Yesterday we detailed some of the heavy-handed cause célèbres of the anti-soda crusader Thomas Frieden. Today, ABC News details yet another intrusive proposal that some anti-fat fanatics are drumming up support for: body mass index (BMI) surveillance.

On its surface, this proposal has many flaws. BMI is, at best, an oversimplified way to classify weight. Consider that under the BMI system, Tom Cruise is officially “overweight” and Arnold Schwarzenegger is officially “obese.” And the British National Health Service recently labeled an athletic 5-year-old girl “overweight” using BMI.

Such ridiculous claims arise because BMI doesn’t take into account whether mass is due to muscle or fat. It’s no surprise, then, that some doctors have called for abandoning the use of BMI altogether.

This kind of monitoring has been tried in enough places for people to know that it has unintended consequences. Arkansas, for example, implemented a “BMI screening” law in 2003 requiring schools to track kids’ masses and send a report card to parents. Reviewing the effectiveness of its implementation in 2006, The Baltimore Sun reported on its utter failure:

Parents in Arkansas did not take kindly to the fat measurements. In fact, last year state lawmakers tried to have the law repealed. According to the Arkansas Democrat-Gazette, during the first year of the screenings 13 percent of parents said their children had been teased at school because of the program.

But did it help reduce the number of overweight kids? Nope. It did, however, highlight the idea that weight is all-important, which could lead to unhealthy eating behaviors like bulimia and anorexia.

And the extra stigma on weight isn’t even necessarily, well…healthy. One study last year in the journal Obesity tracked 11,000 people ages 25 and older and discovered that those who were overweight and obese (but not extremely obese) were at a far lower risk of dying than those of normal weight.

The case for a federal BMI surveillance program just doesn’t make sense. Is there a nationwide mirror shortage we’re not aware of?