Negative Aspects of a ketogenic Diet

Is a Keto diet bad for you?

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Like all diets, it has its downsides

A Ketogenic Diet, which is a very low carbohydrate, moderate protein and high fat diet very effective in producing a rapid weight loss and in reducing total body fat, Body Mass Index and improving key indicators, by reducing values of total cholesterol, LDL cholesterol, triglycerides and sugar and increasing HDL cholesterol values.

However, some negative side effects have been observed in studies involving rodents which raise concern about a keto diet's adverse effects.

This article reviews the scientific evidence that supports or disproves these studies on the health risks of a keto diet, and it also looks into the high risks of obesity.

Short-Term Side Effects

Which are the risks of a keto diet?.

Masood and Uppaluri (2018) ( 1 ) looked into the side-effects of a keto diet and mentioned a group of symptoms that are usually knare known collectively as "keto-flu" because they resemble those of influenza:

Keto Flu

  • Nausea
  • Vomiting
  • Dizziness
  • Headache
  • Fatigue
  • Insomnia
  • Constipation
  • Low tolerance to exercise and training

These adverse effects occur on short diets and usually clear up after a few days, but sometimes can also last a few weeks. They respond well to an adequate fluid intake and a correct electrolyte balance ( Visit our Do I need eight glasses of water a day? webpage for more information on keeping hydrated).

These take place as the body adapts to a lower level of glucose and turns to ketone bodies as a primary energy source.


The shift in diet which elminates most carbohydrates may also lead to a drop in the amount of fiber consumed (Some "high" carb foods such as potatoes, onions and oatmeal for instance are quite rich in fiber: these three have roughly 2% fiber -2 g per 100 g serving, and eliminating them from your diet reduces your fiber bulk).

This plus the increased loss of fluids and some key electrolites such as magnesium during the first days of ketosis may cause constipation.

This can be avoided by eating more green, leafy vegetables (Kale, spinach, arugula which by the way are magnesium-rich too), drinking more water (Read more about Drinking water and Constipation).

Long-term Side Effects

A regular ketogenic diet is short, not more than 24 weeks, but longer diets many involve health risks, as is the case of children treated with a keto diet to control seizures and neurological disorders.

The keto diet was created by Russel Wilder to treat pediatric epilepsy in 1921 and it was Wilder who coined the term "ketogenic diet". There are studies that tracked the health effects of long term keto dieting in children (not in adults), and their findings are:

  • Hyperlipidemia (High cholesterol)
  • Hepatic steatosis (fatty liver)
  • Increase in Kidney stones
  • Osteoporosis
  • Impaired growth
  • Hypoproteinemia (low levels of protein in blood)
  • Vitamin and mineral deficiencies

Nevertheless the risks do not appear to be deadly because a study by Kosinski and Jornayvaz, (2017) ( 2 ), found that subjects following a low-carb, high-protein diet were not affected "with higher mortality after 12 years of follow-up".

We will look into each of these adverse effects below:

Does a keto diet increase Cholesterol and Triglycerides?

The high quantity of fat required by a Keto Diet can cause some concern regarding the potential increase of blood lipids (cholesterol and triglycerides).

But the effect is actually the opposite: Paoli (2014) ( 3 ) found that most studies show that a keto diet reduces total cholesterol and increases the "good" HDL-cholesterol. It also reduces triglycerides.

Regarding the "bad" LDL-cholesterol, the diet "increase[s] the size and volume of LDL-C particles which is considered to reduce cardiovascular disease risk since smaller LDL particles have a higher atherogenicity." This means that unlike smaller LDL particles, the larger ones don't provoke the buildup of deposits on arterial walls.

Apparently the lower blood glucose levels caused by a low carb keto diet means lower insulin levels which in turn reduce the activation of an enzyme that synthesizes cholesterol (the enzyme is called HMGCoA), si less cholesterol is produced.

Take home point

Very low risk of high cholesterol or triglycerides due to a keto diet.

