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Keto & Carb Cycling: Personalizing the Keto Diet to Optimize Your Hormones

asthma, carb cycling

By Kelley Herring

The ketogenic diet is well known for its ability to promote fat loss. And if you’ve been reading my articles over the last few months, you also know about its numerous benefits for Alzheimer’s, PCOS, cancer, acne, traumatic brain injury, and more.

You probably also know that the keto diet is one that is very low in carbohydrates. Carbs are often considered “the enemy” when it comes to maintaining a state of nutritional ketosis.

But (as usual) the truth lies somewhere in the middle…

In fact, some research indicates that adding carbs to your diet – strategically – can actually help break through weight loss plateaus, balance hormones and make the keto diet work even better!

In this two-part article, you’ll discover:

  • The potential pitfalls of a long-term, low-carb diet

  • The unique cases that indicate more carbohydrates could be beneficial

  • The concepts of “keto cycling” and “carb cycling” and how they differ

  • The benefits of utilizing carb strategies, plus how and when to use them

  • Examples of keto and carb cycling, plus delicious meal ideas to get you started!

Potential Drawbacks to the Keto Diet

For many people, the first few weeks on keto can be a rough adjustment. This is especially true for those coming from a high-carb diet. The “keto flu”, as it is called, can bring an onslaught of unpleasant symptoms, including irritability, insomnia, brain fog, headaches, muscle soreness and more.

The good news is that these symptoms typically resolve in a couple weeks, as your body makes the switch from using carbohydrates to primarily using fat to produce energy.

However, for some people, restricting carbs too much – or for too long a period of time – can lead to other long-term issues. Let’s take a look at the potential hormonal drawbacks to long-term carbohydrate restriction.

Hormone Imbalances: T3, Cortisol and Leptin

Many hormones – including thyroid hormones, leptin and cortisol – are impacted by carbohydrates in the diet. And for some people, carbohydrate restriction can cause hormonal disruptions.

For example, women who adopt a very low-carb or ketogenic diet that contains too few calories – especially when these women lose too much weight and/or exercise excessively – may stop menstruating. This is known as hypothalamic amenorrhea and can indicate a need for more carbohydrates in the diet (or less exercise and more calories).i

Let’s look at the biochemistry behind carb restriction and how it can influence these important hormones…

T3: Triiodothyronine

In a previous article, I discussed the many benefits of a low carb or keto diet for thyroid issues, including autoimmune thyroid disease (Hashimoto’s).

The basis for this is pretty straightforward: Blood sugar dysfunction negatively impacts thyroid hormones and blood sugar balance is vital for healthy thyroid function.ii,iii,iv

However, long-term carb restriction can cause T3 thyroid hormone to drop.v And while this could be interpreted as worsening thyroid function, some experts believe it is an indication the body is becoming more sensitive to thyroid hormones. As less T3 is required to achieve the desired effect, the body decreases

Because we are all unique, the impact of long-term carb restriction on thyroid function will differ among individuals.

Are your thyroid antibodies going down on a low carb or keto diet? Do you have more energy and less brain fog? Is your weight stabilizing and your mood improving?

If so, these are good signs that your diet is working to optimize your health. On the other hand, if you feel lethargic and moody and see no improvements in thyroid antibodies, this may indicate you need more carbohydrates to optimize thyroid function.

post workout, workout, exercising, pcos, womens health, fertility

Cortisol: The Stress Hormone

The hypothalamic-pituitary-adrenal (HPA) axis a major control center that dictates how the body uses calories.vii And one of the key players is the corticosteroid hormone, cortisol.

Some research shows that fasting and a ketogenic diet can increase cortisol levels.viii But as we just discussed with thyroid hormones, this isn’t necessarily a bad thing.

In fact, while it is known as a “stress hormone”, cortisol has a number of benefits, including reducing inflammation and promoting fat loss. However, too much cortisol can actually have the opposite effects – boosting fat storage and reducing estrogen.ix This is because the corticosteroids both synergize and antagonize the effects of insulin.x,xi

Just like the thyroid hormones, the connection between keto and cortisol is complex and varied. Biochemical pathways are constantly in flux. For example, cortisol levels are affected by production. However, they are also impacted by clearance and regeneration (the process of converting inactive cortisone to active cortisol).

