The latest annual “F as in Fat” report from the Trust for America’s Health (TFAH) rehashed the same half-truths about Americans getting fatter that the group trotted out in 2005. Unfortunately for them, we have the half they left out.

The core flaw of TFAH’s report hasn’t changed in the three years that they’ve been publishing it: It relies on the dubious Body Mass Index (BMI) as a reliable indicator of health. This is the same measure that calls President Bush “overweight” and Governor Schwarzenegger “obese,” but it gets worse.

Writing in the International Journal of Obesity, Dr. David Cundiff suggested “abandoning the use of the BMI as a surrogate for physical inactivity and poor diet.” Similarly, Dr. Maria Franzosi wrote in The Lancet that “BMI can definitely be left aside as a clinical and epidemiological measure of cardiovascular risk.” Furthermore, this month the British medical journal The Lancet published a review of 40 obesity studies which found that “overweight” (as designated by the BMI) is in fact the healthiest weight category, healthier than “normal” or “obese” weights.

While it’d be premature to draw a sweeping conclusion here, the one intriguing thing that TFAH’s report may have to offer is the significant disparities in obesity rates in different states. It would seem to cast doubt on the activist hypothesis that “corporate food” is to blame for obesity in America, since places like Safeway and McDonald’s are distributed pretty evenly all throughout the country, but obesity isn’t. Could it be possible that differing rates of physical activity in these states leads to differing rates of obesity?