Those who violate the new legislation will be fined, but restaurants using baked goods, prepared foods, and oils for deep-frying dough, have until next year to modify their recipes to eliminate trans fatty ingredients.

The health department says it will not issue fines, which range from $200 to $2,000 until October 1.

Restaurants are now also obliged to clearly display the amount of calories in their foods and some restaurant chains such as Burger King, McDonald's and Wendy's have already made the change to healthier oils and say most customers never noticed.

Trans fat increases the so-called bad cholesterol in food and clogs arteries and a diet high in trans fats can increase a person's risk for diabetes and heart disease.

New York city is the first in the U.S. to act on legislation to this degree and it is expected that more cities across the country will eventually adopt a similar plan.

Some New Yorkers however have said it is not the job of Mayor Michael Bloomberg, who proposed the plan last year, to decide what they eat.

Dr. Dansinger says weight loss drugs too are similarly ineffective in the long run, which is disappointing but he says even a small, temporary weight loss can benefit health and delay the onset of diabetes.

Programs that made people eat fewer calories worked better, along with those that involved more frequent visits to either diet groups or to a counselor's office.

The only commercial program included in the study was Weight Watchers and no studies that involved commercially prepared food or shakes were included because they did not include a non-dieting group for comparison.

Dansinger says the results were essentially the same, around a 6 percent weight loss after one year but that weight loss gradually disappears and almost all the weight was back on within five years, similar to what has been found with weight loss medications.

Dansinger says though some of the studies included exercise, his analysis was not designed to tell whether exercise helped weight loss last longer.

The research is published in the Annals of Internal Medicine.