Visceral Reaction: Abdominal Fat Trumps BMI

From Heartwire
by Steve Stiles

July 14, 2009 (Quebec, Quebec City) — Two years ago, a group reported an inverse relationship between cardiorespiratory fitness and intra-abdominal adiposity that was independent of body-mass index (BMI) in patients with asymptomatic diabetes enrolled in the Quebec Family Study.

Now that research team, studying nondiabetics from the same observational study, has observed that poor fitness in overweight and obese people, compared with those with good cardiorespiratory fitness, is associated with low-grade inflammation. That's not necessarily a new finding, but another was more novel: "Our results show for the first time that the relation between obesity and inflammation is attributable to a very large extent to visceral adipose-tissue accumulation rather than to excess body weight per se," write Benoit J Arsenault (Université Laval, Quebec, QC) and colleagues in the July 15, 2009 issue of the American Journal of Cardiology.

A cohort of 272 asymptomatic men and women were scored for inflammation based on plasma biomarker levels. Visceral adipose tissue, measured by computed tomography (CT), was positively associated with levels of C-reactive protein (CRP) and interleukin-6 (p<0.0001) but inversely associated with adiponectin levels (p<0.0003) after adjustment for fitness levels (as measured by bicycle ergometry).

Inflammation scores went up (p<0.05) with greater insulin resistance, and they were reduced (p<0.05) in subjects with low vs high levels of visceral adiposity (low defined as <130 cm2 for men and <100 cm2 for women). Within both subgroups with low and high levels of visceral adiposity, subjects with high and low fitness had similar inflammation scores.

Visceral adiposity levels varied widely at any given BMI value.

"The state of insulin resistance associated with visceral adiposity appeared to represent a potential link between low [cardiorespiratory fitness] levels and low-grade inflammation. Hence, we propose that unfit subjects are characterized by an inflammatory state because of their increased visceral [adipose-tissue] accumulation and associated insulin-resistance state."