June 3, 2025, 3:10 pm | Read time: 4 minutes
Mediterranean and ketogenic diets are two dietary approaches whose followers anticipate various health benefits, including weight management. Both diets are frequently the subject of scientific research. A new study has now analyzed the effects of both diets on cardiovascular risk factors. FITBOOK presents the findings.
The good reputation of the Mediterranean diet is based on numerous studies that have examined its positive health effects. This diet is characterized by a high intake of valuable plant fats, high-quality protein (such as from fish), and fiber, and it is known to have a beneficial effect on blood pressure.1 It is also said to help achieve and maintain a healthy weight. Similarly, the ketogenic diet is believed to support weight loss goals. How do the two diets compare directly when it comes to avoiding cardiometabolic risk factors? An Italian research team has investigated this.2
Overview
Mediterranean vs. Keto: Study on the Effects of the Diets
The prevalence of overweight and obesity is high worldwide and continues to rise, as the study authors write. In particular, the accumulation of visceral fat is associated with various health risk factors. To avoid these, lifestyle changes are recommended—not least in diet. “Many of these recommendations align with the basic principles of the Mediterranean diet,” the report continues. This diet is associated with a lower incidence of cardiovascular events and lower overall mortality. Recently, however, interest in ketogenic diets has grown due to their potential for weight reduction and treatment of metabolic syndrome. The researchers wanted to find out whether these diets might better support metabolism and the cardiovascular system than traditional diets with general calorie reduction.
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Details of the Study
The study involved 26 adults, some of whom were overweight and some obese. Some had high-normal blood pressure (values in the upper normal range), while others had grade 1 hypertension. The distribution among the participants is not known. Overall, the predominantly male study participants had low to moderate cardiovascular risk scores.
The participants were randomly assigned to two groups. The keto group, consisting of 15 participants, was to follow a calorie-reduced, protein-rich diet with very low carbohydrate content during the three-month study period. Participants in the Mediterranean diet group were instructed to follow a calorie-reduced diet with low sodium and high potassium content. This diet was to be rich in healthy fats, fiber-rich vegetables, whole grains, and fruits.
To assess the effects of each diet, the researchers examined the participants at the beginning of the intervention and again after three months. In addition to body weight, they measured blood pressure and various blood values. They also analyzed body composition, specifically the proportion of fat mass to lean mass, including muscle tissue.
Mediterranean and Ketogenic Diets Have Positive Effects
After three months, the researchers observed significant improvements in both groups. In the keto group, participants’ body weight decreased by an average of about 11 kilograms, while in the Mediterranean group, participants also experienced a reduction in waist circumference. Additionally, the researchers documented improved blood lipid levels and more favorable insulin responses.
Body composition analysis showed a decrease in fat mass and an increase in lean mass. Interestingly, the participants’ blood pressure improved more significantly the more body fat they lost relative to muscle mass. On average, systolic blood pressure decreased from 116 mmHg to 116 mmHg, and diastolic blood pressure from 79 to 74 mmHg. These observations were made equally in both the keto and Mediterranean groups.
… with one exception
The researchers found only one significant difference. The participants on the ketogenic diet experienced a more pronounced nighttime drop in blood pressure—a phenomenon known in science as “nocturnal dipping.”3 In healthy individuals, blood pressure drops by between 10 and 20 percent during sleep. A lack of dipping can be an indicator of an increased risk of cardiovascular disease. In this regard, the ketogenic diet performs slightly better than the Mediterranean diet, as it appears to more reliably support the natural day-night rhythm of blood pressure. However, it was associated with side effects (such as constipation and headaches), especially in the early phase of the study.
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Limitations of the Results
The study provides evidence that both the ketogenic and Mediterranean diets have a positive effect on various health parameters in cases of existing (severe) overweight, including blood pressure. However, a longer observation period would be necessary to assess the long-term effects of the diets. Additionally, the sample size was very small, with only 26 participants. Furthermore, the participants’ adherence to the diet was not monitored, so it was not possible for the researchers to determine how strictly they followed the guidelines. Finally, a third control group was missing for evaluating the interventions.
Several questions remain open. FITBOOK has inquired whether changes in participants’ preferences or needs were recorded. Are there considerations on how the diets could be adapted to individual needs or preferences? Are follow-up studies planned? A response is still pending.