Film fans should be given more information about how many calories they consume during a trip to the cinema, the Food Standards Agency (FSA) said today.

The nutrition watchdog is concerned about the portion sizes of cinema snacks which are often high in fat, sugar or salt.

"We recognise that trips to the cinema are occasional treats and food eaten there only represents a small amount of the nation's calories. However, the food on offer at cinemas is food that is often high in fat, sugar and salt," an FSA spokesman said.

"It is also served in pretty large portions and people don't have a choice to choose something smaller, for example the smallest soft drink on offer can be as big as a pint and pop corn tends to come in large buckets.

"The FSA thinks it's a good idea that people should have more choice. If they want to order a smaller pop corn box or soft drink then it should be available."

FSA chief executive Tim Smith told The Times cinema food was "a concern".

"There is a myth that popcorn is calorie-free but that is not the case," he said.

Mr Smith said there seemed to be increasingly large snacks on sale, adding: "Who would ever have thought of the idea of a family needing a wheelbarrow to go into a cinema?"

The Times said a large sweet popcorn from a central London cinema weighed 375g and was likely to contain around 1,800 calories.

The FSA is already working with food businesses to introduce calorie information for customers and said some restaurant businesses, including Wimpy and Pret a Manger, have already committed to doing that long term.

Mr Smith told The Times that a trial scheme had suggested people chose products with fewer calories when they were clearly marked.

"It seems where there is a choice between a chicken salad with 420 calories and one with 320 calories they are picking the lower one," he said.

The FSA spokesman added: "We are currently consulting on what a calorie labelling scheme should look like and will be publishing our final recommendations in the summer.

"We look forward to working with all food outlets to provide choice so that people can make healthier food choices."