Does the Ketogenic Diet Really Work So Well? All Investigations in a Row

The keto madness seems to be starting. According to Google trends, there is a strong upward trend on the subject of ‘ketogenic’.

This article contains all reliable studies about the keto diet that you can use as a substantiation. I have already written an article about the keto diet  , but this article focuses more on the scientific basis for this new hype.

In this article I make almost no use of in vitro studies or animal studies in view of the low reliability, but mainly of RCTs, meta-analyzes and systematic reviews. These come primarily from Pubmed and the Cochrane Library .

What is the keto diet: a short introduction

Despite the recent hype, a keto diet is not something new. It has been used for nearly 100 years to treat drug-resistant epilepsy, especially in children ( source ).

But what exactly is the keto diet? To be able to follow a keto diet you must be capable of ketosis . An extremely low carbohydrate force forces the body to enter a ketosis state.

Ketosis occurs when people follow a fanatically low-carbohydrate diet and the concentration of ketones in the blood rises.

This simply means that your body burns fatty acids (ketones) for energy instead of carbohydrates (glycogen in the liver and glucose in the blood). While we are in ketosis, the concentration of ketones in the blood increases.

To bring your body into the state of ketosis, you should drastically limit carbohydrate consumption to a maximum of about 50 grams ( source ,  source ). Most people will come in ketose with up to 50 grams of carbohydrates per day, while some have to limit their carbohydrate intake to less than 30 grams per day.

Ketones are a by-product of the breakdown of fats. Measuring ketones can therefore give an indication of whether the body is in a ketogenic state.

The only way to know for sure if you are capable of ketosis is to determine the concentration of ketones in our body.

You can do this in different ways:

  • Measure ketones in the urine
  • Measure ketones in the blood
  • Measure ketones via the breath

In this article you will learn how you can measure the ketone levels in your body with the help of ketose sticks and ketose strips. I also explain which method produces the most accurate results.

Does the keto diet work if you want to lose weight?

In a randomized controlled trial (RCT study) from 2003, the effects of a strict low-carbohydrate diet were compared with those of a low-fat diet on weight loss ( source ).

The study group of 16 participants was instructed to consume less than 20 grams of carbohydrates per day for 2 weeks, then this group was put on a low-carbohydrate diet of less than 40 grams of carbohydrates per day for a period of 10 weeks. The control group (which consisted of 14 participants) was instructed to consume less than 30% of their daily calorie requirement from fat.

The results of this study indicate that the low-carbohydrate group lost more weight than the low-fat group (on average, 9.9 ± 9.3 kg versus 4.1 ± 4.9 kg).

In another randomized controlled trial from 2003, 132 obese participants were randomly assigned to a strict low-carbohydrate diet or a low-fat / calorie diet for a period of 6 months ( source ).

The participants who were assigned to the low-carbohydrate diet were instructed to limit carbohydrate intake to 30 grams of carbohydrates per day or less. The total fat intake did not have to be limited. The group assigned to the low-fat diet had to extract less than 30% of the daily calorie intake from fat. The low-fat group also had to create a deficit of 500 calories per day through calorie restriction.

This study shows that the obese participants lost more weight on a fanatic carbohydrate-restricted diet than on a low-fat diet (on average -5.8 ± 8.6 kg vs. -1.9 ± 4.2 kg).

A recent randomized controlled trial with parallel groups from 2014 compared the cardiovascular effects of a strict low-carbohydrate diet with those of a low-fat diet for 12 months ( source ).

The 148 male and female participants were put on a strict low-carb diet (40 grams or less per day) or a low-fat diet (30% or less of the daily energy intake consisted of fat). Data on cardiovascular risk factors, body weight and nutritional composition were collected at 0.3, 6 and 12 months.

After 12 months, a greater weight loss was found in the low-carb group (mean difference between the groups was 3.5 kg) than in the low-fat group. The HDL cholesterol (the ‘good’ cholesterol) also appeared to have been raised considerably after 12 months in the low-carb group.

