There are many misconceptions and myths about Ketogenic diet due to lack of explanation and unorthodox method used in this dieting system.

In this article, we will debunk popular keto myths through scientific explanations and also highlight potential concerns that might actually be true.

There are ultimately two main concerns regarding the Ketogenic diet (aka Keto diet) in terms of health risks –

  1. The first is the potential negative effects of the ‘high protein’ intake of the Ketogenic diet.
  2. Second is the effect of high levels of ketones in the body.

Please note that not all of the effects of ketosis on human physiology are known at this time.

Ketosis has been studied for almost 100 years and will most likely continue to be studied so any information provided here represents only the current base of knowledge. Find out more about the origins of Ketogenic diet here. (1, 2, 3, 4

Myth 1- Long term Keto may lead to insulin resistance

It is believed that an individual might develop insulin resistance once they are re-fed carbohydrates after long-term carbohydrate restriction under Ketogenic diet. Few individual report cases of hyperinsulinemia or hypoglycemia (low blood sugar) during the first few hours or days after going back to a carb-heavy diet. (1, 2, 3, 4, 5

This was believed to be caused by the interference of ketones with insulin binding and glucose utilization. However, further research on the topic proved that the initial cases of blood sugar swings are caused by changes in enzyme levels involved in both fat and carbohydrate burning, and not ketones. In fact, it was found that ketones actually improved insulin binding.

Further, it was found that the few cases of reported blood sugar swings were caused in individuals who had a pre-existing glucose control problems. Additionally, the level of enzymes returned to normal levels within a day of re-feeding carbohydrates.

Ketones themselves have no impact on how cells respond to insulin even though it is believed that Ketogenic diets alter fat cells, making them more likely to store fat when the diet is ended.

Practical experience shows this not to be true as many individuals have little trouble maintaining their body fat levels when the diet is stopped, especially if their activity patterns are maintained.

Landmark Study: Ketogenic Diet Impact on Insulin Levels

The first study assessing the direct impact of ketogenic diets on insulin resistance was conducted ten years ago in 2005. In it, researchers recruited 10 obese patients with type 2 diabetes and had them consume their normal diets for 1 full week. Then, the researchers provided them with a high-fat ketogenic diet for 2 weeks.

After the intervention, the 10 subjects experienced a mean energy intake decrease from 3111 kcal/day to 2164 kcal/day- representing a 30.4% decrease. This resulted in a weight-loss of 1.65 kg. More significantly, insulin sensitivity improved by approximately 75%- a dramatic increase.  Additionally, hemoglobin A1c levels decreased from 7.3% to 6.8%, mean triglyceride levels decreased by 35% and cholesterol decreased by 10%. 

Key Takeaways: A ketogenic diet may substantially increase insulin sensitivity in obese subjects with type 2 diabetes.

Recommendation: If you are trying to increase your insulin sensitivity, consider utilizing a ketogenic diet.

Myth 2- Keto leads to suppressed appetite

When individuals restrict carb intake to low levels, there is a general decrease in calorie intake (and presumably appetite) even if they consume ‘unlimited’ amount of fat and protein. This drop in appetite is looked at with high concern and is believed to be highly unhealthy by many. More importantly, this suppressed appetite is linked to the increase in ketone concentration in the body.

However, recent research indicates that ketones have no impact on the decreased appetite caused during carb restriction. Several studies have compared appetite on a very low calorie (below 800 calories/day) Ketogenic diet versus appetite on a balanced diet with the same calories.

In general, no difference was seen in appetite between the two diets. This led researchers to conclude that the level of ketones in the body has no impact on appetite. Instead they clarified that what was presumed as suppressed appetite was actually a return to baseline hunger levels.

That is, during the initial stages of a diet, there is an increase in appetite, which is followed by a decrease over time. It is this decrease which is being interpreted by dieter’s as a blunting of appetite.

Additionally, it was shown that it was the higher concentration of fat and protein, both of which tend to get digested slowly, caused the body to stay full longer and reduced appetite. Moreover, protein stimulates the release of the hormone cholecystokinin (CCK) which is also thought to help regulate appetite.

Myth 3- Keto leads to dangerous cholesterol levels

The relatively high fat intake under the Ketogenic diet immediately raises eyebrows on the effect on blood lipids and the potential increase in risk of heart diseases. It is true that under normal diet, consumption of excess fat does has a strong impact on blood lipids and increases the levels of low density lipoproteins (LDL) that is associated with heart diseases, stroke, etc.

However, there is no such evidence to establish the same about Ketogenic diet. Some initial studies did show an increase in the levels of blood lipid levels. However, many later studies confirmed that Ketogenic diet did not have any impact on cholesterol levels.

