Officials in New York are trying to cut obesity in the city by forcing restaurants to list the calories in each dish or serving.
By Sima Kotecha
Newsbeat US reporter
Every restaurant and takeaway with more than 15 branches will have to comply by June or face a hefty fine.
Some chains have already started doing it, like Starbucks.
Our straw poll in one of their coffee shops showed that when it comes to losing weight, many people don't realise how many calories they're consuming.
One person guessed that a slice of banana coffee cake topped with pecans contained around 200 calories. In fact it's 480.
One customer said: "We have no idea what we're eating but now we will. It'll make me go for the healthier option."
Officials hope listing the calories in food will fight the city's flabby image.
More than half of New Yorkers are clinically overweight.
Officials in the city want to stop 130,000 people from becoming obese and another 30,000 from developing diabetes within the next five years.
In turn, that could cut rising medical bills for treating these and other associated weight disorders.
Health department spokeswoman Jessica Scaperotti said: "We just want people to have the information available to them to make healthful decisions."
Not everyone agrees
Restaurant association spokesman Chuck Hunt says he doesn't object to a voluntary agreement.
Starbucks already lists the calories in all of its products
He said: "Our problem was the government agency forcing them to do it.
"We think restaurants should be able to determine from their customers how they want to get the information."
Matilda is 28 and weighs 14.5 and a half stone.
She told Newsbeat: "I don't care about the amount of calories. If I want it, I'll eat it."
One of the fast food chains affected by the ruling is McDonalds.
Some staff there are worried too.
They are concerned that if people realised that a cheeseburger was 320 calories they might go elsewhere and they'd lose business.
Subway takeaway restaurants started listing calories in 2007
Sit down chains like T.G.I. Friday's are also having to come into line.
Artery-clogging trans-fats are already banned in New York.
They are made when food processors harden fat to make it more like butter and can be used for frying or baking or put into processed foods and ready-made mixes for cakes and drinks like hot chocolate.
Smoking was banned in New York's restaurants and bars in 2003.
Lawmakers in California and Washington state are now considering fat-busting legislation to encourage people to eat more healthily.