Below are even more research results from randomly selected systematic reviews and randomized controlled trials that compared low-fat diets and ketogenic diets.

All mentioned studies vary from 6 months to 12 months:

StudyKeto diet weight lossLow-fat diet weight loss
PA Dyson et al. 2007– 6.9 kg– 2.1 kg
Tian Hu et al. 2012– 6.1 kg– 5 kg
FR Samaha et al. 2003– 5.8 kg– 1.2 kg
Bonnie J Brehm et al. 2003– 8.5 kg– 3.9 kg
Sackner-Bernstein et al. 2015– 7.8 kg– 5.9 kg
WS Yancy et al. 2004– 9.4 kg– 4.8 kg

As we can see from the above data, there is weight loss in both types of diets. It immediately becomes clear that very fanatic low-carb (keto) diets lead to the loss of considerably more weight than low-fat diets.

The average weight loss between the aforementioned studies is 3 kg extra for keto diets. Is this a clinically significant amount of weight reduction for people who are obese or extremely overweight? Maybe for someone with a body weight of 120 kg. But in my opinion this is still considerable. Because you can also view it from the other side. Every kilo that you lose extra has a motivating effect and brings you closer to your goals.

Does the keto diet work for fat burning?

A randomized controlled study from 2004 investigated the effects of a keto diet and a low-fat diet on weight loss and body composition in overweight men and women. A total of 15 healthy (but overweight) men and 13 premenopausal women participated in the study ( source ).

The participants were divided between the keto group and the low-fat group. In the keto group, carbohydrate intake was reduced to below 10% of the daily calorie intake in order to make the test subjects capable of ketosis. The amount of calories was reduced in both groups to create a calorie deficit, but for the men the keto diet was slightly higher (1855 calories per day) than the low-fat diet (1562 calories per day).

Despite the considerably higher calorie intake, the male participants on the keto diet were found to have lost more body fat than the male participants in the low-fat group. The majority of women also responded favorably to the keto diet, especially with regard to fat loss around the abdominal area (visceral fat).

The substantial decrease in abdominal fat was not only due to the total fat loss, because the ratio between abdominal fat and the total amount of fat was also significantly reduced in men and women on the keto diet.

Does the keto diet work with epilepsy?

In a literature review of published data between the 1920s and 2003 regarding the efficacy of the keto diet, it appears that the keto diet appears to be a particularly effective treatment for epilepsy ( source ).

This is especially true for children with a difficult-to-treat form of  epilepsy  that cannot be sufficiently controlled with regular medication ( source ).

A large meta-analysis (cluster of studies) was carried out in 1998 to evaluate the effectiveness of a fanatic low-carbohydrate diet in children with epilepsy. Nineteen different studies with 1084 young patients were analyzed and assessed. The main findings are that 16% of the young patients were declared seizure-free, while 32% of the children noticed an attack reduction of 90% or more. For 56% of the patients, epileptic seizures decreased by half or more ( source ).

In another 2001 study, 150 children with epileptic seizures that were difficult to control were put on a 12-month keto diet. Three to six years after the start of the keto diet, all 150 families were sent a questionnaire with questions about the current health status of their child and the frequency of epileptic seizures. Of the 150 families, 107 families completed the questionnaire.

The questionnaire shows that:

  • 13% of the children were declared attack-free
  • 14% had a 90% to 99% reduction in their attack frequencies
  • 29 children were free from medication
  • 28 children were put to 1 medication
  • 15 children continued to follow the keto diet

The research results from the above studies support the use of the keto diet in children with epileptic seizures that are difficult to control. It may cause some patients to take less or no anti-epileptic medication (medication) at all, while still being free of seizures. It is still unclear how the keto diet reduces epileptic seizures.

Does the keto diet work with diabetes?

Diabetics on a keto diet often notice a significant reduction in blood sugar levels. This applies to both type 1 diabetes and type 2 diabetes.