A big support in favor for Ketogenic diet comes from two particular cases. First, in the case of Inuits, who maintain a Ketogenic diet for long periods of time every year but do not develop heart disease as quickly as other Americans. And, second, in the case of epileptic children who were treated with Ketogenic diet over long periods of time. They also showed no such impact on blood cholesterol levels.

Since no absolute conclusions can be drawn regarding cholesterol levels on a Ketogenic diet, dieters are encouraged to have their blood lipid levels monitored for any negative responses.

Myth 4- Keto leads to low energy levels

Many dieters have reported that they feel light-headedness while moving from a sitting to a standing position. Sure, the body’s most efficient fuel carbohydrate has been replaced by fats, and thus the metabolism might get sluggish.

However, the belief that ketosis caused this to happen is false as studies have established that such symptoms could be easily avoided by providing sufficient supplemental minerals, primarily sodium (about 4-5 grams).

In most individuals fatigue should disappear within a few days to a few weeks at most. If fatigue remains after this time period, small amounts of carbohydrates can be added to the diet, as long as ketosis is maintained, or the diet should be abandoned for a more balanced diet.

Keto can generally sustain low-intensity aerobic exercise without problem after a period of adaptation. However because carbohydrates are an absolute requirement to sustain high intensity exercise such as weight training or high-intensity aerobic exercise, a standard Ketogenic diet is not appropriate.

Myth 5- Keto negatively impacts brain function

A well known effect of Ketogenic diets is the increased use of ketones by the brain, which also explains its success in the treatment of childhood epilepsy. However, due to the considerable change in the way brain extracts energy, many concerns have been raised for potential side effects including permanent brain impairment and short term memory loss.

What one need to understand is that ketones are absolutely normal physiological substances and were designed to provide the brain with fuel when glucose (or food in general) is not available.

The brain develops the enzymes required to use ketones during fetal development and these enzymes remain present throughout our life, which should serve to illustrate that ketones are normal fuels, and not toxic byproducts of an abnormal metabolism.

However, since there are no specific studies conducted regarding the Keto diet’s direct impact on brain impairment over long term, it is difficult to ascertain anything.

Some individuals have noted mental fatigue and a lack of concentration during the first 1-3 weeks of a Ketogenic diet. In practical terms, this means that individuals who operate heavy machinery, or need maximum mental acuity for some reason (i.e. a presentation or final exam) should refrain from starting the diet during this time period.

Myth 6- Keto increases uric acid levels

Both Ketones and uric acid compete for the same transport mechanism in the kidneys. Uric acid is a waste product of protein metabolism that is excreted through the kidneys. Under normal circumstances, uric acid is excreted as quickly as it is produced and does not allow any collection, which prevents gout.

However, due to the low carb intake combined with the increased excretion of ketones from the kidneys, uric acid levels in the bloodstream may increase.

Several studies on the Ketogenic diet have shown a consistent initial increase in uric acid levels in the blood during the initial phases of the diet. However, in most cases the levels return to normal within the first few weeks of the diet.

This build up can be easily avoided by maintaining the carb intake of 5% of total daily calories and drinking plenty of water. In any case, examples of severe disorder such as gout have been found to be rare.

To be on the safe side, individuals with a genetic predisposition towards gout should either include a minimal amount of carbohydrates (5% of total calories) in their diet or not use a Ketogenic diet.

Myth 7- Keto leads to kidney stones and kidney damage

A common concern voiced about Ketogenic diets is the potential for kidney damage or the passing of kidney stones, due to the increased workload on kidneys from having to filter ketones, urea, and ammonia.

Further, dehydration may also cause kidney stones in predisposed individuals. Finally, the ‘high-protein’ nature of Ketogenic diets alarms some individuals who are concerned with potential kidney damage.

Overall there is little data to suggest any negative effect of Ketogenic diets on kidney function or the incidence of kidney stones. In epileptic children, there is a low incidence (~5%) of small kidney stones. This may be related to the dehydrated state the children are deliberately kept in rather than the state of ketosis itself.

The few short term studies of adults suggest no alteration in kidney function (by measuring the levels of various kidney enzymes) or increased incidence of kidney stones, either while on the diet or for periods up to six months after the diet is stopped.

With regards to the protein issue, it should be noted that kidney problems resulting from a high protein intake have only been noted in individuals with preexisting kidney problems, and little human data exists to suggest that a high protein intake will cause kidney damage.

However, much of this is predicated on drinking sufficient water to maintain hydration, especially to limit the possibility of kidney stones. Individuals who are predisposed to kidney stones (or have preexisting kidney problems) should consider seriously whether a Ketogenic diet is appropriate for them. If they do choose to use a Ketogenic diet, kidney function should be monitored with regular blood work to ensure that no complications arise.

Myth 8- Keto leads to liver damage

Another concern often raised with Ketogenic diet is the potential negative effects on liver.

