This is the protocol for a review and there is no abstract. The objectives are as follows:
To assess the effects of interventions that involve manipulation of and comparison of different sizes or sets of physical dimensions of a portion, package, individual unit or item of tableware on unregulated (ad libitum) selection or consumption of food, alcohol or tobacco products in adults and children.
To assess the extent to which the effects of such interventions may be modified by:
a) study-level characteristics, such as target product type (food, alcohol, tobacco) and whether the target of the manipulation is a portion, package, individual unit or item of tableware;
b) intervention characteristics, such as magnitude of the difference in size; and
c) participant characteristics, such as age, gender and socioeconomic status.