Several studies have shown that a keto diet helps to control blood sugar levels and also brings other beneficial health effects ( source , source , source ).

In a 16-week study, 17 out of 21 diabetics were able to remedy their condition by following a keto diet. This means that diabetics no longer need insulin or medication. The participants lost an average of 8.7 kg and also saw their waist size decrease and their triglyceride values ​​and blood pressure normalize ( source).

In a recent 2018 study, 94% of patients were able to stop injecting insulin because they had followed a keto diet. They also lost 12% of their starting weight in the same year ( source ).

In addition, the Keer Diabetes 2 Om program, after 12 months, helped 87% of participants with diabetes wholly or partially stop or reduce their medication use ( source).

Does the keto diet work with neurological disorders?

A prospective cohort study from 2005 investigated the relationship between unsaturated fatty acids and the risk of Parkinson’s disease. The goal of the researchers was to determine whether a high intake of unsaturated fatty acids can be associated with a reduced risk of Parkinson’s disease.

The study, involving 5395 participants of at least 55 years of age, shows that a higher consumption of saturated fat reduces the risk of dementia by 9% ( source).

A 2012 study in which 937 elderly people were followed for a period of 3.7 years showed that ( source ):

  • Older people who ate the highest proportion of carbohydrates at 89% increased risk of mild cognitive impairment or dementia
  • Elderly people who ate the most protein in proportion had a 21% reduced risk of mild cognitive impairment or dementia.
  • Older people who ate relatively the most fats had a 44% reduced risk of mild cognitive impairment or dementia.

The research results show that a low-carbohydrate diet lowers the risk of cognitive impairment.

Does the keto diet work with cancer?

No diet can cure cancer, but some studies have shown a link between the keto diet and the delayed growth of some types of tumor in mice ( source ).

When you reduce the amount of glucose in the diet (such as ketogenic diets), you interrupt the growth of tumor cells according to some study results ( source , source ). Cancer cells are fueled by increased glucose uptake (the so  called Warburg effect , where energy only takes place through glycolysis) ( source ).

Cancer cells are unable to switch to ketones as fuel because they can only survive on glucose. In the absence of this metabolic flexibility, cancer cells go hungry. Despite the promising evidence in animals, the keto diet in cancer patients has not been properly investigated and the results of mouse studies cannot be translated into humans one-on-one.

One of the few documented case studies was conducted on a 65-year-old woman with a brain tumor. After the operation, the patient followed a keto diet. The diet was supplemented with vitamins and minerals. After two months of treatment, the body weight of the patient was reduced by approximately 20% and no detectable brain tumor tissue was detected. Tumor recurrence (tumor regrowth) was found 10 weeks after suspension of keto diet therapy ( source ).

A quality of life study investigated the effect of a keto diet on 16 patients with advanced cancer. Several patients discontinued the study due to personal reasons or because they could not tolerate the diet. Two patients died during the study period. Of the 16 cancer patients, 5 completed the three-month intervention period.

These patients reported improved emotional functioning and reduced insomnia. With the exception of temporary constipation and fatigue, the researchers found no serious adverse side effects, especially no changes in cholesterol or blood lipids ( source ).

In another 1991 study, patients with gastrointestinal stromal tumors (gastrointestinal cancer) were examined. The researchers looked at the effect of a carbohydrate-rich diet or a keto diet on tumor growth. Tumor growth increased by more than 32% in patients following the carbohydrate-rich diet. In the patient group that followed the keto diet, tumor growth decreased by 24%. However, the difference between the two groups was not statistically significant ( source ).

Does the keto diet contribute to improved insulin sensitivity?

In a randomized controlled trial, 132 obese men and women were placed on a strict low-carbohydrate diet (keto) or a low-fat diet ( source ). Of the 132 participants, 79 subjects completed the 6-month study.

The results showed that participants on the low-carbohydrate diet lost more weight than on the low-fat diet. The low-carbohydrate group also had on average large reductions in triglyceride levels (a type of fat in the blood). Insulin sensitivity, only measured in participants without diabetes, also improved more subjects on the strict low-carbohydrate diet.

