A ketogenic diet has been shown to be effective for improving blood glucose control and helping towards weight loss in people with diabetes. It has also been shown to significantly benefit a number of other conditions.
Whilst the benefits are clear in some conditions, such as epilepsy, in which the ketogenic diet has been extensively studied.
In other conditions, the ketogenic diet shows promise but there is a lack of robust clinical trials to give strong evidence.
Epilepsy and seizure disorders
The ketogenic diet is one of the medically accepted treatment for chronic seizures in epilepsy and other epileptic disorders, including Lennox-Gastaut syndrome and Dravet syndrome. 
Research has shown that it helps reduce the frequency of seizures in children.
About half the children whose seizures don’t respond to any medications almost immediately stop seizure activity once they are in ketosis. 
The reason for the effectiveness of ketogenic diets in treating children is not entirely clear. Researchers are investigating this approach in adults.
Scientists don’t know whether the seizure activity is improved by the presence of the ketone B-OHB (beta-hydroxyburyrate) or the stark reduction in blood glucose or insulin in the body. It could that this results from a combination of these factors or something altogether different.
By producing a state of ketosis, the ketogenic diet may have a role in helping to treat aggressive metastatic cancers and brain tumours that are not treated effectively with standard care alone.
Sugar is a fuel source which can feed cancer and insulin is essentially a growth hormone. The ketogenic diet can dramatically reduce carbohydrate, which helps reduce blood sugar and the amount of insulin in the body.
The theory states that this cuts down on the amount of sugar and insulin that certain cancers rely on and that malignant tumours can’t adapt readily to using ketones instead of sugar like normal tissue can. This is part of the Warburg effect. 
Whilst this is the theory, no significant studies have been run that have shown whether or not this effect occurs in practice and there is some evidence to suggest that cancers may adapt to using ketones. 
As a result, the benefits of a ketogenic diet on cancer is still an unknown area.
Alzheimer’s disease (AD) often manifests itself as the inability of certain regions of the brain to use sugar as a fuel. Thus, researchers are investigating whether uncontrolled type 2 diabetes, where too much sugar remains in the blood, could damage the brain and contribute to the development of AD. 
There is evidence that changing the body’s energy fuel from mainly sugar towards ketones may have a significant role in brain health and perhaps even Alzheimer’s treatment. 
Ketones, which the brain can use for over half of its fuel requirements, once carbohydrate intake is lowered, essentially boost the energy levels of brain cells by increasing the number of energy powerhouses (mitochondria) in these cells.
A higher number of mitochondria in brain cells is thought to help improve learning and memory abilities, leading to a better quality of life for people with AD. 
There’s evidence that a ketogenic diet could potentially help in preventing or combatting Parkinson’s disease.
In a very small, uncontrolled study, Parkinson’s disease patients experienced a mean of 43% reduction in Parkinson’s disease symptoms after following a ketogenic diet for 28 days. However, because the study was only seven participants, the researchers could not rule out the fact that the improvement may have been a placebo effect. 
Other research studies have suggested that ketones produced on a ketogenic diet may have beneficial effects on how the brain responds to dopamine, which could reduce the symptoms of the condition. 
More research will be needed though before we can say with any certainty whether the diet can indeed help.
Traumatic brain injury
Research suggest that a severe head trauma is often followed by the person having very-high blood sugars. There is some evidence that elevated blood sugar levels may worsen the injury and impair recovery from the trauma. 
Several compelling studies, in animal models and small clinical trials, tend to support that a ketogenic diet could protect against further damage from the injury by bringing blood sugar levels down  
Researchers who have tried to attenuate the effects of brain injury with ketones supplements have found that the brain’s uptake of ketones increases significantly following an injury, suggesting that the brain preferentially changes its fuel source during recovery. 
The mechanisms of action of ketones after an injury are unclear, but it is thought that they may lower inflammation in the brain and prevent brain cell death. It has been suggested that high ketone levels could also increase blood flow.
Recent research and controlled studies suggest that diet plays an important part in the management of attention-deficit/hyperactivity disorder (ADHD).
One of the diets that helps reduce symptoms associated with ADHD include the ketogenic diet.
The diet is especially thought to help with a symptom of ADHD overlapping with epilepsy called epileptiform discharges. 
In one study involving 37 children, treatment with the ketogenic diet resulted in a reduction of epileptiform discharges by 13.6 per cent in more than half of these children after only one month.
Further research needs to be done on the relationship between improvement of ADHD symptoms and eating ketogenic, but the diet can provide an alternative to stimulant medications, which can come with side effects.
Chronic Lyme disease symptoms
Lyme disease damages the brain by producing profound inflammation. Ketones may help alleviate some of the post-Lyme symptoms thanks to their significant anti-inflammatory effects.
Ketones bring down inflammation by reducing levels of cytokines – a commonly elevated inflammatory marker found in the brain of people affected by Lyme.
Providing ketones as a fuel source for the brain of people who have had Lyme may help speed up their recovery by lifting brain fog as well as improving memory and concentration.