The ketogenic diet is a high-fat, very low-carbohydrate eating pattern that changes how the body produces energy. By sharply reducing carbohydrate intake, the diet can cause the body to enter nutritional ketosis, a metabolic state in which it produces ketones from fat and uses them as an alternative fuel source.
Nutritional ketosis should not be confused with diabetic ketoacidosis, or DKA, a potentially life-threatening medical emergency. DKA occurs when there is not enough insulin for the body to use glucose properly, causing ketones to build up in the blood and make it acidic. It most commonly affects people with type 1 diabetes, although it can also occur in people with type 2 diabetes.
The distinction is important because the source material incorrectly suggests that people with ketoacidosis can use a ketogenic diet to increase ketones or treat the condition. Medical guidance instead identifies DKA as a condition requiring prompt medical treatment, typically involving fluids, electrolytes and insulin.
What is the ketogenic diet?
A ketogenic diet generally contains a high proportion of fat and very little carbohydrate. Protein intake is usually moderate rather than necessarily high, and the precise composition can vary depending on the type of ketogenic diet being used.
The diet has a well-established medical role in managing some forms of drug-resistant epilepsy, particularly in children, where it may be considered when other treatments have not adequately controlled seizures. Evidence reviews have found reductions in seizure frequency in some patients, although the treatment can also cause gastrointestinal and metabolic side effects and requires medical supervision.
It is not accurate to describe foods such as avocado, cheese, eggs or meat as foods that “contain ketones” that the body simply consumes for energy. Rather, the body produces ketones when carbohydrate availability is sufficiently low and it begins relying more heavily on fat for fuel.
What happens during ketosis?
Under normal conditions, the body relies heavily on glucose for energy. When carbohydrate intake is greatly reduced, the liver converts fatty acids into ketones, which can then be used by tissues as an alternative energy source.
This process is different from DKA. In nutritional ketosis, ketone production is controlled by the body’s normal metabolic processes. In DKA, a lack of effective insulin can lead to excessive ketone production and dangerous changes in blood acidity.
What does the evidence say about weight loss?
The ketogenic diet has been studied as a weight-loss approach, and research has found associations with reduced body weight in some adults. An umbrella review of randomized clinical trials found moderate-quality evidence for reductions in body weight, but it also found a clinically meaningful increase in LDL cholesterol in some ketogenic-diet groups. The authors said longer-term research is needed to determine whether short-term changes translate into better long-term health outcomes.
That means the diet should not be presented as a universally effective or risk-free way to lose weight. Harvard Health describes the ketogenic diet as a restrictive dietary approach with potential risks and notes that it is also used as a medical diet for epilepsy.
Possible side effects
Very low-carbohydrate diets can cause side effects including constipation, diarrhoea, nausea, headache, dizziness and fatigue. Restricting carbohydrates can also make it harder for some people to obtain adequate fibre and other nutrients, depending on what foods they choose.
Research into ketogenic diets for epilepsy has also reported gastrointestinal and metabolic adverse effects, while the appropriate duration and long-term safety of ketogenic diets remain areas of ongoing research.
People with diabetes need particular care because ketone accumulation can be a warning sign of DKA, especially when blood glucose is elevated. People with diabetes should follow their healthcare professional’s advice about diet, medication and ketone monitoring rather than treating DKA through dietary changes.
