Super-chef Jamie Oliver is back to film another season of his show "Food Revolution." This time he’s targeting school cafeterias in Los Angeles, a city usually inviting to camera crews. But Angelenos are making an exception in Oliver’s case, saying thanks but no thanks:

“I can’t get my foot into a single school. Which is a bit of a shame really,” he said by telephone Tuesday. “It just doesn’t seem in the interest of the public really. It’s not a great start for me, to be honest.”

Why on earth aren't the good people of Los Angeles interested in being portrayed as fatties on national television?

An L.A. Unified spokesman Monday said there is no chance for a change of heart.

“Reality TV has a formula. You either have to have drama or create conflict to be successful. We’re not interested in either,” Robert Alaniz said in an e-mail.

All “good” reality TV shows, including Oliver’s, have to follow conventional narratives to get ratings. There must be a dire problem, conflict has to occur, success has to be in doubt but ultimately achieved, the good guy must win. But real life doesn't always work like that.

Oliver himself discovered this when he returned to Huntington, WV, where his first season was filmed. Specifically, he found that children hated their new cafeteria food. Many were bringing lunches from home that were just as unhealthy as the original school menu.

Obesity not only defies the conventions of reality television, but it's also far more complex. Feeding children carrots instead of chicken fingers may sound great, but it doesn't even come close to addressing the full problem. Many factors contribute to obesity, from calorie counts to exercise to sleep. Researchers are coming up with smart new anti-obesity measures every day. One study found that breaks for physical activity during the school day prevents obesity and helps students concentrate. Cornell University research showed that subtle cafeteria changes, like putting the salad bar next to the cash register, helps students eat substantially healthier. Other research found that giving healthy cafeteria foods an attractive name, like "x-ray vision carrots," greatly increased consumption.

The problem is that none of these ideas will get the kind of ratings that starting a televised "food revolution" might. Other than PBS, we can’t imagine any network picking up a show that stars Ivy League academics pushing salad bars around cafeterias. But these subtle changes do far more to curb obesity than even the most earnest English chefs.