Researchers at Iowa State and Cornell universities say sticking to a general rule of pouring just half a glass of wine regardless of age, size or gender could prevent overdoing it.
In the study, researchers worked with 74 undergraduate students and staff and asked them to pour white and red wine from bottles of varying fullness in a variety of settings into glasses with various shapes and sizes.
They had been selected on the basis that they consumed at least one glass of wine per week and they were questioned in advance of the study as to whether or not they poured by a particular rule, such as a half-glass rule or a "two-fingers below the brim" rule.
Regardless of size or gender, those who stuck to a rule poured less.
"About 70 percent of the people in the sample used the half-glass rule, and they poured significantly less by about 20 percent," says Laura Smarandescu, lead author and an assistant professor of marketing at Iowa State.
The researchers also looked at a variety of factors that came into play when subjects served themselves wine and found that men with higher body mass index (BMI) poured themselves more, although this was not the case for women with higher BMI.
Men who did not use a rule of thumb poured 31 percent more than those who did if they were considered overweight or obese and 26 percent more if they were at the midpoint of the normal BMI range.
For women, BMI itself did not seem to affect the amount of wine they poured, but women at the mid-point of their respective BMI scale poured 27 percent less under the half-glass rule compared with those who didn't follow the rule.
Researchers had expected to see men serving themselves in greater quantities, but were surprised to see the rule affected everyone equally.
While the study looked at pours, not consumption, researchers point to previous studies that show serving size is linked with overeating and so the same rule may apply to drinking.
"It is essential for all drinkers, especially men of higher BMIs, to have a rule of thumb for self-serving, because eye-balling a serving size is a difficult task and will often lead people to pour too much," says Dr. Brian Wansink, professor of marketing and director of the Cornell Food and Brand Lab. "Next time you open a bottle, serve yourself a half glass - regardless of the size of your glass - and you will be less likely to accidentally drink too much."
The study is to be published in an upcoming issue of the International Journal of Drug Policy.