However, a long-term 22 weeks diet in mice produced high levels of blood lipids, an outcome which is completely different to the one found in human subjects. There are several studies that have a different outcome in rodents when compared to humans as you will see as we review each risk and its effects in mice or rats.

Keto diet: On mice and men

The Ketogenic diet used in rodents is quite different to the one used in humans, and the fat composition, and fat-to-protein ratios are also different, which may lead to differences in the outcome of these studies.

These different reactions may be due to species-differences in metabolism (2) and also the duration of the studies (22 weeks in the lifespan of a mouse is equivalent to several years in a human being).

How long is it safe to be in ketosis?

Dashti (2004) ( 4 ) Studied 83 obese subjects with a BMI greater than 35, they dieted for 24-weeks with a ketogenic diet with the following macros: 30 g carbohydrate, 1 g/kg body weight protein and the fats were distributed as follows: 20% saturated fat, and 80% polyunsaturated and monounsaturated fat.

All lost weight and BMI, and also improved all key indicators: total cholesterol (drop), HDL (increased), LDL (decrease), Triglycerides (drop), sugar (drop).

The conclusion: "the present study confirms that it is safe to use a ketogenic diet for a longer period of time than previously demonstrated".

Ketogenic diet and cardiovascular disease

We have not found studies indicating any negative side-effects regarding heart disease, such as heart palpitations. Actually the effects reported are positive ones (For more details, visit our Keto Diet Review page).

Fatty Liver

The same long term (22 week) study found that mice developed hepatic steatosis (fatty liver).(2).

Kosinski and Jornayvaz (2017) (2) review of three meta-analyses (studies that group other studies to find correlations that link different variables) found a similar effect: either liver inflammation or fatty liver (Non-alcoholilc Fatty Liver Disease or NAFLD).

These findings have not been reported in studies involving human subjects. So the case is open whether a Keto Diet can induce or on the contrary, improve NAFLD in humans (-----5).

A treatment for NAFLD in humans?

Haghighatdoost (2016) ( 5 ) found that low carb diets improved (lowered) liver fat content in subjects with NAFLD.

Take home point

Liver effects: negative in rodents, but not reported in humans.

Protein intake and the Kidneys

Kidney Stones

One of the negative effects on the kidneys is due to an excessive intake of protein. But this shouldn't be the case with a Keto Diet:

Because, as Paoli (2014) (3) points out "a ketogenic diet is not, strictly speaking, a Low carb ⁄ High Protein; Keto Diet is mainly a very low carbohydrate diet with a normal amount of protein",

Yet even though the ketogenic diet is a very low carb, moderate protein and high fat diet, those who follow it may tend to ingest more protein than recommended or increase ingestion to levels higher they are used to.

This excess protein may be avoided by following the values set down in your ketogenic diet macros for protein.

The problem is that the extra protein will be broken down into their amino acid building blocks which in turn can be converted into glucose. Extra glucose will lower ketones, increase insulin levels and interfere with ketosis.

The additional proteins when broken down produce nitrogen in a toxic form: ammonia. The liver converts ammonia into urea, which is almost non-toxic and soluble in water. Urea is excreted by the kidneys in the urine.

Uric acid on the other hand is the result of breakdown of nucleic acids and pruines, the latter are very common in different kinds of foods: animal based protein, red meat, organ meats and shellfish, it is excreted in urine.

However high production of uric acid may generate an acid load which acidifies the urine and makes it easier for uric acid stones to form.

Approximately 1 in every 20 children on an epileptic keto diet suffer from kidney stones, and they are treated with potassium citrate to prevent them. ( 6 )

Take home point

Avoid kidney stones by following your protein macro values.

Kidney Issues

Risk of kidney pain during ketosis: some subjects (patients with renal insufficiency, metabolic syndrome or obesity related health conditions) may be more susceptible to high blood pressure effects caused by the amino acids resulting from the proteic component of a keto diet.

