Increased portion size leads to a sustained increase in energy intake over 4 d in normal-weight and overweight men and women

Large food portions may be facilitating excess energy intake (EI) and adiposity among adults. The present study aimed to assess the extent to which EI and amounts of foods consumed are influenced by the availability of different-sized food portions. A randomised within-subject cross-over, fully residential design was used, where forty-three (twenty-one men and twenty-two women) normal-weight and overweight adults were randomly allocated to two separate 4d periods where they were presented with either ‘standard’ or ‘large’ food portions of the same foods and beverages. The main outcome measures were the amount of food (g) and EI (MJ) consumed throughout each study period. Mean EI over 4d was significantly higher on the large portion condition compared with the standard condition in the total group (59·1 (SD 6·6) v. 52·2 (SD 14·3) MJ; P¼0·020); men and women increased their EI by 17% (10 (SD 6·5) MJ; P,0·001) and 10% (4 (SD 6·5) MJ; P¼0·005) respectively when served the large food portions relative to the standard food portions. The increased intakes were sustained over the 4d in the large portion condition with little evidence of down-regulation of EI and food intake being made by subjects. Increased food portion size resulted in significant and sustained increases in EI in men and women over 4d under fully residential conditions. The availability and consumption of larger portions of food may be a significant factor contributing to excess EI and adiposity. Appetite: Energy intake: Obesity: Portion size: Weight management: Adults The burgeoning rates of obesity in genetically stable populations such as in Europe and North America suggest that an increasingly obesogenic environment is the major driving force behind this epidemic (1) . Fostering the delicate balance between energy intake (EI) and energy expenditure to maintain a healthy body weight is now exceedingly difficult for many individuals. In the past few decades several key environmental and cultural factors have converged to increase the probability of over-eating in the face of reduced energy needs.