By: Holden Adkins, Lagniappe Wellness Dietetic Intern

Diets are not immune to the cyclic nature of social trends. What’s old is new, and in 2024 carbs are as much a social taboo as last year’s high-waisted denim. Like most trends, an underlying marketing force drives public interest, and the marketing machine behind very low carb diets such as the keto diet has never been stronger. For people living with diabetes, this can become a tempting option. For a population that has to plan life around careful attention to carbohydrate intake, the idea of simply eliminating carbs altogether seems almost too simple and easy a solution. Social media personalities often present very low carb diets as a magic cure for diabetes, and this message is reinforced by persistent advertising for low-carb products. On the other hand, some alarmists warn that a diet based around elevating ketones could be dangerous or even deadly for people with diabetes. Thus, this bombardment of information needs to be disseminated in a way that is responsibly thorough and compares the diet to more traditional approaches. 

It’s important first to define what a very low carbohydrate or ketogenic diet (LCKD) is. In very basic terms, carbs, or sugars, are the preferred fuel for the body. However, when a diet does not supply carbs, most of the cells in the body break down fat to supply themselves with energy. However, this does not work for the brain. Instead, some fat is converted to a type of molecule called ketones, which is used to fuel the brain as well as the kidneys, heart, and muscle.

The beauty of a very low carbohydrate diet for diabetes treatment is the simplicity. The learning curve that comes with a diabetes diagnosis is daunting to say the least. Patients have to quickly learn how to monitor their carbohydrate intake, how to attenuate the absorption of carbs, and in those that are insulin-dependent, how to calculate insulin needs from carb intake. Virtually eliminating carbs altogether simplifies the entire curriculum to identifying and avoiding carbs. This has the potential to greatly reduce the knowledge-deficit induced stress and anxiety on the patient, and lower stress alone can vastly improve blood sugar management.

The current body of literature does clearly indicate that a very low carbohydrate diet can be effective in managing blood sugar. A 2005 study examined 28 subjects with type 2 diabetes treated with a ketogenic diet. 81% of participants were able to reduce or eliminate their dependence on diabetes medications. (1) Further, a 2009 rat study found that rats with diabetes placed on a ketogenic diet were able to achieve near-normal blood sugar levels. (2) For a more recent example, a 2021 systematic review of relevant literature found that ketogenic diets consistently showed greater success in reducing diabetic dependence on medication when compared to a control diet. (3) If the question is simply one of efficacy, these very low carb diets are demonstrably viable.

HbA1c demonstrated a mean decrease of 1.1% in one study where ketogenic diets were prescribed to people with diabetes. Source: Yancy, William S, et al. “A Low-Carbohydrate, Ketogenic Diet to Treat Type 2 Diabetes – Nutrition & Metabolism.” BioMed Central, BioMed Central, 1 Dec. 2005

A scrupulous evaluation of the diet, however, should weigh it against more common medical nutrition therapy for diabetes. For example, the aforementioned rat study only weighed the ketogenic diet against a typical diet and a high carb diet, rather than against a traditional therapeutic protocol for diabetes. Luckily, there are quite a few studies comparing these diets to traditional diets. A 2012 study allowed 362 obese test subjects, 102 of whom had type 2 diabetes, to choose between a low calorie and low carbohydrate diet. After 24 weeks, participants using the ketogenic diet demonstrated better glycemic control than those on a low calorie diet alone. (4)

While all the research this article has examined so far has reflected very positively on ketogenic diets, it is important to consider the type of research being cited. All the aforementioned research has involved controlled trials with relatively small sample groups. Several have also demonstrated notable issues with sampling, for example the subject populations being able to choose their own intervention in the previously mentioned research. The gold standard in a situation like this would be to turn to randomized control trials (RCTs). However, RCTs are particularly difficult to implement in nutrition research, because the very nature of the variable intervention makes limiting confounding variables a challenge. In 2020, a literature review in Practical Diabetes reviewed all relevant literature for RCTs comparing ketogenic diets to other diet protocols for the treatment of diabetes. The review only found two relevant studies, of which only one demonstrated a significant reduction in HbA1c with a ketogenic diet compared to a traditional reduced calorie diet. (5) Unfortunately, this means the unavoidable conclusion is that the current research is inadequate to endorse a ketogenic diet as more effective than a reduced calorie diet.

