Why I Won’t Coach Clients Through Intermittent Fasting and Low Carb Diets
These trendy diets are a huge no-go for autoimmunity and adrenal dysfunction.
First things first, let me be clear in saying that I don’t think a low carb diet or some moderate fasting can be helpful in certain situations. Like everything in the world of nutrition, this is a nuanced topic. But in general, individuals who already experience HPA axis dysregulation, or who lead a high stress lifestyle, should likely be avoiding low carb diets like Keto, as well as intermittent fasting (IF). The same goes for those with an autoimmune condition, as adrenal dysfunction is usually a piece of the autoimmune puzzle.
We’ll get to all the good reasons on why in a minute. Before we do, we need to clarify some terms being used. For the purposes of this article, Intermittent Fasting (referred to from here forward as IF because it’s just so much easier) is partaking in fasting at least 5 days a week, with each fasting period being longer than 14 hours. For example, if you eat your last meal of the day at 6pm, and eat breakfast by 8am the next day, we won’t consider that fasting. However if you are consistently eating your last meal at 6pm, but not eating breakfast until 10 or later, for our purposes this would fasting. It’s important to keep this in mind as there are so many different techniques and time periods of fasting.
We also need to define what exactly a low carb diet is. A true Ketogenic diet, where one is actually in ketosis, would be considered low carb- this usually means getting less than 20g of net carbohydrates per day. Net carbs are simply carbohydrates minus fiber, and this can wind up being anywhere between 50-75 ish g of carbs per day. Any other low carb diet would be considered eating less than 100-120g of carbs per day for most adults. When someone says they are “low-carb” I always ask, relative to what? A ketogenic diet, or a Standard American Diet? Individuals eating a Standard American Diet (SAD) can easily consume upwards of 350g of carbohydrates per day- and usually from less than ideal sources, such as cereal and candy. Relative to the SAD, most health conscious individuals are likely “low-carb”.
Not everyone is low carb on purpose- many of my clients come to me on AIP or Paleo type diets and when we analyze their food logs, discover they are barely getting 80-100g of carbs a day. When higher carbohydrate food groups like grains and legumes and even dairy are fully eliminated, it can actually be quite difficult to get enough carbohydrates in the diet. It doesn’t help that many health conscious individuals are also scared to eat fruit, as it’s been likened to being just as bad as refined cane sugar (no, it’s nowhere close)!
What are the negative effects of low carb and IF diets?
The number one issue with both fasting and low carb diets is that they have been shown to raise cortisol. It’s worth pointing out that many who participate in IF are also very low carb, whether they mean to be or not. Double whammy!
The issue with chronically raising cortisol is that it in turn affects many biological processes in the body. It is part of our diurnal or circadian rhythm, which affects sleep and wake cycles. Studies show that the longer a fast, the higher cortisol is raised (1). This can lead to a decreased production of melatonin, which is our sleep hormone, and is produced in the evening, but not if cortisol levels are high at that time.
Cortisol also affects sex hormone production- specifically testosterone and estrogen. When cortisol is elevated all the time, the body reduces its production of both of these hormones. While we often associate testosterone as being important for men, it is also important for women to have sufficient levels. Low testosterone can lead to low libido or sex drive, infertility, decreased muscle mass, fatigue, muscle weakness, and mood changes. Low estrogen can cause deposition of fat around the midsection- this is why we link high cortisol to increased waist size- and also causes symptoms like night sweats, insomnia, and mood swings (3).
Serotonin levels are reduced when cortisol is high as well (4). Serotonin not only affects our mood, but it is a precursor to melatonin production. Without enough serotonin, symptoms of moodiness and insomnia will prevail. This is one reason why chronic stress doesn’t always show as anxiety and feeling anxious but rather as depression.
Fasting and low carb diets raise cortisol
High cortisol reduces estrogen
High cortisol reduces testosterone
High cortisol reduces serotonin
High cortisol reduces melatonin
Cortisol isn’t the only hormone affected by fasting.
Cortisol isn’t the only hormone that has been shown to be affected by fasting. Insulin and triiodothyronine, or T3, also follow diurnal rhythms, much like cortisol, and are also highly affected by fasting. The longer the fast, the lower the insulin levels, the lower the T3 levels, and the higher the cortisol levels. Let’s break down why each of these may be an issue.
Many people try IF in order to reduce insulin levels. If your fasting insulin is indeed high, this can potentially be a helpful modality to utilize. However if your insulin levels aren’t high, constant fasting can actually drive them in that direction due to high cortisol levels. Chronically raised cortisol is associated with lowered pancreatic response mechanism that leads to a reduction of insulin sensitivity- in essence, leading to insulin resistance (5).
Triiodothyronine, or T3, is the thyroid hormone used by the tissues of the body. It controls metabolism, body temperature, bone health, brain function, heart function, and digestion. Fasting reduces the levels of circulating T3 in the body (1). In addition, elevated cortisol levels reduce the conversion of T4 to T3, further lowering the levels of T3.
We are often already in a state of chronic stress.
Most of us exist in a state of chronic stress. This is due mostly to a mismatch between our genetics and the lifestyle we all currently lead. Sadly, there is not much we can do about that part if we want to exist in our current world. However, we can certainly learn to manage our stress and stress hormones through a myriad of interventions. One of these is to become educated about how our dietary patterns affect our cortisol levels.
If you live a high stress lifestyle and already exhibit symptoms of elevated cortisol or adrenal dysfunction in general- low libido, insomnia, skin issues, weight gain, brain fog, headaches, GI issues, blood sugar dysregulation, depression or anxiety- avoiding trendy diets like low-carb and IF is recommended. Instead, focus on consuming a moderate carbohydrate diet -between 130 and 250 g a day- and find ways to reduce your stress levels.
Looking for guidance and accountability on lowering your stress levels? Check out my Stress Less in 12 Weeks Program!