Central adiposity, visceral fat, intra-abdominal fat, or a bigbelly, they all mean the same thing: increased risk of insulinresistance, cardiovascular disease, and type 2 diabetes.
Recently, astudy of the abdominal fat of 196 people demonstrated that suchvisceral fat produces something called retinol (vitamin A)-bindingprotein 4 (RBP4), a carrier protein that transports vitamin A aroundyour body. There was sixty times more RBP4 gene activity in thebelly fat of obese people than in the belly fat of lean people, andtwice as much in people with impaired glucose tolerance or type 2diabetes as in people with normal blood glucose.
The amount of RBP4 in the blood accurately reflected the amount offat around the central organs. In obese people, the blood level ofRBP4 was double or triple that of normal-weight people. RBP4 in theblood also correlated inversely with insulin sensitivity andinversely with gene activity of GLUT4, an importantinsulin-regulated glucose transporter.
The study authors noted that because of its close correlation withcentral fat levels, RBP4 could perhaps be used as a marker topredict risk of disease. Previous research has indicated that bloodRBP4 can be reduced by exercise and that RBP4 levels drop inassociation with improved insulin sensitivity.
In another study,teens who ate low carb diets and exercised also lowered their RBP4levels. In mouse experiments, RBP4 has been found to decrease theinsulin sensitivity of muscle and liver tissue.
Sources: Cell Metabolism, July 2007