American doctors usually have no problems prescribing statins and antidepressants. Wonderful!

Cortisol

A low-carbohydrates has been demonstrated to elevate resting cortisol levels when combined with exercise. This mainly occurs because people on low-carbs usually don’t have enough glycogen stored in their muscles to cover their energy needs. As a result, during exercise, the body releases cortisol to break down muscle tissue in order to make glucose (gluconeogenesis). Moreover, low-carb diets result in overall low insulin levels. But, what does insulin have to do with cortisol? Well, it seems that insulin lowers cortisol levels (at least in obese subjects). Thus, insulin prevents cortisol from hindering testosterone production.

Low carbohydrates = chronically elevated cortisol levels = less testosterone levels.

Testosterone

Since cortisol and testosterone have an inverse relationship, one of them has to be low in order for the other to be high. If your cortisol levels are chronically high, your testosterone levels will plummet. Think of it as a system of checks and balances. As you can guess, a low carbohydrates diet can decrease testosterone levels by increasing cortisol levels (energy conservation) and by inhibiting serotonin and dopamine production.

Still not convinced? Let’s examine some studies together.

#1) Volek et al. had their resistance training subjects consume a diet either high in protein and low in carbs or the other way around. The researchers observed that subjects who consumed less carbohydrates had lower testosterone levels. In fact, subjects’ testosterone levels were dose dependent, therefore, the higher the protein to carbohydrates ratio, the less testosterone those subjects had. Total caloric intake was identical.

 

#2) Anderson et al. put their sedentary subjects on diets identical in both caloric intake and dietary fat. The only difference was the ratio of protein to carbohydrates. Not surprisingly, subjects on high protein and low carbs had significantly less DHT and testosterone levels than their high-carb mates. Additionally, the low-carb group also had significantly higher cortisol levels. Thus, it could be concluded that the high cortisol level was responsible for suppressing testosterone production.

 

Neurotransmitters

How much carbohydrates someone consumes has a direct and indirect effect on their neurotransmitters levels. Low carbohydrates consumption certainly decreases serotonin, GABA, and dopamine levels. I covered this extensively in the first part of this series.

 

#3) Stupid reasons

Lastly, some people rode the low-carbs wave for a myriad of stupid reasons. Here is a list of some of them:

  • Our ancestors didn’t eat carbs

Ummm, sorry to burst your bubble, but our great ancestors definitely ate carbs. They didn’t really have much of a choice, you know? Otherwise, they would’ve all died and, well, we wouldn’t be here either. They ate whatever the F*CK they could find! They just didn’t eat as much. Oh, and they didn’t really give a f*ck about being 8% body fat either LOL. They simply wandered around hunting and gathering food. They obviously didn’t have highly palatable foods and certainly didn’t consume as much food as we do in the western hemisphere. And btw, bread and rice date as far as thousands of years back! In fact, bread was a cornerstone food for many of the ancient civilizations. Anyway, as a result of general food scarcity and food availability, our ancestors had tons of carbs on certain days, moderate amounts other days, and little to any carbs when food was scarce. That’s it.

  • Carbs make you fat

No! -___- Eating too much makes you fat. In fact, de novo lipogenesis, conversion and storage of carbs as fat, is a complex and demanding process. However, high carbs in presence of a caloric surplus will yield weight gain. An abundance of any macronutrient during a caloric surplus will yield the same outcome.

  • Carbs aren’t essential

Just because a macronutrient isn’t essential doesn’t mean it’s best to eliminate it from your diet. All macronutrients play different roles in optimizing your health. I mean, why do 3 different macros exist if we only needed one? Essential doesn’t equal optimal.

  • Carbs aren’t delicious

Okay, now you’re just plain crazy. Dessert, anyone? Fruits, at least?

 

#4) More reasons why low-carb diets are stupid

Unnecessary restriction

I never understood why someone would feel the need to restrict him/herself needlessly! I mean, I respect personal preferences and believe that everyone should do whatever the hell they want, but why would someone refrain from eating something especially when it could do more harm than good?! I just don’t get it, but that’s just me ranting. Anyway, point is, restricting your carbohydrates intake is not harmful, but it’s also unnecessary. I give you permission to go have a chocolate mousse tonight, you’ll thank me late and tell me that you’ve been missing out unnecessarily.

Unsustainable

Generally, I don’t like the idea of being married to just one style of eating. I also don’t like the idea of being married to a few foods when there is a plethora of delicious and healthy foods everywhere, which is why I could never do traditional cutting phases and adopt a healthier and more flexible approach. Yes, a certain diet may work well but if it’s too restrictive, chances are you won’t be able to stick to it long term, and that’s absolutely fine. Same goes for low-carb diets, all the science and health stuff aside, I don’t think anyone could commit to having little to no carbs for the rest of their life. Instead, find a healthy balance and form your OWN eating style that suits your personal goals and psychology. Try looking at dieting and training as means for a goal, which is to be healthy and happy. Additionally, you get the bonus of looking good because we all want that too. Finding your own eating style will be far more sustainable than following some sort of “revolutionary” diet.

Note:  I almost forgot the myth that limiting carbs and consuming more dietary fats will make you burn more fat. Well, that’s kind of true, but guess what? Your body starts burning more fat BECAUSE YOU ARE EATING MORE OF IT! There is a huge difference between burning body fat and burning dietary fat. In the case of ketogenic diets, the latter is true, not the former.

Note 2: Another point to consider is that while the majority of the population will not respond well to low-carbohydrates based diets, a few individuals seem to do well on them. In fact, a rare breed of individuals will notice improvement in their performance when switching to ketogenic diets. However, the only logical reasoning behind this phenomenon is that those individuals are carb intolerant to start with. So, yes, ketogenic diets are better for certain individuals.

Conclusion

I hope this mini-carbs series helped you form some rational thoughts about carbohydrates and dietary habits in general. Form your own eating style that suits your lifestyle and psychology and you will achieve your goals and be happy and healthy. Don’t demonize one macronutrient because of what you heard or read online, instead, do your research, use critical thinking, and analyze things with an irrational and neutral mind and you will find the truth. Oh, and enjoy your food, please.

 

Published by Nour

My name is Nour Saber and I want to help YOU transform your body. With so much information and bro-science online, it could get tedious to find science-based and real world-proven information that can help you achieve the physique of your dreams. After years of learning and making the same mistakes you're probably making right now, I've decided to put together this FREE educational source to save you the time, hassle and frustration of finding practical and reliable information that is sure to put you on the right path.

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