Even though four decades, the ketogenic diet is still causing controversy regarding its benefits and safety. The ketogenic diet was first recognized in the 1920s as a diet for epilepsy treatment. Research on the ketogenic diet has found various other benefits, both those that have been proven and those that still require further research, including diabetes mellitus and cardiovascular disease.

Effects of Ketogenic Diet

The ketogenic diet is a diet low in carbohydrates and high in fat. Based on the different macronutrient proportions, the ketogenic diet is divided into three, namely:

1. The classic ketogenic diet (by the American Diabetes Association)
  • Carbohydrates: <130 g / day or <26% of calorie intake

2. Atkins diet modification
  • Carbohydrates: 6% of calorie intake
  • Fat: 65% of calorie intake
  • Protein: 30% of calorie intake

3. Very low ketogenic diet carbohydrate (VLCKD)
  • Carbohydrates <30 g / day.

Several studies use carbohydrate limits <50 g / day. The low-carbohydrate consumption in the ketogenic diet leaves the body in a glucose deficient condition. As a result, the body will use other alternative energy sources, namely fatty acids, and ketones. These changes in metabolism underlie the ketogenic diet's effects on neurological, metabolic, cardiac, and obesity diseases.

Neurological Diseases

Unlike other cells, brain cells cannot use fatty acids as a source of energy. Brain cells use ketones instead of glucose. Ketones are thought to have abilities: as anticonvulsants, reduce neuron cells excitability, and affect neurotransmitters.

The ketogenic diet has proven effective in preventing seizures. A meta-analysis study found the ketogenic diet can reduce seizures in epilepsy patients by 30-40%. At present, research is more focused on looking for the ketogenic diet's side effects for people with epilepsy, especially for the growth and metabolism of patients.

1. Dementia
Limited research evidence shows the benefits of the ketogenic diet for improving memory in patients with mild-moderate mild cognitive impairment (MCI) and Alzheimer's. However, further research is needed regarding these benefits.

2. Parkinson
A 2005 study proved that the 28-day ketogenic diet could improve the motor function of Parkinson's patients. In that study, a hyper ketogenic diet with a carbohydrate ratio of 2%, 8% protein, and 90% fat was used.

That study also stated that two things might cause improvements in motor function. First, changing dietary patterns to the ketogenic diet can directly improve motor function. Second, the low consumption of protein can increase the levodopa's bioavailability to improve motor function. As a result, more research is needed before concluding that the ketogenic diet is beneficial for Parkinson's patients.

3. Glioma
A 2017 meta-analysis study also found that only two out of six studies showed the benefits of the ketogenic diet in patients with malignant gliomas. The remaining four studies state the benefits of the ketogenic diet are still inconclusive. Possible benefits of the ketogenic diet for malignant gliomas are reducing seizures, decreasing cancer progression, improving general conditions, and improving quality of life. Still, other studies are needed with better research methods and a greater number of samples.

4. Brain injury
The ketogenic diet is thought to reduce seizures due to traumatic brain injury. However, the anti-seizure effect is still being debated and requires further research.

Metabolic and Cardiovascular Diseases

The ketogenic diet has also been investigated for its benefits for the following metabolic and cardiovascular diseases:

1. Diabetes Mellitus type 2 (DM type 2)
In patients with type 2 DM, the ketogenic diet can increase insulin sensitivity and reduce plasma glucose and hemoglobin A1c (HbA1c) levels. Some research states that the ketogenic diet can reduce the dose of insulin needed, and even insulin injection can be stopped.

2. Dyslipidemia
Although fat consumption increases, cholesterol parameters in the ketogenic diet actually get better. Limitation of carbohydrate intake triggers the condition of ketosis which can change fat metabolism. Changes in fat metabolism are decreased total cholesterol levels, low-density lipoprotein cholesterol (LDL), triglycerides. Also an increase in high-density lipoprotein cholesterol (HDL).
The size and volume of LDL also increase so that atherogenicity decreases.

3. Cardiovascular Disease
The ketogenic diet causes a decrease in blood pressure, although it is not significant. This diet can also improve lipid profile and insulin sensitivity, which are risk factors for heart disease.

4. Obesity
The ketogenic diet is proven to reduce weight in obese patients. However, it is still not sure about the cause of weight loss. 

Other Diseases

Although the evidence gathered is not enough, the ketogenic diet is thought to be beneficial for the following diseases:

1. Polycystic Ovary Syndrome (PCOS)
In PCOS patients, the ketogenic diet can reduce free testosterone levels, LH / FSH ratio, fasting insulin, and body weight.

2. Acne
In theory, the ketogenic diet can reduce the severity and progression of acne. This ability is associated with decreased insulin secretion and insulin-like growth factor-1 (IGF-1). Insulin and IGF-1 trigger:
  • the keratinocyte proliferation and abnormal follicular epithelium desquamation,
  • increase oil production,
  • the Propionibacterium acnes colonization.

3. Cancer
Molecularly, the ketogenic diet inhibits tumor cell growth due to low blood glucose levels, insulin secretion, and IGF-1. The hormones insulin and IGF-1 are involved in signaling cascades for cell growth, including tumor cells.

Side Effects of Ketogenic Diet

The ketogenic diet's short-term side effects are vomiting, gastroesophageal reflux disease (GERD), acidosis, excessive ketosis, constipation, fatigue, and hypocalcemia. Meanwhile, the ketogenic diet, in low-term, can have side effects on the kidneys and bones.

Many interpret that the ketogenic diet is a diet low in carbohydrates, high in fat and protein. Excessive consumption of protein can cause kidney damage. This occurs due to high levels of nitrogen that are excreted through the kidneys.

Several studies have shown that individuals who previously had healthy kidneys can adapt to high-protein diets. Conversely, individuals who already suffered from renal insufficiency (even asymptomatic) had kidney transplants or had kidney disease, metabolic syndrome, and obesity more prone to kidney damage. One form of kidney function disorder that often occurs in blood pressure control disorders resulting in hypertension. But these side effects are still being debated. Some studies have found no correlation between high-protein diets and kidney damage in high-risk subjects.