However, a few rare longer-term (4 weeks) studies of the Ketogenic diet, where liver enzymes were measured and no change was observed, dispel any such concern. Additionally, no liver problems are encountered in epileptic children.

Myth 9- Keto leads to severe constipation

Arguably one of the more common side-effects seen on a Ketogenic diet is that of reduced bowel movements and constipation. In all likelihood, this stems from two different causes: a lack of fiber due to lower carb intake and increased gastrointestinal absorption of foods.

To make a Ketogenic diet as healthy as possible, some type of sugar-free fiber supplement or a large salad containing fibrous vegetables may help with regularity and should fit easily with the 30 gram carbohydrate limit should be used.

One interesting effect of the Ketogenic diet is the typically reduced stool volume seen. This is however caused by the enhanced absorption/digestion of foods which leads to less waste products being generated and is not a sign of constipation.

Myth 10- Keto leads to vitamin/mineral deficiencies

The restricted food choices of a Ketogenic diet raise concerns about possible deficiencies in vitamin and mineral intake. Any diet which is restricted in calories, whether Ketogenic or not, will show a decrease in micro-nutrient intake compared to a similar diet at higher calories.

Thereby, let us stress hear again that the Ketogenic diet should not be used long term (unless indicated for medical reasons), or individuals on the Ketogenic diet should use their small carb allowance to maximize vegetable intake.

To avoid deficiencies, a basic multi- vitamin/mineral (providing at least the RDA for all nutrients) may be taken daily. If intake of dairy foods, such as cheese, is also low then a calcium supplement may be warranted.

Myth 11- Keto leads to electrolyte excretion

The diuretic (dehydrating) nature of ketosis causes an excretion of three of the body’s primary electrolytes: sodium, potassium, and magnesium. These three minerals are involved in many processes in the body, one of which is the regulation of muscle contraction, including the heart.

A severe loss of electrolytes is problematic. At the least, it can cause muscle cramping, which is often reported by individuals on a Ketogenic diet. At the extreme, it can compromise normal heart function and could cause fatal heart arrhythmias.

To prevent any serious condition, suggested amounts for the three primary electrolytes may be included in the diet:

  • Sodium: 3-5 grams in addition to the sodium which occurs in food
  • Potassium: 1 gram in addition to the 1-1.5 grams of potassium which occur in food
  • Magnesium: 300 mg

Caution: An excessive intake of any single mineral (especially potassium) can be just as dangerous as a deficiency. At no time should mineral supplements be taken in excess.

Myth 12- Keto leads to calcium loss/Osteoporosis

There is some evidence that the Ketogenic diet causes disordered calcium metabolism, especially if it is combined with drug treatment for epilepsy. However, the effect can be easily reversed if adequate Vitamin D is consumed.

Additionally, depending on dairy intake, a calcium supplement may be necessary to ensure positive calcium balance (1200 milligrams/day for men and pre-menopausal women and 1500 mg/day for post-menopausal women).

Myth 13- Keto leads to weight/fat regain once stopped

It has been found that typically less than 5-10% of individuals who lose weight through any form of dieting alone are able to maintain that weight loss in the long term.

The concern of weight regain is especially greater for Ketogenic diets compared with other diets, as most people confuse loss of body weight with loss of body fat.

The dehydration and glycogen depletion which occurs on Ketogenic diets can be anywhere from 1 to 15 pounds of body weight. Thus it is to be expected that this weight will be regained when carbohydrates are reintroduced into the diet.

For individuals who fixate on the scale as the only measure of their progress, this weight regain can be disheartening and may make the individual fear carbohydrates as the source of their excess body weight.

Dieters must realize that the initial weight gain is water and glycogen (carbohydrate stored in the muscle) and move past it. Focusing on changes in body composition should avoid psychological problems with the weight regain from replenishing water and glycogen.

Myth 14- Keto leads to Optic Neuropathy

One unusual side effect of Ketogenic diets which has appeared in a few cases is the development of optic neuropathy, which is a dysfunction of the optic nerve.

In all cases, the problem was linked to the fact that the individuals in question were not receiving calcium or vitamin supplements for periods of up to a year. Supplementation of adequate B-vitamins, especially thiamine, corrected all cases which were reported. Ketogenic diet, per se, was found not responsible for any such condition.

Myth 15- Keto leads to hair loss and decline in nail quality

A final effect which has occasionally been noted, primarily during total fasting, is transient hair loss. In a related vein, some individuals have reported changes in the quality of their finger and toe nails primarily due to vitamin and mineral deficiency.

This could be easily avoided by including lots of green vegetables in the 30 gram carb quota daily. No link of ketosis, the increase in the concentration of ketone bodies, and ketogenic diet has been found with hair loss and decline in nail quality.

Myths about Ketogenic Diet