BMJ Open Diab Res Care 3:e000115 doi:10.1136/bmjdrc-2015-000115
  • Obesity studies

Walnut ingestion in adults at risk for diabetes: effects on body composition, diet quality, and cardiac risk measures

Open AccessPress Release
  1. David L Katz1,2
  1. 1Yale University Prevention Research Center, Derby, Connecticut, USA
  2. 2Griffin Hospital—Derby, Derby, Connecticut, USA
  1. Correspondence to Dr David L Katz; davkatz7{at}
  • Received 11 May 2015
  • Revised 18 August 2015
  • Accepted 28 August 2015
  • Published 23 November 2015


Background Despite their energy density, walnuts can be included in the diet without adverse effects on weight or body composition. The effect of habitual walnut intake on total calorie intake is not well studied. Effects on overall diet quality have not been reported.

Methods Randomized, controlled, modified Latin square parallel design study with 2 treatment arms. The 112 participants were randomly assigned to a diet with or without dietary counseling to adjust calorie intake. Within each treatment arm, participants were further randomized to 1 of the 2 possible sequence permutations to receive a walnut-included diet with 56 g (providing 366 kcal) of walnuts per day and a walnut-excluded diet. Participants were assessed for diet quality, body composition, and cardiac risk measures.

Results When compared with a walnut-excluded diet, a walnut-included diet for 6 months, with or without dietary counseling to adjust caloric intake, significantly improved diet quality as measured by the Healthy Eating Index 2010 (9.14±17.71 vs 0.40±15.13; p=0.02 and 7.02±15.89 vs -5.92±21.84; p=0.001, respectively). Endothelial function, total and low-density lipoprotein (LDL) cholesterol improved significantly from baseline in the walnut-included diet. Body mass index, percent body fat, visceral fat, fasting glucose, glycated hemoglobin, and blood pressure did not change significantly.

Conclusions The inclusion of walnuts in an ad libitum diet for 6 months, with or without dietary counseling to adjust calorie intake, significantly improved diet quality, endothelial function, total and LDL cholesterol, but had no effects on anthropometric measures, blood glucose level, and blood pressure.

Trial registration number: NCT02330848

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