As a positive note, Paoli (2014) (3) also mentions that a "very low carb keto diet" reverted the damage of diabetic kidney damage in mice.

Take home point

If you have renal issues, don't follow a ketogenic diet.

Osteoporosis and stunted growth

Some studies with rats, (3) reported that a keto diet causes a reduction in a hormone known as IGF-I or IGF-1 (insulin like growth factor 1). As its name hints, it is a protein very similar in its structure to insulin. It promotes growth in children and correct body functions in adults. So it may have an impact on children under long-term ketogenic diets.

The rat studies also show that bone mass density is impaired during a Keto Diet. These studies lasted 4 weeks (a very long period of time in comparison to their lifespan).

But "recently published articles suggested that there is not a negative effect on bone health" (3).

Take home point

Studies in rats show osteoporosis and weaker bones.

Vitamin deficiencies

Vitamin deficiencies in long-term keto diets (such as those used in eplieptic children) may arise from the lack of fresh fruits and vegetables in their very low carb diet.

Supplementation should cover any vitamin or mineral needs.

Take home point

Take your regular multivitamin supplement while dieting.

Glucose intolerance and Insulin Resistance

The review by Kosinski and Jornayvaz (2017) (2) found that a ketogenic diet produces insulin resistance and glucose intolerance in rodents.

This finding is supported by a recent study (Grandl, 2018) ( 7 ), which involved mice. It found that there may be an increased risk of insulin resistance caused by a keto diet which could lead to Type 2 diabetes.

The authors plan to follow up on this study to find out if the products that result from metabolization of fatty acids either in a keto diet or in a typical high-fat Western diet, somehow interact with the signals of the brain to provoke this resistance.

But, once again, the keto diet in humans it produces a better control of sugar levels leading to a reduction in the use of antidiabetic medications in subjects with type-2 diabetes (2).

To avoid sensitization and any negative effect on glucose metabolism, Paoli (2014) (3) suggests implementing a transition phase to move out of a ketogenic diet and into to a normal diet.

Take home point

Keto Diet may increase the risk of type 2 diabetes in rats

Diabetes: very important advic

Masood and Uppaluri (2018) (1) recommend that subjects suffering from diabetes and use insulin or other hypoglycemic medications can suffer episodes of hypoglycemia (low blood sugar) unless they adjust their medication dosage before starting this diet.

Cautions and Counterindications

Masood and Uppaluri (2018) (1) also list a series of conditions which may interact with a ketogenic diet:

Don't follow a ketogenic diet if you suffer from liver failure, pancreatities, porphyrias or disorders of fat metabolism.

General Diet Recommendations

Most people who lose weight are likely to find it difficult to keep the weight off. They can improve their chances by adopting a lifelong commitment that includes:

  • Increased frequent and regular physical activity of at least moderate intensity, and
  • Healthy eating in accordance with the Dietary Guidelines for Americans, emphasizing a reduction in total calories, a lowered fat consumption, and an increase in vegetables, fruits and whole grains

Even a modest weight losss (5 - 10 percent of body weight, 10 - 20 pounds) will improve your health and lower health risks associated to being overweight.

Unless medically indicated, weight loss after the first two or three weeks of dieting should not exceed a rate of three pounds or approximately one and one-half percent of body weight per week.

More rapid weight loss may cause an increased risk of developing gallbladder disease, risk which is believed to be higher than the risk of developing gallbladder disease as a result of staying overweight ⁄ obese.

People who are considered medically appropriate for more rapid weight loss should have their progress monitored by a physician.

Very-low-calorie diets (less than 800 kcal per day) are designed to promote rapid weight loss in people whose obesity has resulted in, or has put them at medical risk of, developing serious health complications. Rapid weight loss may also be associated with some medical problems. A weight loss program should include medical supervision to minimize risks associated with rapid weight loss.