The aforementioned RCT study from 2004, in which 31 male and female participants with overweight and obesity were involved, shows that a fanatically low-carb diet leads to a significant reduction in insulin levels ( source ).

Another randomized controlled trial from 2007 shows similar results ( source ). A total of 88 obese adults were randomly assigned to either a keto diet or a low-fat / carbohydrate-rich diet. The study looked at the effect of these diets on weight loss and cardiovascular disease.

The weight loss was comparable in both diet groups (-11.9 ± 6.3 kg keto diet versus -10.1 ± 5.7 kg low-fat / carbohydrate-rich diet). Blood pressure, fasting glucose and insulin decreased at the same time as weight loss. The blood lipid profile also improved in the keto group.

In a 2006 RCT study, 83 participants were randomly assigned to a keto diet or two different carbohydrate-rich / low-fat diets ( source ). The aim was to compare the effects of the different diets on body composition and cardiovascular risk. Similar fat loss was observed among all three diets. A striking finding was that the fasting insulin level decreased by 33% under the keto diet.

Then a study was conducted among 32 healthy, obese adults to compare the effect of a keto diet (<20 grams of carbohydrates per day) with a carbohydrate-rich diet (55% carbohydrates of total energy intake) during fasting. A similar amount of weight was lost in both groups. The fasting insulin level was also found to have decreased by both diets ( source ).

Does the keto diet contribute to improved blood pressure?

Several randomized controlled trials show that fanatic low carbohydrate and keto diets can help improve blood pressure.

A 2004 randomized controlled study confirms that a fanatic low-carbohydrate diet is effective in lowering both systolic blood pressure (-10 mm Hg) and diastolic blood pressure (-5 mm Hg) ( source ).

The 31 male and female overweight and obese participants were divided between two groups: the low-carbohydrate group and the low-fat group. All participants were between 24 and 61 years old and completed the 10-week study. These data suggest that energy limitation due to strict low-carb and low-fat diets are effective in improving blood pressure in overweight and obese adults.

A randomized controlled trial from 2005 wanted to investigate the effects of a low-carbohydrate diet with a low-fat diet on 102 diabetes patients ( source ). The program lasted 3 months. The low carbohydrate group were put on a diet of up to 70 grams of carbohydrates per day. The low-fat group received standard dietary advice, with the emphasis on reducing fat intake. This restriction of fats was combined with reducing the portion sizes. Weight loss was greater in the low carbohydrate group (-3.55 +/- 0.63, average +/- sem) versus -0.92 +/- 0.40 kg, P = 0.001).

A randomized controlled 12-month study from 2007 investigated the effects of strict low-carbohydrate diets on weight loss and metabolic changes in premenopausal women ( source ). The results showed improved fasting insulin and glucose levels and blood pressure in the female participants.

Does the keto diet contribute to an improved cholesterol ratio?

A 2013 meta-analysis, published in the British Journal of Nutrition, looked at the effects of keto diets on cardiovascular health including HDL cholesterol ( source ). The meta-analysis consisted of 13 randomized controlled trials with a total of 1415 diabetics. All studies provided less than 50 grams of carbohydrates per day to the participants. That is lower than the daily recommended amount that is normally recommended for diabetes patients.

All examinations took place for at least 12 months, and all participants were older than 18 years. In each of these studies, keto diets were compared with low-fat diets. All 12 studies investigated the effect of a keto diet on HDL cholesterol levels. It turned out that the participants had an average increase in HDL cholesterol of 0.12 mmol / L. This increase was twice as much as with low-fat diets (0.06 mmol / L). The researchers conclude that keto diets can improve cardiovascular health because they increase HDL cholesterol levels in the body.

Do you want to know if a keto diet improves your cholesterol levels? Then check your cholesterol ratio. Researchers suggest that this is a good predictor for the risk of cardiovascular disease. The cholesterol ratio is the ratio between total cholesterol and HDL cholesterol. The ratio between total cholesterol and HDL cholesterol should be less than 5.

