Researchers from Iowa State and Cornell University found that BMI affected how much men poured, but had no influence on women. However, people who used a "rule of thumb," such as a half-glass rule or a two-fingers-from-the-top rule when pouring wine, poured less regardless of BMI or gender.
Laura Smarandescu, an assistant professor of marketing at Iowa State, said that about 70% of the people in the sample used the half-glass rule, and they poured significantly less by about 20%.
Men with a higher BMI, who did not use a rule of thumb, poured more 31% more for men considered overweight or obese and 26% more for men at the midpoint of the normal BMI range. While BMI did not affect how much women poured, those at the midpoint of the normal BMI poured 27% less when using the half-glass rule than those who did not.
The study looked only at pours, not consumption. However, researchers pointed to previous studies that show serving size was linked with overeating. Free pouring wine increases the tendency to over consume because it was not as easily measured as other types of beer or spirits.
The study will be published in the International Journal of Drug Policy.