Personal and social norms for food portion sizes in lean and XXXX adults.

@entity1 @entity28
BACKGROUND: Portion size is an important component of dietary advice for weight control, but little is known about what portion sizes @entity1 consider 'normal'. This study determined the effect of body mass index (BMI), gender, dietary restraint and liking of the food on personal and social portion size norms for a range of foods and the degree of certainty over the norms. METHODS: Thirty lean (BMI 20-25   kg   m(-)(2)) and 30 @entity28 (BMI 30-35   kg   m(-)(2)) @entity1 and @entity1 (aged 18-60 years) viewed 17 different portion sizes of 12 foods on a computer screen on two occasions a week apart. @entity1 responded 'more' or 'less' to each photograph reflecting personal portion size preference or perceived portion sizes of others. Personal and social norms for portion sizes of each food were determined using the method of constant stimuli giving a sigmoidal curve of the probability of answering 'less' over a range of portion sizes. The slope of the sigmoid at the norm gave a measure of certainty about the norm. Regression models were used to examine the effect of BMI, gender, dietary restraint and liking of the food on personal norms, social norms, the relationship between norms, and the slopes. RESULTS: Personal norms were significantly larger in the @entity28 (P=0.026), @entity1 (P<0.001), those with lower dietary restraint (P<0.001), and those with higher liking for the food (P<0.001). Social norms were larger for @entity1 (P=0.012). The slopes at the norms were 30% shallower in the @entity28 and in @entity1 (P<0.001). CONCLUSION: Larger personal norms for portion size among the @entity28 , @entity1 , those with lower dietary restraint and those with higher liking for a food imply greater consumption, which may undermine weight control. Shallower slopes for norms in the @entity28 and in @entity1 may imply less clearly defined habitual portion sizes.
