Pitting a ketogenic diet against a Mediterranean diet in pre-diabetes and Type 2 diabetes patients, scientists have learned that both confer metabolic benefits, but “keto” also has a darker side [1].
Diabetes is often reversible with diet
While many anti-diabetes drugs have been developed in recent decades, with some being repurposed as anti-aging drugs [2], there is a growing understanding that Type 2 diabetes can be prevented and even reversed with the help of a healthy diet [3].
However, there is an ongoing battle between diets, such the ketogenic diet and the Mediterranean diet. The latter is less restrictive, more balanced, and arguably has greater scientific evidence behind it [4], while the former touts inducing the state of ketosis, the metabolic switch from carbohydrates to fat as the body’s main energy source, as its main advantage.
“Keto” is thought to be quite effective when it comes to weight loss, but since it derives most calories from animal protein and fat (although some rather convoluted vegan variants exist), it is suspected of raising cholesterol levels, including LDL, a form of cholesterol with largely harmful effects.
Keto vs Med
In this new study, the researchers directly pitted those two diets against each other in people with pre-diabetes and Type 2 diabetes. The study consisted of two arms, numbering 16 and 17 participants, with a median age of 60 years and a median BMI of 30. Both arms started with one diet, either the ketogenic or the Mediterranean, and switched to the other diet after 12 weeks for another 12 weeks. At the end of the study, there were 12 additional weeks of follow-up.
With diets, the devil is in the details; for instance, foods packed with empty calories, such as French fries, can be part of a vegan diet. To account for this, the researchers tried to make the two diets as healthy as possible. They used a well-formulated ketogenic diet (WFKD) and encouraged the participants on the Mediterranean diet to enhance it by completely avoiding refined sugars and grains (Med-Plus).
According to the researchers, both diets incorporate three key nutrition principles endorsed by diabetes organizations worldwide: including non-starchy vegetables, restricting added sugars, and limiting refined grains. The main differences between the two involve legumes, fruits, and whole grains, which are avoided in the ketogenic diet but are more than welcome in the Mediterranean diet.
During the keto phase, participants had to sustain ketosis by limiting carbohydrates to 20–50 grams per day and keeping protein consumption at about five grams per one kilogram of body weight per day, with all other calories coming from fats. During the Mediterranean phase, participants followed a mostly plant-based diet consisting of vegetables (including starchy vegetables), legumes, fruits, whole grains, nuts, and seeds, with fish as the primary source of animal protein and olive oil as the primary source of fat. In both phases, the participants were strongly advised against consuming any processed foods.
Participants were also advised to eat ad libitum, that is, without limiting calorie intake. Despite that, on average, participants on both diets lost weight. The weight loss was stronger with the ketogenic diet.
The pros and the cons
The researchers hypothesized that after 12 weeks on each diet, glycated hemoglobin (HbA1c), a standard measure of blood sugar, would similarly improve from baseline due to shared dietary characteristics but that the keto diet would increase some health risks due to the lack of legumes, fruits, and whole grains.
The results matched the expectations. Both diets led to similar decreases in HbA1c levels, even though participants on WFKD had been consuming 50% fewer carbohydrates compared to participants on Med-Plus. However, the ketogenic diet led to a more significant decrease in triglyceride levels (16% vs 5% for the Mediterranean diet).
The ketogenic diet also resulted in a substantial increase in LDL cholesterol (+10% vs -5% for the Mediterranean diet). While some resent research suggests that not all LDL cholesterol is equally bad [5], the researchers interpreted the rise in LDL cholesterol as a health risk.
The nutrient balance was generally worse under the ketogenic diet. It led to greater decreases in essential nutrients than the Mediterranean diet, including in fiber, folate, vitamin C, and magnesium, which the researchers attribute to the exclusion of legumes, fruits, and whole grains.
There were no substantial differences in adherence to and in satisfaction from both diets during the study. Interestingly, participants tended to give higher marks to whatever diet they had started with. However, during the follow-up period, when all restrictions were off, the participants’ diet bore a greater resemblance to Med-Plus than to WFKD, suggesting that the former might be easier to adhere to.
Conclusion
The results of this comparative study are generally in line with previous research. Both diets produced considerable metabolic benefits for people with pre-diabetes and Type 2 diabetes. However, there were obvious trade-offs: the ketogenic diet was more effective in decreasing weight and triglyceride levels, but it also raised LDL cholesterol and restricted essential nutrients such as fiber. Larger studies are probably needed to supply more definitive answers.
Literature
[1] Gardner, C. D., Landry, M. J., Perelman, D., Petlura, C., Durand, L. R., Aronica, L., … & Kim, S. H. (2022). Effect of a Ketogenic Diet versus Mediterranean Diet on HbA1c in Individuals with Prediabetes and Type 2 Diabetes Mellitus: the Interventional Keto-Med Randomized Crossover Trial. The American Journal of Clinical Nutrition.
[2] Harrison, D. E., Strong, R., Alavez, S., Astle, C. M., DiGiovanni, J., Fernandez, E., … & Miller, R. A. (2019). Acarbose improves health and lifespan in aging HET3 mice. Aging Cell, 18(2), e12898.
[3] Taheri, S., Zaghloul, H., Chagoury, O., Elhadad, S., Ahmed, S. H., El Khatib, N., … & Abou-Samra, A. B. (2020). Effect of intensive lifestyle intervention on bodyweight and glycaemia in early type 2 diabetes (DIADEM-I): an open-label, parallel-group, randomised controlled trial. The lancet Diabetes & endocrinology, 8(6), 477-489.
[4] Martínez-González, M. A., Gea, A., & Ruiz-Canela, M. (2019). The Mediterranean diet and cardiovascular health: A critical review. Circulation research, 124(5), 779-798.
[5] Ivanova, E. A., Myasoedova, V. A., Melnichenko, A. A., Grechko, A. V., & Orekhov, A. N. (2017). Small dense low-density lipoprotein as biomarker for atherosclerotic diseases. Oxidative medicine and cellular longevity, 2017.