In addition, HDL cholesterol can have anti-inflammatory effects. A 2014 study shows that HDL cholesterol may be responsible for reducing inflammatory activities. This is done by regulating the cells of the immune system that are also called macrophages ( source ).

Does the keto diet work with GLUT1 deficiency syndrome?

The GLUT1 deficiency syndrome is a rare genetic condition in which insufficient glucose enters the brain. Glucose is an important energy source for the brain.

Some symptoms arise immediately after birth and include developmental delay, motor problems and seizures.

Unlike glucose, the use of ketones as a fuel does not require this protein to pass from the blood to the brain. That is why the keto diet can offer an alternative energy source for children with this condition.

The keto diet appears to improve various symptoms of the condition. Several studies report a reduced frequency of seizures and an improvement in muscle coordination, alertness and concentration in children on the keto diet ( source , source , source ).

Does the keto diet work with non-alcoholic fatty liver?

Non-alcoholic fatty liver (NAFLD) is the most common liver disease in the western world and affects around 25% of the world’s population ( source ).

It is often accompanied by type 2 diabetes, metabolic syndrome and obesity. There are indications that non-alcoholic liver fat improves when following a keto diet ( source , source , source ).

In a small study (pilot study), 14 obese male participants with metabolic syndrome and NAFLD had followed a keto diet for 12 weeks ( source ). The researchers saw a significant decrease in body weight and liver enzymes and an improvement in blood pressure. Even more impressive was that 93% of the men had a liver fat reduction and that liver fat had disappeared in 21% of the participants.

What are the dangers of the keto diet?

The following hazards emerge from various studies:


The keto diet can cause various side effects and constipation is a common side effect. A 2015 study in which 48 children with persistent epilepsy followed a keto diet shows that 65% of patients suffered from constipation ( source ).

Kidney stones

Kidney stones have been associated with the keto diet. A 2007 cohort study investigated the possible link between a keto diet and the risk of kidney stones. Of the 195 children with persistent epilepsy, 13 developed kidney stones. Oral administration of potassium citrate significantly reduced the prevalence of kidney stones ( source ).

Bad breath

Studies show that a breath odor of acetone is a common side effect in people who get into ketosis.

Research results show that the levels of acetone in the breath are directly related to an increase in blood sugar and acetoacetate in the blood ( source , source ). This creates a fruity odor that is caused by an increased concentration of ketones. The specific culprit is acetone, a type of ketone that leaves the body through urine and breath ( source ).

Decreased training performance

People who practice anaerobic sports with a high intensity and short duration (such as sprinters), see their performance deteriorate when they are on a keto diet, according to recent research ( source ).

Researchers at Saint Louis University tested the anaerobic training performance of 16 men and women after a four-day keto diet or a carbohydrate-rich diet.

The participants who followed the keto diet performed less well with anaerobic exercises than people who ate more carbohydrates. Depending on the exercise, their performance was 4% to 15% lower than that of the carbohydrate group.

Although this was a small-scale study from 2018 and people were only busy with different diets for a few days, an earlier study from 2017 showed similar results during short-term physical activities ( source ).


The keto diet is not a marketing trick or a passing trend. The state of ketosis not only contributes to weight reduction in the short term, the keto diet also has beneficial health effects on the body in the long term. It is a diet that is supported by science and the evidence is in the aforementioned studies.

A ketogenic diet can be an interesting alternative to treat certain conditions and can speed up weight loss. But it’s not easy to follow. We also don’t know much about the long-term effects, probably because it is difficult for most people to sustain in the long term.

I think the keto diet is a bit extreme but I don’t see any dangers in eating a lot of avocado, oils, etc. It seems a bit like the paleo diet and the low carbohydrate diet because you mainly remove the processed carbohydrates.


Fan of everything health and fitness related. My mission is to share my knowledge and experience with as many people as possible and help them to find their ideal path to perfect health.