Only 15% of people who consume fast food in New York City check the calorie information on the menus, according to a study published in British Medical Journal (BMJ).

Since 2008, New York law has enforced calorie information on menu boards in chain restaurants with 15 or more locations throughout the nation.

According to various studies, there is an association with the consumption of fast foods and high energy intake (and the likelihood of obesity).

Currently, 17 percent of children and 33 percent of adults are obese in United States. Moreover, the CDC reported that medical costs linked to obesity were approximately$147 billion in 2008. The researchers surveyed more than 8,000 people in 2009.

They carried out surveys 12 months before the regulation came into force and nine months after its implementation. The surveys took place at 168 locations selected randomly from the city's top 11 fast food chains.

15,798 customers, all of them adults, provided register receipts and answered some questions. The researchers gathered information from 7,309 people in 2007 and 8,489 in 2009.

The result showed average calorie-per-purchase decrease at three main chains: McDonald's had a 5.3 percent drop, Au Bon Pain a 14.4 percent reduction, and KFC had decreased 6.4 percent. Contrastingly, Subway's average energy content rose 17.8 percent. Subway actively promotes large portions.

"Calorie labeling will help consumers make an informed choice about what they eat, but sustained improvements in the nation's diet will require a transformation of the food supply too." said the Dr Susan Jebb from the MRC Human Nutrition Research Centre, Cambridge, England.

"But this study also illustrates the importance of how the restaurant or food chain acts. It is going to require a combination of factors to make a big difference," she added.