Low-Calorie, High-Protein Ketogenic Diet Versus Low-Calorie, Low-Sodium, and High-Potassium Mediterranean Diet in Overweight Patients and Patients with Obesity with High-Normal Blood Pressure or Grade I Hypertension: The Keto–Salt Pilot Study

Background and Objective: Dietary interventions are the first-line treatment for overweight individuals (OW) and individuals with obesity (OB) with high-normal blood pressure (BP) or grade I hypertension, especially when at low-to-moderate cardiovascular risk (CVR). However, current guidelines do not specify the most effective dietary approach for optimising cardiovascular and metabolic outcomes in this population. This study aimed to compare the effects of a low-calorie, high-protein ketogenic diet (KD) vs. a low-calorie, low-sodium, and high-potassium Mediterranean diet (MD) on BP profiles assessed via ambulatory BP monitoring (ABPM), as well as on anthropometric measures, metabolic biomarkers, and body composition evaluated by bioelectrical impedance analysis (BIA). Methods: This prospective observational bicentric pilot study included 26 non-diabetic adult outpatients with central OW status or OB status (body mass index, BMI > 27 kg/m2) and high-normal BP (≥130/85 mmHg) or grade I hypertension (140–160/90–100 mmHg), based on office BP measurements. All participants had low-to-moderate CVR according to the second version of the systemic coronary risk estimation (SCORE2) and were selected and categorized as either KD (n = 15) or MD (n = 11). Comprehensive blood analysis, BIA, and ABPM were conducted at baseline and after three months. Results: At baseline, no significant differences were observed between the groups. Following three months of dietary intervention, both groups exhibited substantial reductions in body weight (KD: 98.6 ± 13.0 to 87.3 ± 13.4 kg; MD: 93.8 ± 17.7 to 86.1 ± 19.3 kg, p < 0.001) and waist circumference. Mean 24 h systolic BP (SBP) and diastolic BP (DBP) significantly declined in both groups (24 h mean SBP decreased from 125.0 ± 11.3 to 116.1 ± 8.5 mmHg (p = 0.003) and 24 h mean DBP decreased from 79.0 ± 8.4 to 73.7 ± 6.4 mmHg (p < 0.001)). Fat-free mass (FFM) increased, whereas fat mass (FM), blood lipid levels, and insulin concentrations decreased significantly. The ΔFM/ΔFFM correlates with ABP improvements. However, no significant between-group differences were detected at follow-up. Conclusions: The KD and the MD mediated weight loss and body composition changes, effectively improving bio-anthropometric and cardiovascular parameters in individuals with OW status or OB status and high BP. Although more extensive studies are warranted to elucidate potential long-term differences, our findings suggest the manner in which these two different popular dietary approaches may equally confer metabolic and cardiovascular benefits, emphasising the importance of weight and FM loss.