People undergoing weight loss can experience physical changes in the body (dizziness, interruptions in the menstrual cycle, hair loss, for example) that may indicate more serious conditions. People noticing such changes should be advised to talk immediately to their primary care physician.

Children and adolescents, pregnant or breast feeding women, and people with significant health problems such as bulimia, heart disease, kidney disease, diabetes or psychiatric disorder, should not begin this program without written authorization by their primary care provider.

People under treatment for other conditions or taking medications prescribed by their health care provider should tell their providers that they have begun this diet because, in some cases, adjustments to medications or modifications to the weight loss program may be appropriate.

The Risks of Being Fat

We have seen that there are several potentially negative side-effects, some of them have been studied in mice with conflicting outcomes to studies performed on humans.

It is important to know and assess these health risks before embarking on a ketogenic diet (or any other diet). It is also important to discuss the matter with your physician.

However being obese involves a series of risks such as type 2 diabetes, metabolic syndrome, insulin resistance, glucose intolerance, high blood sugar levels, chronic low-level inflammation which is associated to increased risks of osteoporosis.

Visceral or abdominal fat is associated with cardiovascular disease, high blood pressure, dementia, asthma, cancer (colorectal and breast cancers) and type 2 diabetes risk.

Take home point

Obesity increases the risk of heart disease, diabetes and cancer.

We discuss these risks in our "The Dangers of Belly Fat" webpage:

Read More:

> > The Dangers of Belly Fat

So, the "cons" of a keto diet should also be weighed against the "cons" of obesity, because many of the negative aspects of a ketogenic diet have not yet been definitively proved for humans, but those of obesity are real and life-threatening.

If you are interested, we discuss the Keto Diet and its benefits in detail in our "Ketogenic diet" webpage:

Read More, visit our:

> > Keto Diet Review

two overweight women view of rear and thick waist
Obesity, full hips and wide waist

Cite this article:

. ©2018. Negatives of a Ketogenic Diet. Patagonia Wellness, 11 Oct. 2018.

Tags: Risks of a keto diet, negative aspects keto diet, ketogenic diet, keto diet,Obesity

Subject: Negative aspects of a Ketogenic diet. The health risks involved in a keto diet. Is it bad for you?


References and Further Reading

(1) Wajeed Masood; Kalyan R. Uppaluri, (2018). Ketogenic Diet, 2018, StatPearls Publishing LLC. Bookshelf ID: NBK499830PMID: 29763005

(2) C. Kosinski and F. R. Jornayvaz, (2017). Effects of Ketogenic Diets on Cardiovascular Risk Factors: Evidence from Animal and Human Studies, Nutrients. 2017 May; 9(5): 517. 2017 May 19. doi: 10.3390/nu9050517

(3) Antonio Paoli, (2014). Ketogenic Diet for Obesity: Friend or Foe?, Int J Environ Res Public Health. 2014 Feb; 11(2): 2092-2107. 2014 Feb 19. doi: 10.3390/ijerph110202092

(4) Hussein M Dashti, et al., (2004). Long-term effects of a ketogenic diet in obese patients, Exp Clin Cardiol. 2004 Fall; 9(3): 200-205

(5) Fahimeh Haghighatdoost, Amin Salehi-Abargouei, Pamela J. Surkan, and Leila Azadbakh, (2016). The effects of low carbohydrate diets on liver function tests in nonalcoholic fatty liver disease: A systematic review and meta-analysis of clinical trials, J Res Med Sci. 2016; 21: 53. 2016 Jul 29. doi: 10.4103/1735-1995.187269

(6) Sampath A, Kossoff EH, Furth SL, Pyzik PL, Vining EP, (2007). Kidney stones and the ketogenic diet: risk factors and prevention, J Child Neurol. 2007 Apr;22(4):375-8

(7) G. Grandl, et al., (2018). Short term feeding of Ketogenic Diet induces more severe Hepatic Insulin Resistance than obesogenic High Fat Diet, Journal of Physiology (2018). DOI: 10.1113/JP275173