To explore the extent to which appetite status influences portion size estimation in men under laboratory conditions and to quantify how much participants’ portion estimates differed from the recommended portion sizes defined by authoritative bodies (i.e. government and health professionals’ reference amounts).

Repeated, randomized cross-over trial with each participant attending the laboratory on four separate occasions. At each session, participants rated the number of portions of eight foods and beverages displayed in front of them. Participants rated portions twice after consuming breakfast (full conditions) and twice after an overnight fast (hungry conditions). Portion estimates were compared with reference amounts from the British and American Dietetic Associations, from the UK Food Standards Agency and from the US Food and Drug Administration.

Food skills laboratory, University of Chester, UK.

Twenty-seven non-obese men (mean age 24·9 (sd 6·5) years).

Portion size estimates for all items were significantly smaller under hungry than under full conditions (P < 0·01). Relative to reference instruments, estimates were significantly smaller for all foods except banana, irrespective of appetite status (P < 0·001).

In this data set, appetite status altered the perception of food amounts. There were large discrepancies between participants’ perception of a portion and recommendations from health professionals and government standards. Nutritional educational strategies should take into account the role of hunger along with a person's familiarity with existing portion size systems when advising on portion sizes.