And because cortisol tests measure these elements differently and are simply a snapshot from a given moment in time, it can be difficult (and expensive!) to get a clear picture of the overall cortisol pattern.xii

What we do know is that metabolic syndrome is tightly linked with unhealthy cortisol patterns… and the keto diet is highly effective nutritional therapy for metabolic syndrome.xiii,xiv In fact, the keto diet has been shown to beneficially affect the cortisol pathways in people who are overweight with deep belly fat and markers for heart disease. xvAs Amber O’Hearn of states:

If the cortisol pattern that develops in response to a ketogenic diet were the kind associated with metabolic syndrome, we would expect people on ketogenic diets to show signs of abdominal fat gain, rising blood sugar, and worsening cholesterol profile. But we see the opposite. This makes it highly unlikely that ketogenic diets raise cortisol in a harmful way.”xvi

While the keto diet may beneficially affect those individuals struggling with metabolic syndrome and related issues, the case may be different for leaner people without these metabolic issues, and for women in different phases of their reproductive life.

If you’ve been on a carb-restricted diet for some time and are struggling with insomnia, symptoms of adrenal fatigue (HPA axis dysfunction), or poor recovery from exercise, strategically adding carbohydrates may improve your cortisol response and long-term health.

Leptin: The Satiety Hormone

Leptin is a hormone produced by your body’s fat cells. Often called the “satiety hormone” or the “starvation hormone”, leptin assesses your energy availability. If you have enough body fat, leptin tells your body it can burn calories normally.xvii

Leptin is also involved in reproductive function as females have leptin receptors in the ovaries. This makes sense because healthy reproduction is dependent upon energy availability. “Starvation mode” is a clear signal that a woman’s body cannot support a healthy pregnancy.xviii

As a woman, if you aren’t consuming enough calories or overly restricting carbohydrates, you could alter leptin’s ability to regulate your reproductive hormones. And because insulin stimulates leptin synthesis, this can further reduce leptin levels.xix

If you’re experiencing cycle-related issues on a very low carb or keto diet, this may indicate a need to add in a few more carbs.

carb cycling, sleep deprivation, stroke risk, exercise, all natural

The Case for Carbs: Personalizing Your Carbohydrate Intake

The full keto diet or a long-term very low-carb diet can be highly beneficial for most people. But it isn’t right for everyone at every stage of life. As you just learned, you may need to personalize your diet, depending on your unique biochemistry, activity level, and hormonal responses.

Here are some quick tips to guide your carb consumption.

You may need MORE carbohydrates if:

  • You are pregnant or breastfeeding

  • You lose your period or have irregular cycles (perimenopause)

  • You are highly active (especially with high-intensity workouts / heavy lifting)

  • You begin having trouble recovering from workouts

  • You have thyroid issues that seem to worsen on a carb-restricted diet

  • You have adrenal fatigue

  • You struggle with insomnia

  • Your body fat is very low

You may need LESS carbohydrate if:

  • You have brain-related disease like Alzheimer’s, Parkinson’s or traumatic brain injury (TBI)

  • You have PCOS, fibroids or endometriosis

  • You have yeast overgrowth, SIBO or other digestive issues, related to carbohydrate intake

  • You are diabetic or insulin resistant

  • You have cancer

Today, you’ve learned about the primary hormonal imbalances that can occur in some people on long-term carb-restricted diets. You’ve also discovered the symptoms and conditions that may indicate a need for more carbs.

In my next article, we’ll delve into the options for adding carbohydrates back into your diet strategically… how to plan your carb or keto cycling… plus some delicious, nutrient-dense sample meals to get you started.

Read more of Kelley Herring’s health & wellness articles on our Discover Blog.

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Kelley Herring is the author of the brand new book Keto Breads – which includes more information you need to know about why it is so important to avoid wheat and grains in your diet, plus how to use healthy replacements for these foods to create all the breads you love… without the gluten, carbs and health-harming effects. Click here to learn more about Keto Breads


i Meczekalski B, Katulski K, Czyzyk A, Podfigurna-Stopa A, Maciejewska-Jeske M. Functional hypothalamic amenorrhea and its influence on women’s health. J Endocrinol Invest. 2014;37(11):1049-1056. doi:10.1007/s40618-014-0169-3)

ii Kadiyala R, Peter R, Okosieme OE. Thyroid dysfunction in patients with diabetes: clinical implications and screening strategies. Int J Clin Pract. 2010; 64(8):1130-9.

iii Ruhla S, Weickert MO, Arafat AM, et al. A high normal TSH is associated with the metabolic syndrome. Clin Endocrinol (Oxf). 2010;72(5):696-701.

