The ketogenic diet is attracting growing interest among people with type 2 diabetes because it would have benefits, among other things, on weight and glycemic control (blood sugar level). However, it is premature to recommend the adoption of the ketogenic diet to a diabetic person given the lack of knowledge about its medium and long-term effects. Like other highly restrictive diets, the ketogenic diet is difficult to maintain for more than a few months and can lead to overeating in response to deprivation.
What is the ketogenic diet?
The ketogenic diet, also called “very low carbohydrate diet” or “very low carb diet” contains mainly fat (lipids) and very few carbohydrates. According to studies, the carbohydrate content can vary between 20 and 50 g per day.. By way of comparison, the diet currently recommended for people with diabetes (conventional diet) and presented in the form of a balanced plate provides between 130 and 225 g of carbohydrates per day! The conventional diet provides enough carbohydrates to meet the brain’s needs, estimated at 130 g per day.
Adaptation of the body in a situation of severe carbohydrate restriction
To function throughout the day, the body needs energy from the food we eat. Normally, carbohydrates are its main source of energy. The brain is the exception because a natural barrier blocks access to lipids. In the event of severe carbohydrate restriction, as in the ketogenic diet, the brain must therefore resort to an alternative source of energy called “ketone bodies”.
During the first few days of a ketogenic diet, the body reacts by drawing its energy from the stores of glucose stored in the liver and the muscles. The use of these reserves releases a significant amount of water which is eliminated in the urine, resulting in temporary and rapid weight loss due to dehydration. Once glucose stores are depleted, the liver uses lipids and proteins to provide energy for the body. The breakdown of lipids by the liver generates ketone bodies which are primarily used to fuel the brain. Part of the ketone bodies are eliminated by breathing, which explains the “fruity” breath present in people who follow this diet.
Besides this unpleasant breath, some side effects usually occur during the first weeks after starting the ketogenic diet. The most commonly reported are fatigue, headaches, dizziness, nausea and muscle cramps. Hypoglycemia can also occur in some people with diabetes depending on their medications. 1 Constipation sets in quickly and persists due to lack of fiber. This problem is accentuated in the presence of insufficient hydration.
Effectiveness of the ketogenic diet
Many benefits are attributed to the ketogenic diet. However, several shortcomings in the studies reviewed limit the scope of the results obtained and make it difficult to evaluate this diet.
Lack of uniformity in the composition of the ketogenic diet with regard to the type of fat and protein to consume as well as the quantity of vegetables.
Some conventional diets tested did not meet recommendations and contained a significant proportion of refined starches and foods with added sugar.
Inability to verify whether the participants actually maintained their adherence to the assigned diet (ketogenic or conventional) until the end of the study.
Short-term studies, numerous biases, no distinction between diabetics and non-diabetics, absence of a control group, small number of participants, etc.
Effect on weight
When there is a significant restriction in calories, the ketogenic diet provides significant weight loss, comparable to that of other diets that are also very restrictive, over a period of 2 to 6 months. In this case, the weight loss observed in the ketogenic diet seems to be caused by the reduction in calories consumed, rather than by the restriction of carbohydrates. After 1 to 2 years, the weight losses observed are modest and similar for all these diets. The inability to maintain such diets beyond 6 months explains these results.