Imagine watching Evander Holyfield square off against Mike Tyson II, or even Tom Brady play a Superbowl against Peyton Manning. Both individuals are considered “the best of the best,” but at the end of the day, only one will come up victorious.
Recently, researchers at Stanford University decided to put the ketogenic diet against the Mediterranean diet in a head-to-head study looking at which diet is “best.” Studies show several positive benefits for both the keto diet and the Mediterranean diet; however, some nutritionists and doctors prefer the Mediterranean diet due to its “less restrictive nature.” Before we dive into the details of the study, let’s give a brief overview of what each diet consists of and how they differ.
The Differences Between Keto and the Mediterranean Diet
The name of the highly regarded Mediterranean diet comes from its basis in traditional foods commonly eaten in countries bordering the Mediterranean Sea, such as France, Spain, Greece, and Italy. The diet commonly consists of fresh vegetables, fruits, legumes (i.e. lentils and chickpeas) as well as oats/cereals. In terms of macros, a Mediterranean diet typically consists about 35-40% calories from fat, 40-50% from carbohydrates, and 15-20% from protein.
In addition, the Mediterranean diet prioritizes higher fish intake over higher meat intake as well as incorporating cheese, yogurt, and red wine. Studies show several benefits of a Mediterranean diet on various markers of metabolic health, but especially cardiovascular health. This is likely due to prioritizing monounsaturated fats like extra virgin olive oil among other things.
The ketogenic diet was originally used for treatment of epilepsy and is now one of the most popular diets for body composition and brain performance across the world. The diet typically consists of higher amounts of fat (60-80%), moderate protein (15-30%), and low carbohydrates (5-10%). In last decade, an explosion of research has developed around the keto diet showing benefits far beyond just epilepsy and body composition. These benefits extending to areas such as Alzheimer’s, cancer, diabetes, and even autoimmune conditions.
So, What Did The Keto/Mediterranean Diet Study Look At?
The study under discussion looked at 33 middle-aged individuals with prediabetes and Type II diabetes over 12 weeks on each diet. The study design was a randomized crossover trial, meaning that the subjects were randomly assigned to one condition and then crossed over to the other condition.
In the keto diet group, participants were counseled to sustain nutritional ketosis by limiting carbohydrates to 20–50 g/day, keeping proteins to ∼1.5 g/kg ideal body weight/day, with the remaining kcals coming from fats. Participants were also instructed to consume >3 servings/day of non-starchy vegetables and maintain adequate mineral and fluid intake for the ketogenic state (sodium, 3–5 g/day; potassium, 3–4 g/day).
During the Mediterranean diet phase, participants were encouraged to follow the Mediterranean Diet Pyramid, with the additional restriction of avoiding added sugars and refined grains.
The instructions were to follow a mostly plant-based diet that included vegetables (including starchy vegetables); legumes; fruits; whole, intact grains; nuts; and seeds, with fish as the primary animal protein and olive oil as the primary fat. After the subjects were done with one condition, there was no washout period so they went right into eating the other diet. It’s important to note that during the first 4 weeks of each phase of the study, participants were given their meals by a meal preparation company and the last 8 weeks they had to make food on their own.
What Did the Study Find?
In short, the study found “no differences” between the two different diets. HbA1c, the primary study outcome, improved significantly for participants on both diets (Keto -9% and Med -7%), but was not significantly different between the keto and Mediterranean diets. However, there were 3 distinct differences:
1) Triglycerides decreased more in the ketogenic diet condition
2) LDL cholesterol increased more in the ketogenic diet condition
3) Average blood glucose decreased more in the ketogenic diet condition
Challenges of the Study
1) Done in the middle of COVID so reaching patients was difficult
2) 12 of the participants did not receive delivered food for the first 4 weeks of their second phase of the crossover.
3) Subjects had to self-report weight from home
4) Everyone was in a caloric deficit during the first 4 weeks in which meals were provided.
5) No washout period between diets.
6) Mediterranean group didn’t eat wheat during first 4 weeks since meal preparation company was wheat and dairy free.
7) Average A1C was 6.0 (right past the line of pre-diabetic) so it’s hard to see drastic drops there.
8) LDL in KD group was 15 points lower to start and only raised 15 -20 points so not a huge shift, yet this result was a major focus point for researchers and critics.
Key Takeaways from the Study Comparing the Keto and Mediterranean Diets
Overall, we say kudos to these researchers for attempting to tackle a study like this in the middle of COVID which is extremely difficult to do. However, there are several challenges of the study, such as the 4 weeks of meals for the individuals along with an exaggeration of the “bad LDL” rises in the keto group with a lack of focus on other important markers. For example, the researchers did not look at lipid size, which is way more important than total LDL. Moreover, total LDL is a poor marker by itself of cardiovascular risk and should be taken in a more holistic view. Perhaps there is some benefit for those more concerned with cholesterol levels to alternate between periods of being in ketosis and then switching to a more Mediterranean style of eating.
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