The American Diabetes Association Standards of Care Manual does recommend reducing overall carbohydrate intake for diabetes management, and acknowledges that this can be applied in quite a few different ways. The manual also acknowledges low carbohydrate diets as an effective method of weight loss, but clarifies that no specific eating pattern has consistently demonstrated superior long term weight management efficacy. (7) The ADA manual states that “carbohydrate-restricted eating patterns…were effective in reducing A1C in the short term (<6 months), with less difference in eating patterns beyond 1 year.” The ADA also acknowledges that current research indicates challenges to sustainability with low carb diets. Additionally, it cautions that very low carb diets should not be used for children, people who are lactating, or are at risk of renal disease or disordered eating, and that it can increase the risk of ketoacidosis in patients who are using SGLT2 inhibitors (7).

One of the other chief concerns for a ketogenic diet is sustainability. Ketogenic diets are inherently extremely restrictive. This is difficult to evaluate since most research is only carried out over the course of a few months. However, some research indicates that the benefits seen in the first year of a ketogenic diet are no longer seen during periods longer than one year. (6) 

Ketogenic diets are a tempting nutrition intervention for type-2 diabetes. The research is fairly clear that the diet can absolutely be very effective in normalizing blood sugar and improving HbA1c. However, there is insufficient evidence to conclude that these diets are superior to traditional nutrition therapies, such as reducing calories. Additionally, a ketogenic diet comes with extra sustainability concerns. Because of this, ketogenic diets should not be a default or first line treatment, but should be considered as an alternative therapy if it fits the particular wants and needs of the patient. 

Sources: 

1. Yancy, William S, et al. “A Low-Carbohydrate, Ketogenic Diet to Treat Type 2 Diabetes – Nutrition & Metabolism.” BioMed Central, BioMed Central, 1 Dec. 2005, nutritionandmetabolism.biomedcentral.com/articles/10.1186/1743-7075-2-34. 
2. Changes in dietary habits influence the glycemic level. Preliminary studies using the low-carbohydrate ketogenic diet (LCKD) were found to be quite promising in controlling diabetes mellitus. Therefore, et al. “Therapeutic Role of Low-Carbohydrate Ketogenic Diet in Diabetes.” Nutrition, Elsevier, 8 Oct. 2009, http://www.sciencedirect.com/science/article/abs/pii/S0899900709001774.&nbsp;
3. Tinguely, D., Gross, J. & Kosinski, C. Efficacy of Ketogenic Diets on Type 2 Diabetes: a Systematic Review. Curr Diab Rep 21, 32 (2021). https://doi.org/10.1007/s11892-021-01399-z
4. Talib A. Hussain, Thazhumpal C. Mathew, Ali A. Dashti, Sami Asfar, Naji Al-Zaid, Hussein M. Dashti, Effect of low-calorie versus low-carbohydrate ketogenic diet in type 2 diabetes, Nutrition, Volume 28, Issue 10, 2012, Pages 1016-1021,ISSN 0899-9007, https://doi.org/10.1016/j.nut.2012.01.016.
5. Dyson, P. (2020), Very low carbohydrate ketogenic diets and diabetes. Pract Diab, 37: 121-126. https://doi.org/10.1002/pdi.2284
6. Batch, Jennifer T, et al. “Advantages and disadvantages of the Ketogenic Diet: A review article.” Cureus, 10 Aug. 2020, https://doi.org/10.7759/cureus.9639.&nbsp;
7. American Diabetes Association Professional Practice Committee; 5. Facilitating Behavior Change and Well-being to Improve Health Outcomes: Standards of Medical Care in Diabetes—2022. Diabetes Care 1 January 2022; 45 (Supplement_1): S60–S82. https://doi.org/10.2337/dc22-S005