The fashion for large wine glasses has fueled a rise in the number of "invisible" calories people are inadvertently consuming through alcohol, the chair of the Royal Society for Public Health has warned.
Prof Fiona Sim said that the slow increase in the volume of glasses meant few people realised how much they had consumed, or were aware how calorific alcohol could be.
A 175ml glass of wine contains around 160 calories, the same as a slice of Madeira cake, but many bars and restaurants serve wine in 250ml glasses or even larger. It means that drinking just two large glasses of wine is more calorific than a portion of McDonald's fries and exceeds the recommended daily alcohol intake for women.
Prof Sim is calling for a new law which would force drinks companies and restaurants to include calorie counts on bottles and menus. Since 2011 all packaged food in the European Union has had to include nutritional information, including calorie counts, but alcohol above 1.2 per cent is exempt.
"Among adults who drink, an estimated 10 per cent of their daily calorie intake comes from alcohol," Prof Sim wrote in the British Medical Journal.
"With the insidious increase in the size of wine glasses in bars and restaurants in the past decade it seems likely that many of us have unwittingly increased the number of invisible calories we consume in alcohol.
"Information provided to consumers must be honest and useful. Alcohol content in units and calorie content in calories should be included on both drinks labels and menus.
"There are no reasons why calories in alcohol could be treated any differently from those in food."
Prof Sim is also calling for doctors to start asking patients about the calorie content from alcohol as well as food, to get a better picture of lifestyle. Calories from alcohol is rarely included in lifestyle and obesity assessments.
The European Union is considering whether to remove the exemption for alcohol and was due to report back in December, but has so far not ruled on the issue. A recent survey found that 80 per cent of the 2,117 adults questioned did not know the calorie content of common drinks, and most were completely unaware that alcohol contributed to the total calories that they consumed.
Most respondents were in favour of calorie labelling on alcoholic drinks.
The US Food and Drug Administration has mandated calorie labelling on alcoholic drinks from December 2015 in US restaurant chains with 20 or more outlets.
On this side of the Atlantic the Public Health (Alcohol) Bill 2015 will, if passed, make Ireland the first EU country to insist on calorie labelling on alcoholic drinks.