A similar law will take effect in New Jersey next year, and dozens of such bills are pending around the country, including in Harrisburg.
What's different in Philadelphia will become apparent on April 1, when restaurants with individual menus must list saturated fats, trans fats, carbohydrates, and sodium, in addition to calories, with every item.
No one really knows what will come of this broader experiment in attempted behavioral change.
"The majority of people, I believe, will see this as cumbersome and an overreaction and not necessary," said George McKerrow Jr., president and chief executive officer of Ted's Montana Grill, who anticipates having to expand the menu at his South Broad Street location from two pages to six.
Still, just two months after Ted's added calories alone to its menu here, responding to a New York City requirement, McKerrow has noticed a small but measurable change in Philadelphia: "Some people have chosen to eat the healthier items more often."
Restaurants initially fought all efforts to mandate labels on menus. As the movement spread, with dozens of variations proposed across the country, the industry switched its goal to uniformity: calories, yes; sodium, no.
It has won that fight everywhere except Philadelphia. City Council approved the measure in 2008, after viewing data that showed the impact of chronic diseases related to diet - diabetes is diagnosed in 13 percent of residents, high blood pressure in 36 percent - broken down by district.
Diabetics must manage their intake of carbohydrates (including sugar); too much sodium can raise blood pressure. Both are listed on the familiar nutrition-facts label on all prepackaged goods.
"But it is really hard for people, if they eat out, to know about the sodium content," city Health Commissioner Donald Schwarz said.
