What this Trial Is About

Olive oil is a fundamental component of the Mediterranean diet and a major source of monounsaturated fatty acids with well-established cardioprotective properties. When rich in phenolic compounds-such as hydroxytyrosol, tyrosol, oleuropein, oleocanthal, oleacein, and ligstroside aglycone-it is considered a functional food with antioxidant, anti-inflammatory, cardioprotective, chemoprotective, and neuroprotective effects. According to EU Regulation 432/2012, daily consumption of 20 g of extra virgin olive oil containing at least 5 mg of hydroxytyrosol and tyrosol derivatives (250 mg/kg) contributes to the protection of blood lipids from oxidative stress and qualifies for a health claim. Overweight/obesity, characterized by excessive fat accumulation, is strongly associated with non-communicable diseases, including cardiovascular disease, type 2 diabetes, hypertension, certain cancers, and neurodegenerative disorders. Chronic low-grade inflammation and oxidative stress are key mechanisms underlying obesity-related metabolic disorders. Although dietary energy restriction remains the primary approach for weight management, growing research interest focuses on natural products rich in phenolic compounds as potential modulators of molecular pathways involved in central obesity. However, robust clinical evidence in humans with central obesity and metabolic abnormalities remains limited. Therefore, this double-blind, randomized, controlled trial aims to investigate the effects of extra virgin, high-phenolic olive oil (HPOO) compared with low-phenolic olive oil (LPOO) in adults with overweight/obesity with metabolic abnormalities. Participants will consume the assigned olive oil type (HPOO or LPOO) for eight weeks. At baseline and trial endpoint (8 weeks), data collection will include anthropometric measurements, dietary intake, biochemical indices, inflammatory and oxidative stress markers in blood samples, hormones, bioavailability of phenolic compounds, as well as lifestyle parameters i.e., health-related quality of life, physical activity levels, sleep quality. Ethical approval, informed consent, and data protection procedures will be strictly followed. Statistical analyses will be conducted using SPSS software (SPSS Inc, ΙΒΜ, Chicago, IL, USA). The study is anticipated to explore whether consumption of high-phenolic olive oil favorably modulates markers related to obesity and metabolic abnormalities, while also improving nutritional status and quality-of-life parameters.

High Phenolic Olive Oil for Enhancing Metabolic Health: a Randomized-controlled Trial in Patients With cEntral Obesity (HOPE)