Controlled human intervention trials are required to confirm the hypothesis that dietary fat quality may influence insulin action. The aim was to develop a food-exchange model, suitable for use in free-living volunteers, to investigate the effects of four experimental diets distinct in fat quantity and quality: high SFA (HSFA); high MUFA (HMUFA) and two low-fat (LF) diets, one supplemented with 1·24 g EPA and DHA/d (LF
n-3). A theoretical food-exchange model was developed. The average quantity of exchangeable fat was calculated as the sum of fat provided by added fats (spreads and oils), milk, cheese, biscuits, cakes, buns and pastries using data from the National Diet and Nutrition Survey of UK adults. Most of the exchangeable fat was replaced by specifically designed study foods. Also critical to the model was the use of carbohydrate exchanges to ensure the diets were isoenergetic. Volunteers from eight centres across Europe completed the dietary intervention. Results indicated that compositional targets were largely achieved with significant differences in fat quantity between the high-fat diets (39·9 ( sem0·6) and 38·9 ( sem0·51) percentage energy (%E) from fat for the HSFA and HMUFA diets respectively) and the low-fat diets (29·6 ( sem0·6) and 29·1 ( sem0·5) %E from fat for the LF and LF n-3 diets respectively) and fat quality (17·5 ( sem0·3) and 10·4 ( sem0·2) %E from SFA and 12·7 ( sem0·3) and 18·7 ( sem0·4) %E MUFA for the HSFA and HMUFA diets respectively). In conclusion, a robust, flexible food-exchange model was developed and implemented successfully in the LIPGENE dietary intervention trial.