Tuccinardi D, et al. - In this cross-over, randomized, double-blind, placebo-controlled clinical trial, researchers evaluated how obese people are impacted by walnuts in terms of cardiometabolic outcomes and assessed underlying mechanisms using new methods, including metabolomic, lipidomic, glycomic and microbiome analysis, combined with lipid particle fractionation, appetite-regulating hormones, and hemodynamic measurements. The study sample consisted of 10 obese people. Study participants had two 5-day inpatient stays, during which they consumed a smoothie containing 48 grams of walnuts or a macronutrient-matched placebo smoothie without nuts; there was a washout period of 1 month between the two visits. These data give a more comprehensive mechanistic perspective of the effect on cardiometabolic variables of dietary walnut consumption. An early but significant decrease in ceramides and other atherogenic lipids was seen after consuming walnut via an analysis of lipidomic and lipid nuclear magnetic resonance spectroscopy. This could help explain the long-term advantages of walnuts or other nuts on insulin resistance, cardiovascular risk and mortality. They found no significant variations in hemodynamic or metabolomic analysis or in microbiome host health-promoting bacteria, like Faecalibacterium.