iv Ambrosi B, Masserini B, Iorio L,et al. Relationship of thyroid function with body mass index and insulin-resistance in euthyroid obese subjects. J Endocrinol Invest.2010;33(9):640-3.

v Pasquali R, Parenti M, Mattioli L, Capelli M, Cavazzini G, Baraldi G, Sorrenti G, De Benedettis G, Biso P, Melchionda N. Effect of dietary carbohydrates during hypocaloric treatment of obesity on peripheral thyroid hormone metabolism. J Endocrinol Invest. 1982 Jan-Feb;5(1):47-52. doi: 10.1007/BF03350482. PMID: 7096916.

vi Phinney, S. Does Your Thyroid Need Dietary Carbohydrates?  Virta Health. Published May 3, 2017.

vii Dallman MF, Strack AM, Akana SF, Bradbury MJ, Hanson ES, Scribner KA, Smith M. Feast and famine: critical role of glucocorticoids with insulin in daily energy flow. Front Neuroendocrinol. 1993 Oct;14(4):303-47. doi: 10.1006/frne.1993.1010. PMID: 8258378.

viii Ortiz RM, Wade CE, Ortiz CL. Effects of prolonged fasting on plasma cortisol and TH in postweaned northern elephant seal pups. Am J Physiol Regul Integr Comp Physiol. 2001 Mar;280(3):R790-5. doi: 10.1152/ajpregu.2001.280.3.R790. PMID: 11171659.

ix Geiker NRW, Astrup A, Hjorth MF, Sjödin A, Pijls L, Markus CR. Does stress influence sleep patterns, food intake, weight gain, abdominal obesity and weight loss interventions and vice versa? Obes Rev. 2018 Jan;19(1):81-97. doi: 10.1111/obr.12603. Epub 2017 Aug 28. PMID: 28849612.


xi Dallman MF, Strack AM, Akana SF, Bradbury MJ, Hanson ES, Scribner KA, Smith M. Feast and famine: critical role of glucocorticoids with insulin in daily energy flow. Front Neuroendocrinol. 1993 Oct;14(4):303-47. doi: 10.1006/frne.1993.1010. PMID: 8258378.

xii Purnell JQ, Kahn SE, Samuels MH, Brandon D, Loriaux DL, Brunzell JD. Enhanced cortisol production rates, free cortisol, and 11beta-HSD-1 expression correlate with visceral fat and insulin resistance in men: effect of weight loss. Am J Physiol Endocrinol Metab. 2009;296(2):E351-E357. doi:10.1152/ajpendo.90769.2008

xiii Stimson RH, Johnstone AM, Homer NZ, Wake DJ, Morton NM, Andrew R, Lobley GE, Walker BR.Dietary macronutrient content alters cortisol metabolism independently of body weight changes in obese men.

J Clin Endocrinol Metab. 2007 Nov;92(11):4480-4. Epub 2007 Sep 4.

xiv Vogelzangs N, Beekman AT, Milaneschi Y, Bandinelli S, Ferrucci L, Penninx BW. Urinary cortisol and six-year risk of all-cause and cardiovascular mortality. J Clin Endocrinol Metab. 2010;95(11):4959-4964. doi:10.1210/jc.2010-0192

xv Stimson RH, Johnstone AM, Homer NZ, Wake DJ, Morton NM, Andrew R, Lobley GE, Walker BR.Dietary macronutrient content alters cortisol metabolism independently of body weight changes in obese men.

J Clin Endocrinol Metab. 2007 Nov;92(11):4480-4. Epub 2007 Sep 4.


xvii Margetic S, Gazzola C, Pegg GG, Hill RA. Leptin: a review of its peripheral actions and interactions. Int J Obes Relat Metab Disord. 2002 Nov;26(11):1407-33. doi: 10.1038/sj.ijo.0802142. PMID: 12439643.

xviii Pérez-Pérez A, Toro A, Vilariño-García T, Maymó J, Guadix P, Dueñas JL, Fernández-Sánchez M, Varone C, Sánchez-Margalet V. Leptin action in normal and pathological pregnancies. J Cell Mol Med. 2018 Feb;22(2):716-727. doi: 10.1111/jcmm.13369. Epub 2017 Nov 21. PMID: 29160594; PMCID: PMC5783877.

xix Flier JS. Starvation in the Midst of Plenty: Reflections on the History and Biology of Insulin and Leptin. Endocr Rev. 2019 Feb 1;40(1):1-16. doi: 10.1210/er.2018-00179. PMID: 30357355; PMCID: PMC6270967.