Did you hear about renowned Harvard scientist Barbara Kahn's latest published research? I blogged about it recently. Kahn and colleagues state, in a report published in Cell Metabolism (July 2007), that it's possible to use a simple blood test to detect the presence of a specific protein called RBP4. Kahn et al say the presence of RBP4 can be used to measure accumulations of deep belly fat. Underpinning this research is a belief that such accumulations of belly fat increase risk for metabolic syndrome, leading to various maladies including heart disease and diabetes.

However, not everyone accepts this point of view. A Yale research team says that deep belly fat may not be so evil after all. The researchers, who are based at Yale University School of Medicine in Chevy Chase, Maryland, assert that metabolic syndrome is caused not by belly fat but by insulin resistance in skeletal muscle. This resistance, they state, makes it tough for the body to manufacture glycogen, so - in people who are insulin resistant - energy that cannot be stored as glycogen gets diverted into fatty acid production, which then contributes to metabolic syndrome.

The team compared abdominal fat levels in young and healthy individuals, some of whom were insulin sensitive and some of whom were insulin resistant. The result? "There is absolutely no difference in the volume of abdominal fat," states Yale's Gerald I. Shulman, who was lead author of the study. Abdominal fat, says Dr. Shulman, "may come later in the course of the disease [metabolic syndrome], but it's not a primary, underlying factor."

It used to be that fat was just fat. Not anymore. Turns out that even fat is, upon close examination, more complicated than we ever realized. Did you know, for instance, that accumulations of deep belly fat are particularly harmful? Such accumulations are a risk factor for Type 2 diabetes because they are associated with increased insulin resistance, not to mention increased risk of heart attack.

One problem with deep belly fat, however, is that you can't necessarily detect it with a tape measure or by eyeballing someone's waistline. That is, you can't tell by just looking at a person how much of the fat surrounding their abdomen is deep belly fat versus the subcutaneous fat that lies just under the skin's surface. However, a new study reports that a simple blood test could solve this problem by measuring quantities of the retinol-binding protein 4, also known as RBP4, in the bloodstream. RBP4 is present in much higher levels in the bodies of those with greater amounts of deep belly fat. Not only does this mean that testing for high levels of RBP4 could be useful in assessing risk for conditions such as Type 2 diabetes or heart disease, it also opens up the possibility of treating such conditions by somehow manipulating RBP4 levels.

The study in question was conducted by scientist Barbara Kahn and colleagues from Harvard Medical School, Beth Israel Deaconess Medical Center, and the University of Leipzig, Germany. The results have been published in the journal Cell Metabolism (July, 2007). Kahn is particularly well known in the area of diabetes-related research for her work on insulin resistance in mice.