Diners may drink less wine if they are given a smaller glass, a new study suggests.
Researchers found that people who eat out in restaurants drink less when they are given a 300ml wine glass compared with a 370ml one.
But the same effect was not noticed in bars where people consumed the same amount regardless of glass size.
The authors suggested that the effect might be more noticeable in restaurants as people are more likely to buy wine by the bottle or carafe, whereas in bars more wine is purchased by the glass.
The authors, from the University of Cambridge, analysed data on eight studies concerning glass size and the amount people drink.
Five bars and restaurants in England participated in the studies between 2015 and 2018.
In restaurants, when glass size was increased to 370ml, wine sales increased by 7.3%.
They also noted that using 250ml glasses led to reduced sales but this finding was not deemed statistically significant.
The authors commented that wine glasses have increased in size almost seven-fold over the last 300 years with the most marked increase being a doubling in size since 1990.
During this time, the amount of wine consumed in England quadrupled, although the number of wine consumers stayed constant.
“Pouring wine from a bottle or a carafe, as happens for most wine sold in restaurants, allows people to pour more than a standard serving size, and this effect may increase with the size of the glass and the bottle,” explained first author Dr Mark Pilling.
“If these larger portions are still perceived to be ‘a glass’, then we would expect people to buy and consume more wine with larger glasses.
“As glass sizes of 300ml and 350ml are commonly used in restaurants and bars, drinkers may not have noticed the difference and still assumed they were pouring a standard serving. When smaller glass sizes of 250ml are available, they may also appear similar to 300ml glasses but result in a smaller amount of wine being poured.
“In contrast, very large glasses, such as the 450ml glasses, are more obviously larger, so drinkers may have taken conscious measures to reduce how much they drink, such as drinking more slowly or pouring with greater caution.”