Dieters watch out! Food purchased from the shelves of your local supermarket might contain more calories than described on the packs. The same goes with popular restaurants also.

According to a study conducted on 10 chain restaurants, including Wendy's and Ruby Tuesday, it was concluded that there was an 18 per cent increase in the calories listed for various food products.

Tufts University researchers noticed that same findings in the research labs. That could be tipping the scale against you, say researchers in a University press release.

"Still if every time you eat out, you get a couple of hundred calories or more than you think, that can add up really easily," said lead researcher Susan Roberts, a professor of nutrition at Tufts University.

Reports stated that a majority of packed food products fell within the error margin of 20 per cent that is allowed by the Food and Drug Administration.

Findings stated that Wendy's Ultimate Chicken Grill had nine per cent more calories, McDonald's McChicken sandwich had three per cent ore calories, P. F. Chang's large Sichuan-style asparagus had more than double the 200 calories it was supposed to have.

Local and state officials will soon tell chain restaurants to post proper nutrition information about their food.