The effect of diets enriched with high-oleic sources on anthropometric, inflammatory, and blood pressure outcomes: a systematic review and meta-analysis

High-oleic diets (HODs) have been proposed to improve obesity-related and inflammatory outcomes, yet randomized evidence remains inconsistent. This systematic review and meta-analysis evaluated the effects of HODs compared with low-oleic diets (LODs) on anthropometric, inflammatory, and blood pressure indices. Randomized controlled trials assessing HODs versus LODs in adults were systematically identified. Most included interventions were designed to be eucaloric, aiming to maintain body weight and isolate the effects of fatty acid composition. Weighted mean differences (WMDs) with 95% confidence intervals (CIs) were pooled using random-effects models. A total of 20 RCTs with 1009 participants published between 1991 and 2023 were included. HODs did not significantly affect body weight (WMD: − 0.11 kg; 95% CI: − 0.42 to 0.19), BMI (WMD: − 0.27 kg/m 2 ; 95% CI: − 0.64 to 0.09), total body fat (WMD: − 0.13%; 95% CI: − 0.81 to 0.56), leptin, CRP, or cytokines (IL-6, TNF-α, IL-2, IL-10). Blood pressure indices similarly remained unchanged. In contrast, a small but statistically significant increase in waist circumference (WC) was observed (WMD: 0.63 cm; 95% CI: 0.01 to 1.26), a finding replicated across subgroups with BMI > 25 kg/m 2 , intervention duration ≤ 4 weeks, and ≥ 80% oleic-acid intake. Meta-regression showed no linear associations between oleic-acid proportion or duration and primary outcomes. Heterogeneity was consistently low. HODs appear metabolically neutral regarding weight, BMI, adiposity, systemic inflammation, and blood pressure, but may be associated with a very small increase in WC in certain subgroups, although the clinical relevance of this finding is likely minimal and may reflect short-term transient changes rather than meaningful adiposity gain. While the clinical significance of the observed WC increase is likely minimal, longer, larger trials are needed to clarify long-term effects on central adiposity and inflammatory processes.