The Immune, Gut, and Brain Reset Through Fasting

Recent research shows fasting can be a profound way to quickly and dramatically improve your immune, gut, and brain health. In our clinics we have many of our Hashimoto’s patients undergo different types of fasts because we have found it is one of the surest ways to swiftly relieve their symptoms.

Humans are actually built to withstand regular periods without food. The human body is not really equipped to cope with high-carbohydrate foods, sugars, unlimited supplies of food, processed foods, industrial oils, sedentary lifestyles, and other facets of everyday life for many Americans and westerners in general.

Five ways fasting improves your health when you have Hashimoto’s

Hundreds of studies point to the benefits of fasting. Five of these benefits include:

  1. Improved insulin sensitivity. Many, if not most, of our Hashimoto’s patients, have chronically high blood sugar. High blood sugar comes from eating a standard American diet, which is high in processed carbohydrates (bread, white rice, white potatoes, pasta, pastries, etc.) and sugars. High blood sugar eventually leads to insulin resistance, a condition in which the body’s cells refuse to receive insulin. Insulin carries glucose into the cells to be used to make energy. However, when you eat a diet high in carbohydrates and sugars, this overwhelms the cellular insulin receptors.

This not only creates fatigue after meals, it also dysregulates numerous metabolic pathways, promotes inflammation and autoimmunity, and speeds up degeneration of the brain. Insulin resistance is also a stepping stone to type 2 diabetes.

Including periods of fasting into your daily routine has been shown to help cells become more insulin sensitive. For instance, one study found restricting eating to a window of only 8 hours each day significantly improved insulin resistance.[i]

This in turn dampens the inflammation, metabolic imbalances, and brain degeneration caused by insulin resistance.

  1. Improved immune function. Intermittent fasting (fasting for 12–18 hours each day) has been shown to improve immune function by reducing inflammation and the damage from inflammation. It also regulates immune function (which is great for autoimmune diseases like Hashimoto’s), regenerates immune cells, and can even lower the risk of cancer.[ii]
  2. Improved brain function. Fasting and intermittent fasting can dramatically improve brain function. One way it does this is by boosting a brain chemical called brain-derived neurotrophic factor (BDNF). BDNF protects your brain from neurodegenerative diseases such as Alzheimer’s and Parkinson’s by supporting neuronal health. Fasting also supports autophagy or the removal of dead and dying cells in the brain. This is essentially like cleaning house and helps your brain function more efficiently. Fasting also reduces brain inflammation and supports brain repair.[iii]
  3. Improved cardiovascular function. Regular fasting can decrease low-density lipoprotein (LDL), or “bad,” cholesterol. People with Hashimoto’s often struggle with elevated levels of LDL and fasting is another tool to help lower it.[iv]
  4. Improved gut function. Many of our patients have leaky gut and poor gut immunity along with Hashimoto’s. Regular fasting helps them quickly and dramatically recover their gut health. Fasting has been shown to lower inflammation in the gut and create a healthier composition of gut bacteria.[v]

Fasting works its wonders by switching the body from burning glucose for fuel to burning ketones, which are stored in body fat. Being in ketosis in general appears to reduce inflammation, support regeneration, and regulate metabolism. These are all areas where people with Hashimoto’s can be supported by fasting.

Fasting is not for everyone

Before I explain the different types of fasts we use with our patients, I need to caution you that fasting is not for everyone. Although it can be an adjustment at first, fasting should make you feel better, not worse. You should be able to perform your usual daily activities.

Below are some situations in which fasting can make you worse instead of better.

Chronically low blood sugar. If you have chronically low blood sugar, do not try to fast until you can stabilize it. This means you may need to eat a healthy protein breakfast first thing in the morning and eat every two to three hours. You also need to avoid sweets, processed carbs, fruits, fruit juices, fruit smoothies, honey, and other sweeteners no matter how natural. Once your blood sugar is stable and you can longer periods without symptoms, you may be able to handle fasting safely.

Symptoms of low blood sugar include:

  • Waking up at 3 or 4 a.m. feeling anxious. This happens because your blood sugar crashes during the night and your body releases stress hormones to keep the brain fueled.
  • Waking up nauseous or repelled by the idea of food. Low blood sugar dysregulates appetite centers in the brain and the stress hormones released during the night to keep your brain fueled cause nausea.
  • Feel lightheaded, weak, nauseous, or irritable between meals or if you go too long without eating. This happens because your body cannot sustain your blood sugar levels.
  • Crave sugar constantly. Sugar provides energy, something people with low blood sugar crave.
  • Feel more energetic after eating. Eating should not give you more or less energy. Your energy should be consistent throughout the day. Feeling energetic after meals mean your blood sugar was low.

