Ketogenic diets and diabetes: A promising match or a questionable pair?

By Priyanjana Pramanik, MSc.Reviewed by Susha Cheriyedath, M.Sc.Nov 16 2023

In a recent review published in the journal Diabetes Therapy, researchers weighed the evidence regarding ketogenic diets and their efficacy for the treatment of type 1 diabetes (T1D), type 2 diabetes (T2D), and gestational diabetes (GD). Their findings indicate that many questions on this subject remain unresolved and that many further investigations are needed before ketogenic diets are included in clinical practice guidelines for diabetes.

Study: Does a Ketogenic Diet Have a Place Within Diabetes Clinical Practice? Review of Current Evidence and Controversies. Image Credit: Chinnapong / Shutterstock

An increasing global burden of diabetes

Diabetes, which results from compromised glucoregulatory control and the associated condition of hyperglycemia, is a prevalent chronic disease globally. An estimated 108 million people lived with diabetes in 1980; this number has grown to more than 462 million today.

Different forms of diabetes have distinct treatment protocols. For T2D, doctors may target drug-free remission or encourage the management of an individual’s glycated hemoglobin (HbA1c) at less than 7% or 53mml/mol. This can be achieved through lifestyle changes, such as increased activity and dietary modifications, to maintain a target weight. For T1D, the condition cannot be reversed metabolically and must be treated medically with insulin; however, diets can complement medical treatment.

Dietary modifications for diabetes treatment

A fundamental component of diabetes management is reducing weight by 15 kg, which has been associated with improvements in glycemic control. Notably, there is still some uncertainty on dietary recommendations for individuals with diabetes who are already at a healthy weight.

For both T1D and T2D, guidelines recommend diets rich in whole grains, fruits, vegetables, nuts, pulses, and fish and a reduction in artificial sweeteners, processed meats, and refined carbohydrates. Diabetic individuals are often told to consume high fiber and limit their saturated fat intake.

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 to complement medical treatments such as insulin. These diets are also characterized by high fat intake and moderate protein intake. However, conflicting evidence and the lack of long-term data have precluded ketogenic diets from being included 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 carbohydrate,’ and ‘very low carbohydrate.’

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 restricted carbohydrate intakes are. Some diets use grams to measure daily consumption of carbohydrates, while others use the percentage of daily energy derived from carbohydrates.

High-carbohydrate foods, such as potatoes, grains, rice, and bread, are often replaced by animal proteins high in fat. However, excessive protein consumption can reduce the efficacy of the diet. The 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 because of decreased appetite and greater satiety while following ketogenic diets. Scientists have not resolved whether these diets are beneficial regarding insulin sensitivity and glycemia.

Short-term studies over 15 to 32 weeks found that diabetic people who followed a low carbohydrate diet showed marked improvements in HbA1c and increased weight loss and that many reduced their intake of anti-diabetic medications. Another study found that people with T2D reduced or discontinued insulin use after following a low-carbohydrate diet for over a year. There are also some indications that ketogenic diets can improve blood pressure, preserve muscle mass, reduce fat mass and inflammation in individuals with diabetes, and promote an overall better quality of life.

Unanswered questions and the need for further research

There are no long-term studies on whether the benefits of ketogenic diets persist. Furthermore, there are doubts about whether these benefits are primarily driven by weight loss and could be achieved through any other effective diet plan, such as a hypocaloric, very low carbohydrate diet. There has been limited exploration on whether ketogenic diets can benefit individuals with T2D with a healthy body mass index (BMI).

Ketogenic diets may also have specific adverse effects. They are high in saturated fats and processed meats, which may increase the risk of heart disease. Moreover, high-protein diets may reduce kidney health. They may result in changes in calcium and bone metabolism in children and adults, increasing the risk of bone fractures in some populations.

Whether ketogenic diets are suitable for pregnant women with gestational diabetes has not been assessed. Since they are high in animal protein, they must be modified to be relevant for people who follow vegetarian and vegan diets. Focusing on the quality of carbohydrates consumed may be helpful, rather than eliminating them altogether.

Researchers have also noted that adherence and high dropout rates are a challenge for many followers of low-carbohydrate diets. In order to promote adherence and achieve safe and optimal outcomes, the ketogenic diet should be monitored carefully and adjusted as necessary. However, the lack of a universally acceptable definition for ketogenic diet is a barrier to research and implementation of ketogenic diets for the management of diabetes.