Following an application from Kao Corporation, submitted pursuant to Article 13(5) of Regulation (EC) No 1924/2006 via the Competent Authority of the United Kingdom, the Panel on Dietetic Products, Nutrition and Allergies was asked to deliver an opinion on the scientific substantiation of a health claim related to diacylglycerol oil and reduction of body weight. The food constituent, diacylglycerol (DAG) oil, and the food constituents, vegetable oils of similar fatty acid composition containing mostly (>90%) triacylglycerol (TAG), which DAG oil should replace in order to obtain the claimed effect, are sufficiently characterised in relation to the claimed effect. Weight loss is a beneficial physiological effect for overweight subjects. Seven randomised controlled trials (RCTs) were identified by the applicant as being pertinent to the claim. One RCT which had major methodological limitations did not allow conclusions to be drawn for the scientific substantiation of the claim. The results from six RCTs with respect to the effect of DAG oil (as a replacement of TAG oils) on body weight are inconsistent and apparently unrelated to the DAG dose, study size or study duration, and the evidence provided in support of mechanisms by which DAG oil could exert the claimed effect in humans under the proposed conditions of use is not convincing. One unpublished meta-analysis on the effects of DAG oil (as compared to TAG oils) on body weight in humans which included data from all these RCTs was also provided. The meta-analysis had a number of potential sources of bias and did not provide additional information for the scientific substantiation of the claim. The Panel concludes that a cause and effect relationship has not been established between the consumption of DAG oil (as a replacement of TAG oils) and a reduction in body weight. © European Food Safety Authority, 2011