The 9 Dangerous Side Effects of a Low-Carb Diet

low carb diet side effects

According to the Institute of Medicine and nutritionists, 45-65%, i.e. 225-325g of the daily 2000 calorie requirement should be consumed from carbohydrates. While a traditional low-carb diet reduces this amount to 60-130g, a ketogenic diet takes it even lower to only 30g a day. This minimal carbohydrate intake forces the body to use stored fat as fuel (ketosis).

However, a drastic carbohydrate deficiency, when continued for the long-term, can result in numerous physical and functional side-effects, some of which are:

1-Exercise Interference:

Indefinitely restricting carbohydrates to extremely low levels is particularly detrimental to endurance or strength-based athletes. While it may be effective for weight loss during off-seasons with low intensity exercises, fat fuel causes fatigue and lethargy, which interferes with the muscle building and endurance required for intense exercise during sporting seasons.


Misled by popular beliefs, most people eliminate carbohydrates and fats in their diets; regardless of whether they are trans and vegetable fats found in prepacked and fried foods, or healthy fats acquired from avocados, cheese, eggs, and oily fish, among other sources.

With the body already being overworked from switching its fuel source, reducing fat intake brings the daily calorie count to well under 1200 calories. This slows down metabolism, and the body enters a state of starvation, i.e. increased lethargy, hunger, and lack of concentration.

3-Bone Erosion:

Most essential fibers also contain carbohydrates, and cutting down on these fibers chronically deprives the body of phytic acid, oxalates and tannins; all of which are necessary for aiding optimum calcium absorption. As a result, the body becomes calcium-deficient despite adequate intake, leading to weakened bones and reduced bone growth.

Eliminating or limiting fibrous foods also promotes constipation, frequent hunger pangs, and weight gain when these natural laxatives and fullness-inducing foods are absent from a diet.

4-Easy Bruising:

The ketones produced during ketosis, and the overall change in body-wide mechanisms due to an alternate energy source also changes the blood composition by lowering platelet count (the cell that promotes clotting during injury). This makes the body more prone to bruising with the smallest of injuries.

5-Muscle Cramps:

Eliminating most fruits, starchy vegetables and legumes in a low-carb or keto diet also limits the number and amount of essential nutrients required by the body. A prolonged deficiency of vitamins and minerals like potassium, calcium, sodium, and vitamin D can result in frequent leg cramps.

6-Low Insulin:

The body produces very little insulin due to minimal carbohydrate intake. This reduced insulin production directly impacts the conversion of inactive T4 thyroid hormone into its active T3 counterpart. With less available T3, the thyroid hormone dysfunctions, resulting in hypothyroid-like symptoms, and even the actual condition in extreme cases.


The body removes excess ketones in the bloodstream as a result of ketosis by passing it out via urine. However, these large amounts of harmful ketones require more water to be flushed out, resulting in drainage of body-wide water and sodium stores, and dark-coloured urine, dizziness, exhaustion, dry mouth, dry skin, extreme thirst, and headaches.

8-Headaches and Anxiety:

Ketosis-induced dehydration isn’t the only cause of persistent headaches. Before the actual ketosis begins, the body depletes the entire carbohydrate stores and then switches to fat as fuel. This swapping process and the brain’s constant focus on using an alternative energy source are what induce the splitting headaches and concentration difficulties.

Moreover, lack of carbohydrates also means reduced serotonin and dopamine (‘feel good’ hormones) production, resulting in depression, anxiety, and reduced motivation.

9-Menstrual Disruption:

The rapid and major weight loss may improve issues with self-image and confidence. However, the body remains under constant stress the entire time by having to switch and focus on alternative fuel source. This upsets hormonal balance and disrupts the menstrual cycle in women, resulting in irregular periods, or even amenorrhea (complete lack of periods leading to infertility), in extreme cases.

While the ketogenic and low-carb diet do provide numerous health benefits, the chief being accelerated weight loss, these diets are unsustainable for the long-term and should only be followed for very short periods, like a few weeks before a major surgery.

Consult with your doctor to develop a healthier, long-term weight loss diet plan. You can also book an appointment with a top Nutritionist in Multan, Karachi and Islamabad through  for assistance to find the RIGHT Doctor for your dietary concerns.

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About the Author: Dr. Arooba

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