In a recent review published in the journal Diabetes Treatment, researchers weighed the evidence on ketogenic diets and their effectiveness for treating type 1 diabetes (T1D), type 2 diabetes (T2D), and gestational diabetes (GD). Their findings suggest that many questions about this topic remain unresolved and that much further research is needed before ketogenic diets can be included in clinical practice guidelines for diabetes.
Study: Does a ketogenic diet have a place in diabetes clinical practice? Review of current evidence and controversysmall. Image credit: Chinnapong / Shutterstock
A growing global burden of diabetes
Diabetes, which results from impaired glucoregulatory control and the associated state of hyperglycemia, is a prevalent chronic disease worldwide. An estimated 108 million people were living with diabetes in 1980. This number has grown to more than 462 million today.
Different forms of diabetes have different treatment protocols. For T2D, doctors may aim for drug-free remission or encourage management of a person’s glycated hemoglobin (HbA1c) to less than 7% or 53 mml/mol. This can be achieved through lifestyle changes such as increased activity and dietary modifications to maintain a target weight. For T1D, the condition is metabolically irreversible and must be treated medically with insulin. However, diets can complement medical treatment.
Dietary modifications for the treatment of diabetes
A key component of diabetes management is weight loss of 15 kg, which has been associated with improvements in glycemic control. In particular, there is still some uncertainty about dietary recommendations for people with diabetes who are already at a healthy weight.
For both T1D and T2D, the guidelines recommend diets rich in whole grains, fruits, vegetables, nuts, legumes, and fish, and a reduction in artificial sweeteners, processed meats, and refined carbohydrates. Diabetic people are often told to eat a high fiber diet and limit their intake of saturated fat.
Typically, lifestyle interventions lead to modest temporary reductions in body weight, which are not sufficient to encourage diabetes remission. This has led to interest in ketogenic or low-carbohydrate diets as a supplement to medical treatments such as insulin. These diets are also characterized by high fat intake and moderate protein intake. However, conflicting evidence and a lack of long-term data have precluded the inclusion of the ketogenic diet in diabetes management guidelines.
In the present review, researchers conducted a literature search through major medical databases such as Medline, Scopus and PubMed using the search terms ‘ketogenic’, ‘low carb’ and ‘very low carb’.
Evidence on the efficacy of low-carbohydrate and ketogenic diets
Ketogenic diets aim to achieve a blood ketone level of 0.5 to 3 mg/dL. They can be of various kinds depending on how limited the carbohydrate intake is. Some diets use grams to measure daily carbohydrate consumption, while others use the percentage of daily energy that comes from carbohydrates.
High-carbohydrate foods such as potatoes, cereals, rice and bread are often replaced by high-fat animal proteins. However, consuming too much protein can reduce the effectiveness of the diet. Carbohydrate levels consumed are based on the assumption that adults consume 2000 kcal per day, which may not be accurate. These inconsistencies make it difficult to generalize findings from different studies.
The ketogenic diet has been credited with rapid weight loss, but the physiological mechanisms are unknown. This could be due to reduced appetite and greater satiety while following ketogenic diets. Scientists have not resolved whether these diets are beneficial in terms of insulin sensitivity and glycemia.
Short-term studies lasting 15 to 32 weeks found that diabetics who followed a low-carb diet showed significant improvements in HbA1c and increased weight loss, and that many reduced their intake of antidiabetic drugs. Another study found that people with T2D reduced or stopped using insulin after following a low-carb diet for more than a year. There is also some evidence that ketogenic diets can improve blood pressure, preserve muscle mass, reduce fat mass and inflammation in people with diabetes, and promote an overall better quality of life.
Unanswered questions and need for further research
There are no long-term studies on whether the benefits of the ketogenic diet remain. Furthermore, there is doubt as to whether these benefits are primarily due to weight loss and could be achieved through any other effective nutritional program, such as a hypocaloric, very low-carbohydrate diet. There has been limited investigation into whether ketogenic diets can benefit people with T2D with a healthy body mass index (BMI).
Ketogenic diets can also have specific adverse effects. They are high in saturated fat and processed meats, which can increase the risk of heart disease. In addition, high-protein diets can reduce kidney health. They may lead to changes in calcium and bone metabolism in children and adults, increasing the risk of bone fractures in certain populations.
Whether ketogenic diets are appropriate for pregnant women with gestational diabetes has not been evaluated. Since they are high in animal protein, they must be modified to be relevant for people following vegetarian and vegan diets. Focusing on the quality of carbohydrates consumed can be helpful, rather than eliminating them completely.
Researchers have also noted that adherence and high dropout rates are a challenge for many low-carb dieters. In order to promote compliance and achieve safe and optimal results, the ketogenic diet should be carefully monitored and adjusted as needed. However, the lack of a universally accepted definition of the ketogenic diet is a barrier to the research and implementation of ketogenic diets for diabetes management.
