Walnut consumption increases activation of the insula to highly desirable food cues: A randomized, double-blind, placebo-controlled, cross-over fMRI study


  • Funding information The project was supported by a Harvard Clinical and Translational Science Center Grant (UL1 RR025758) from the National Center for Research Resources and by an NIH grant (DK081913). The California Walnut Commission (CWC) supported the study through an Investigator-Initiated Study grant. The CWC approved funding for the study, but had no role in study design; conduct of the study; collection, management, analysis, and interpretation of the data; or preparation, review, and approval of the manuscript.
  • The authors Olivia M. Farr and Dario Tuccinardi contributed equally to this work.
  • Abbreviations: ADA, American Diabetes Association; ALA, alpha-linoleic acid; BMI, body mass index; BOLD, blood oxygenation level dependent; CNS, central nervous system; CRC, clinical research center; CVD, cardiovascular disease; fMRI, functional magnetic resonance; FWE, family-wise error; GLM, general linear modeling; MPRAGE, Magnetization Prepared Rapid Gradient Echo; NMDA, N-methyl-D-aspartate imaging; TR, repetition time; TE, echo time; VAS, visual analog scales.



The use of walnuts is recommended for obesity and type 2 diabetes, although the mechanisms through which walnuts may improve appetite control and/or glycaemic control remain largely unknown.

Materials and Methods

To determine whether short-term walnut consumption could alter the neural control of appetite using functional magnetic resonance imaging, we performed a randomized, placebo-controlled, double-blind, cross-over trial of 10 patients who received, while living in the controlled environment of a clinical research center, either walnuts or placebo (using a validated smoothie delivery system) for 5 days each, separated by a wash-out period of 1 month.


Walnut consumption decreased feelings of hunger and appetite, assessed using visual analog scales, and increased activation of the right insula to highly desirable food cues.


These findings suggest that walnut consumption may increase salience and cognitive control processing of highly desirable food cues, leading to the beneficial metabolic effects observed.