As San Francisco County Supervisor Eric Mar is quickly discovering, hell hath no fury like the Hamburglar. A cadre of McDonald’s corporate executives flew in from Chicago early this week to oppose Mar’s latest bill to bar fast food restaurants from serving up toys along with high-calorie kids’ meals.

The restaurant’s representatives noted that under the bill even a revised Happy Meal — hold the fries and sodas and add apples and milk — would have to be served without a toy. The measure, they said, could create an “unrealistic standard.”

No matter, Mar said, Happy Meals encourage unhealthy habits.

For the most part, Mission parents agreed.

“Not all parents can control our kids. We need help,” said one mother as she watched her three-year-old son Kenneth enjoy his favorite “un hamburgesa” while they waited for his father to get off work at a fruit stand nearby.

In any language, the hamburger contains 250 calories and 520 mg of sodium, according to the company’s own nutrition tables. And no, it would not pass muster for a toy-friendly food item in the original version of Mar’s legislation.

Low-income consumers, as many argued on Monday, make especially easy targets for fast food because many are looking for quick, cheap meals. It is perhaps why there are more fast food establishments here than elsewhere: 6.9 fast per square mile, versus 4.7 citywide, according to the Healthy Development Measurement Tool created by the Public Health Department.

And while San Francisco’s children are healthier than most in California, children living in San Francisco’s poor neighborhoods are, on average, less fit.

San Francisco children had, by far, the lowest fast food consumption of all counties statewide in a 2007 study — 61.2 percent of the children and teens surveyed had not eaten a fast food meal within a week’s time, compared to 27.8 percent statewide.

Cara and her mother stopped in for a snack at the 24th & Valencia McDonald's. "She loves her fries," said Mom. "And I was hungry, too."

The study, known as the California Health Interview Survey, was conducted by researchers at the University of California, Los Angeles.

Only 3.9 percent of the city’s children were considered overweight for their age, far from the 11 percent for the rest of California.

That survey, however, dug no deeper than the county level. The Department of Education’s fitness test offers a closer look. San Francisco’s fifth- and seventh-graders scored on par or better than the statewide averages in areas like aerobic fitness on the 2008-2009 California Physical Fitness Test.

However, only 35 percent of the fifth-graders in the Mission’s five elementary schools, for example, met five of six “health fitness zone” requirements on the Physical Fitness Test, compared to 50 percent citywide.

The Mission’s middle school students were behind their citywide peers in aerobic fitness by as much as 30 percent last year.

Parents at the Mission McDonald’s agreed that linking toys to healthy food would make a difference. “Sometimes we are passing by here and she just looks for the toys,” said Vanessa, who was having lunch with her daughter Malesca at the 24th & Mission location.

Vanessa acknowledged that while she and her daughter Malesca don’t come to McDonald’s very often, “every time we come I get her the Chicken McNuggets.” The latter contain 190 calories and 12 grams of fat in a four-piece, 2.3-ounce serving.

Asked by her mother whether she’d prefer a salad with a toy or the nuggets without, she replied, “Salad with a toy.”

“It’s always because of the toys, only the toys” chimed in another parent. “If he notices the food is healthy, he would still choose the toy. The toy will always be more important for the kid.”

The Mar bill, which called obesity “a public health problem of epidemic proportions,” cited study after study that suggests Bay Area kids are out of shape.

“Combining unhealthy food with a toy reward undermines the efforts of educators to teach children healthier eating habits,” said Eileen Woods, a teacher at Hillwood Academy Day School in Pacific Heights.

Scott Rodrick, who owns 10 of San Francisco’s 19 McDonald’s restaurants, said the measure would pose an “operational nightmare” for his businesses, and that as a parent he opposed the “government trying to tell us how to raise our kids.”

Some Mission parents agreed.

“I think sometimes that people go overboard,” said Smitha, as daughter Cara munched on some french fries in her stroller. “Maybe it would be better if there is a healthy option, but you could choose to give your child junk, because you can’t legislate everything.”

Smitha glanced down at Cara and shrugged, “She likes her fries. I might say right now that I don’t want to give her McDonald’s Happy Meals, but when you’ve got a screaming kid, at least twice out of five or ten times, you’re gonna give them the happy meal.”