Four reasons to think twice about a Ketogenic Diet

Updated: Apr 26

By Dr. Shawna Darou, ND and Dr. Emily FitzGerald, ND

It seems that everywhere you look online right now, people are promoting a ketogenic diet: for weight loss, energy, mental clarity and more. Yes, it’s true that most people will lose weight rapidly by cutting carbs, but are the rest of the claims legitimate? And what are the risks?

The ketogenic is a iso caloric diet that mimics the effect of fasting. It is low carbohydrate ( < 30 total grams per day) and burns fat as your primary fuel. Generally, macronutrients are consumed in the following percentages:

  1. 5-10% Carbohydrates

  2. 10-15% Proteins

  3. 75- 85% Fats

It’s important to note that not all low carbohydrate lifestyles are keto.

We wanted to share with you what we’re seeing clinically, and the potential risks of a ketogenic diet. As with all dramatic nutrition plans, there will probably be a 3-5% of people who thrive with this way of living for the long-term. This holds with most extremes, so there may be a few people reading this article who it doesn’t apply to but on the whole, we are seeing some concerning issues happen after following a ketogenic diet for more than 2-3 months at a time.

Four reasons think twice about a ketogenic diet

1. Restricting carbohydrates can stall ovulation

We are seeing significant onset of hormone imbalance in women starting a ketogenic diet, with irregular periods, skipped periods and irregular ovulation. In some women this is happening after just a couple of months of starting the ketogenic diet.

My friend and colleague Dr. Lara Briden is also seeing period issues with low-carb diet (, and speculates that women need at least 150 grams of carbohydrate to be able to ovulate and have regular periods, which is significantly higher than the 20-30 grams of carbs allowed on a ketogenic diet.

2. Low carb intake can affect thyroid function

With any type of dramatic food reduction, there is a risk of slowing down thyroid function, specifically the conversion of free T4 to free T3. The symptom of low thyroid function that we see most is hair loss, but it can also include constipation, dry skin, feeling cold all the time and getting more colds. What’s happening here is that you are slowing down your metabolism, and the body goes into storage-mode. This also happens with any form of prolonged high stress, calorie restriction and also over-exercising. The good news is that this effect is reversible once you adjust your nutrition, although it can take a few months to normalize again.

3. Rebound weight gain

Since the ketogenic diet is so dramatic and highly restrictive, many people find it hard to stick with it consistently. And with any restriction comes a physiological urge to overeat. Any restriction followed by a binge results in the classic yo-yo weight fluctuation and rapid fluctuations in weight are actually associated with increased mortality.

Diversity in the diet is incredibly important and you may grow tired of the restricted nature of the ketogenic approved foods.  Not only that, you may be incurring some serious micronutrient deficiencies.

Further in a study comparing the low carbohydrate ketogenic (KLC) diet with a non-ketogenic low carbohydrate (NLC) diet containing a similar amount of protein and 40% of calories coming from carbs no metabolic advantage was seen, meaning weight loss was identical with each nutrition plan. In fact, inflammatory risk factors were more adversely affected by the KLC than by the NLC diet.

4. Possible Increased risk factors for cardiovascular disease and breast cancer

Eating very high fat, and especially lots of saturated fats has been associated with increased risk of cardiovascular disease. In spite of positive changes in fasting insulin levels, HDL cholesterol and blood pressure which should indicate lower cardiovascular risk, there are some troubling findings in ‘small artery vascular reactivity’ and something called “FMD” (flow-mediated dilation) which is a marker of endothelial function, which plays a major role in destabilization of atherosclerotic lesions and cardiovascular events. Based on these risk factors, studies are showing an increased risk of cardiovascular events (1, 2).

Similarly, a high-fat, especially high saturated fat diet is associated with an increased risk of breast cancer (3, 4, 5).  A ketogenic diet also limits foods that are known to help protect against cancer: fruits, whole grains, beans, and includes animal proteins which boost IGF-1 (insulin-like growth factor 1), which has been associated with increased cancer risk especially for breast and prostate cancer (6, 7, 8).

A few conditions where Keto might be the right choice

The ketogenic diet did come from clear evidence for a few health conditions, so there are a couple of good reasons to consider it, especially with neurological conditions. Here are some of the conditions with clear evidence supporting a ketogenic diet:

  1. Epilepsy

  2. Certain cancers, especially brain cancer (glioblastoma multiforme (GBM))

  3. Parkinson’s

  4. GLUT1 deficiency syndrome

  5. Certain subtypes of Alzheimer’s disease


  1. Epilepsy:

  2. Cancer:;year=2009;volume=5;issue=9;spage=7;epage=15;aulast=Seyfried,

  3. Parkinsons:

  4. GLUT 1 deficiency syndrome:

  5. Alzheimer’s Disease:

  6. Powerpoint: Ferretti, Alessandro. Ketogenic Aids in Health. Retrieved from Equilibria-SHEICON15-KD-and-KAD-Sept-15

Cautions with implementing a ketogenic diet

  1. Execution – The execution is very important. Ketogenic diets are not something that you consider doing from Monday to Friday. They are not an on and off approach. When you do not commit to it, you could see a large spikes in your lipid profile.

  2. Keto acidosis: When ketones are above 10mmol/L and high blood glucose at the same time. This can cause malaise, low energy, dehydration and thirst and is potentially lethal.

  3. Sodium Depletion: When insulin drops as a result of the low carbohydrate diet, the retention of salt from the kidney decreases dramatically. Make sure to properly replace sodium in the diet and track electrolytes.

  4. Gastrointestinal Symptoms:  High dietary fat intake and low fibre could negatively affect the microbiome by lowering the diversity of gut microbes. It’s important to include fermentable fibers like resistant starch to support the microbiome in your gut.

The argument for individualized nutrition

If you’re looking at the ketogenic diet as a way to optimize weight loss, for mental clarity or for physical performance, we would highly recommend that you consider your personal nutrition needs. An individualized nutrition plan can be developed for you based on many factors:

  1. Blood sugar metabolism and presence of insulin resistance

  2. Current and past stress levels

  3. How much you exercise and the type that you prefer

  4. Presence of allergies or autoimmunity

  5. Your blood type

  6. Your hormone balance (estrogen dominance, low thyroid, adrenal stress, etc)

  7. Your family history risk factors (cardiovascular disease, cancer, neurological disease, autoimmunity, etc)

  8. Your current health issues

  9. Your food sensitivities

  10. Your genetics

Your optimal nutrition needs to be personalized to you as an individual. There really is no one-size-fits-all approach.

The bottom line

Overall, we’re not a fan of dramatic diet plans especially ones that are not sustainable for the long-term. They feed into ‘diet-mentality’ which never works. Whenever you lose weight rapidly through a dramatic diet change, you are extremely likely to regain it all back and more. The reason there are so many varied nutrition plans out there is because there are so many varied nutritional needs – it is most important to find a way of eating that works best for you over the long-run.

What’s Next?

Book an appointment online. Contact us: 416.214.9251,


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