Thursday, July 20, 2006

Does BMI really count for all?

This is the kind of report that you want to say "of course I pretty much figured this" - this is something intuitive.

For years doctors have used the body mass index (BMI), a ratio of height and weight, to characterize the clinical weight status of their patients. The lower the number, the presumption goes, the leaner the person, and anyone with a BMI above 30 is characterized as obese and at high risk for the associated complications.

But the BMI has come under scrutiny lately, and other techniques that measure how the weight is distributed on the body are thought to provide a better way to assess risk. Now a study in mice by scientists at The Jackson Laboratory indicates that the usefulness of the BMI is suspect even at the genetic level.

In research published in PLoS Genetics, researchers used a combination of computational, molecular, and genetic tools to identify locations on the mouse genome that influence adiposity (amount of body fat), overall body size and bone structure. Applying an analytical technique called "structural equation modeling" to the genetic and physical characteristics of mouse inbred crosses, the scientists went beyond the one-gene, one-trait approach to reveal the networks of effects created by the influence of multiple genes.

The scientists say they found strong evidence that a high weight is not necessarily directly associated with a high percentage of fat.

At the clinical level, the research suggests that more refined measurements are needed to distinguish individuals with a large body mass from those who are truly obese.