Santa Clara County Supervisor Liz Kniss must have forgotten that her constituents are known for their big brains. The Bay Area hosts Silicon Valley – a hub for engineers and venture capitalists. But a suggestion for a proposed ordinance being floated by Kniss assumes that the people who develop NASA technology are easily stumped by restaurant menus.

The legislation that the board of supervisors on Tuesday asked the county health department to develop – the latest quick-fix diet scheme proposed in the name of public health – assumes that consumers can’t tell the difference between french fries and fruit cups. Luckily, Governor Arnold Schwarzenegger showed a little more faith in Californians when he vetoed a statewide version of what’s being contemplated in Santa Clara County.

Kniss would like to require restaurants to turn their menus into encyclopedias, featuring long lists of nutritional warnings next to every item. For most of us, a back page of fat-and-calorie endnotes would suffice. But this proposal would force consumers to suffer through the informational equivalent of an ice-cream headache before ordering lunch.

Nutrition activists have already tried and failed at the knowledge-equals-behavior approach. In the early 1990s they pushed the government to mandate nutrition information on grocery items, but healthier eating habits didn’t follow. Most people who reported using “Nutrition Facts” to fill their shopping carts were the people who already considered themselves health-conscious. Proponents often cite studies based on focus groups or questionnaires. This data comes from asking individuals – in front of several other people – what items they would likely order from labeled and unlabeled menus. Not surprisingly, most publicly boast that they would certainly select the lowest-calorie food.

While people talk a big game in phone surveys and focus groups, few Americans change their eating behavior when faced with a nutritional profile of their food. In the real world, studies show that meal selection is primarily influenced by factors like smell, taste, texture, hunger, cravings, time and convenience – not diet facts.

Besides, Kniss’ proposal would only target restaurants with standardized menus and 15 or more locations. This excludes most of the county’s restaurants, including taco stands, sports arenas and white-tablecloth establishments. Also, on Sept. 11, 2007, a federal judge struck down New York’s version of menu labeling, ruling that it conflicted with federal authority.

When he vetoed the state bill in October, Schwarzenegger gave the state another reason to stop menu labeling proposals: They’re completely impractical. The governor heard complaints from the restaurant community, ranging from the heavy costs of testing the food and reprinting menus to the floodgate of lawsuits that would pour in from customers who ate two more carbs than the amount printed.

So why are Santa Clara County policy-makers ignoring this losing track record?

Love handles don’t distinguish between the calories from a butter-drenched lobster tail and those from fast-food fruit parfait. So if the intent of the legislation is truly to focus on people’s weight, it shouldn’t make a distinction either.

While anyone with an IQ above room temperature knows the difference between a bucket of fried chicken and a mixed green salad, most restaurants provide nutrition information anyway. Dieters and picky eaters can already find nutrition facts on posters, brochures, Web sites and 1-800 numbers.

There’s a huge difference between personal responsibility and dietary paternalism. Legislators and nutrition activists want to turn personal meals into public affairs, wedging legislation between you and your waistline. Under the new law, calorie counts for every item will be plastered across menus, whether you want them or not. And this will have unintended consequences.

A growing chorus of researchers is cautioning regulators about the collateral damage of programs similar to menu labeling. During the same time that health officials have placed increasing emphasis on obesity rates, the incidence of eating disorders has nearly tripled. As Senator Hillary Clinton put it, “many adolescents misinterpret (the fight against obesity) as a message that they should eat to achieve the body of a runway model. Anorexia and bulimia are increasingly common among our nation’s youth.”

Americans should still have a right to guilt-free eating.