Comparative Effects of Time-Restricted Eating and the Ketogenic Diet on QRISK3-Assessed Cardiovascular Risk in Individuals with Obesity: A Longitudinal Analysis of Metabolic, Anthropometric and Lifestyle Factors

Background: /Objectives: Obesity is a growing public health issue, particularly among young adults, with long-term dietary strategies still under debate. This study evaluates the impact of the ketogenic diet (KD) and time-restricted eating (TRE) on QRISK3 cardiovascular risk scores over three months in individuals with obesity. Methods: Forty-nine participants were assigned to either a KD (n=23) with a controlled macronutrient composition or TRE (n=26) without specific macronutrient distribution. A certified clinical nutritionist prescribed and monitored the dietary interventions. Anthropometric measurements, body composition analysis, and QRISK3 scores were assessed at baseline and after 12 weeks to evaluate cardiovascular risk modifications. Results: Both interventions significantly reduced BMI (TRE: p < 0.001, KD: p < 0.001), waist circumference (WC) (TRE: p < 0.001, KD: p < 0.001), and waist-to-hip ratio (WHR) (TRE: p < 0.001, KD: p < 0.001). However, the KD led to superior metabolic improvements, including increased HDL-C (p < 0.001) and a lower TC/HDL-C ratio (p < 0.001), while TRE showed no significant HDL-C changes (p = 0.30). Systolic blood pressure improved significantly only in the KD group (p < 0.001). QRISK3 scores declined in both groups (TRE: p = 0.05, KD: p < 0.001), with a greater reduction in KD. Linear regression (adjusted R² = 0.975) identified baseline QRISK (p < 0.001) as the strongest predictor of final QRISK scores, while fasting glucose (p = 0.015) and atrial fibrillation (p = 0.048) were associated with increased cardiovascular risk. Interaction analysis (adjusted R² = 0.495) showed that older participants in the KD group experienced a more pronounced QRISK reduction (p = 0.011); Conclusions: The ketogenic diet proved to be more effective than time-restricted eating in reducing cardiovascular risk, improving lipid profile, and enhancing glycemic control. These findings support KD as a superior dietary intervention for individuals with obesity and metabolic dysfunction.