Adrenal autoimmunity

Some people are not able to regulate their low blood sugar no matter how hard they try. We find these patients often test positive for adrenal autoimmunity. The adrenal glands release stress hormones and are instrumental in preventing blood sugar crashes. If they are being damaged by an autoimmune disorder, you may not have success overcoming low blood sugar symptoms. In this case, it’s not advised to fast. You can test for adrenal autoimmunity with a 21-hydroxylase antibody test.

Some brain disorders

Although fasting and ketogenic diets have ample amounts of research showing they are very restorative of brain health, in his Kharrazian Institute Neuroinflammation course Dr. Kharrazian presented a case in which a brain trauma consumes so much of the patient’s energy that they are not able to fast without crashing and experiencing a flare-up of symptoms. If you have had a past brain injury or are struggling with brain health, you may need to use trial and error to see whether this is an issue for you. Fasting shouldn’t flare up your inflammation or your symptoms or cause a general worsening of health. It should make you feel better.

Diabetes medication

If you are on medication for diabetes, fasting could cause your blood sugar to go too low. You should consult with your doctor if you want to try fasting.

History of eating disorders/disordered eating

People with a history of eating disorders or disordered eating typically have a history of starving themselves for extended periods and may find fasting triggers them into bingeing, obsessive thinking about food, and other unhealthy behaviors. Although fasting has been shown to reduce cravings and appetite, human studies have been largely short-term, observational, and done on overweight middle-aged people. If the 6 to 8-hour feeding windows turn into uncontrollable feeding frenzies, or if fasting for one or more days is followed by days of bingeing, fasting is not healthy for you.[vi]

Pregnant or trying to become pregnant

Fasting is not recommended during pregnancy as the demands of pregnancy on the body are so great.

Six different types of fasting that can help improve your autoimmunity, gut function, and brain health

A variety of different methods of fasting exist today. Below I will go over six different fasting strategies that have been shown to be beneficial.

  1. Fasting once a week

In our office we suggest our Hashimoto’s patients fast once a week for 24 hours, drinking water with some Himalayan sea salt in it (this will help with adrenal function and electrolyte balance).

  1. Fasting once a month

If our patients are able to do so comfortably, we then ask them to fast for once a month for 36 to 48 hours. Again, we suggest our patients use Himalayan sea salt in their water.

  1. Fasting part of each day, or intermittent fasting

Perhaps the most popular form of fasting is called intermittent fasting. This entails fasting for 12–18 hours each day, starting in the evening, and ending the following day around lunchtime. The different types of intermittent fasting (IF) are as follows:

  1. 5:2 Fasting

This is one of the more popular IF methods. Eat normally for five days and then eat 500 calories for women or 600 calories for men on the two other days of the week. Choose whichever days you like to fast, but try and choose days where you won’t be overly active or stressed.

  1. Time-Restricted Fasting

Fast for 12–18 hours each day. Some experts suggest women do not fast more than 14 hours. This typically involves skipping breakfast and eating an early dinner; most of your time fasting is while you’re asleep. Even fasting only 12 hours overnight can you give benefits, although they won’t be as significant as longer fasts.

  1. Alternate-Day Fasting

Every other day eat 25 percent of your calorie needs, or about 500 calories. On the other days eat normally.

To learn more about Hashimoto’s and other factors that can cause hypothyroidism, read my book The Truth About Low Thyroid contact one of our wellness centers for more information.


About Dr. Redd

Josh Redd, MS, DABFM, DAAIM, is a chiropractic physician and author of the Amazon bestselling book The Truth About Low Thyroid. Dr. Redd owns seven functional medicine clinics in the western United States and sees patients from across the country and around the world who are suffering from challenging autoimmune, endocrine and neurological disorders. Dr. Redd also teaches thousands of health care practitioners about functional medicine and immunology, thyroid health, neurology, lab testing, and more.

[i] Saad R. Effects of Intermittent Fasting on Health, Aging, and Disease. N Engl J Med. 2020;382(18):1773. doi:10.1056/NEJMc2001176

[ii] Saad R. Effects of Intermittent Fasting on Health, Aging, and Disease. N Engl J Med. 2020;382(18):1773. doi:10.1056/NEJMc2001176

[iii] Longo VD, Mattson MP. Fasting: molecular mechanisms and clinical applications. Cell Metab. 2014;19(2):181-192. doi:10.1016/j.cmet.2013.12.008

[iv] Santos HO, Macedo RCO. Impact of intermittent fasting on the lipid profile: Assessment associated with diet and weight loss. Clin Nutr ESPEN. 2018;24:14-21. doi:10.1016/j.clnesp.2018.01.002

[v] Catterson JH, Khericha M, Dyson MC, et al. Short-Term, Intermittent Fasting Induces Long-Lasting Gut Health and TOR-Independent Lifespan Extension. Curr Biol. 2018;28(11):1714-1724.e4. doi:10.1016/j.cub.2018.04.015

[vi] Dalle Grave, R. (2020). Regular eating, not intermittent fasting, is the best strategy for a healthy eating control. IJEDO, 2, 5-7. doi:10.32044/ijedo.2020.02