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It has been shown that obesity
is associated with worsening kidney function in terms of renal hyperfiltration,
hyperperfusion, as well as microalbuminuria. Central obesity (also known as
central body fat) is well known as a risk factor for insulin resistance and type
2 diabetes. Several reports have associated central body fat with lower
cardiopulmonary function and overall physical fitness. However, the deleterious
effect of central body fat on renal function has been primarily attributed to
other existing co-morbidities (e.g. diabetes, hypertention and
hypercholesterolemia).
On April 11, 2013, Kwakernaaket al published a paper in the Journal of American Soceity of Nephrology(JASN) on whether body fat distribution, as measured by the
waist/hip ratio (WHR), is associated with renal hemodynamics, independent of BMI,
in a cross-sectional analysis of 315 healthy normotensive persons with normal
fasting glucose levels.
The main finding of this
study is that in the healthy population, independent from BMI, higher WHR was inversely
associated with glomerular filtration rate and effective renal plasma flow, and
positively associated with filtration fraction. These findings were consistent
in both univariate and multivariate analyses.
The study was a cross-sectional analysis and thus no causal inference can be drawn.
Additionally, WHR is not an accurate measure of central body fat, which
involves several types of visceral fat. Rather, central body fat is best quantified by advanced
imaging modalities e.g. DEXA, CT or MRI.
Nevertheless, the findings from this
study support conclusions the PREVEND study that was
published in the American Journal of Kidney Disease in 2003, also from the
Netherlands. PREVEND provided evidence to support central body fat as a a risk factor for diminished kidney function.
The bottom-line is that increasing
evidence now supports the conclusion that weight loss and increased physical
activity are renoprotective even among healthy individuals.
Dr. Youssef MK Farag
Dr. Farag is a
research fellow in the renal division at Brigham and Women’s Hospital, a
teaching affiliate of Harvard Medical School. He is currently pursuing a master
in public health in Johns Hopkins Bloomberg School of Public Health. His
Harvard Catalyst profile is available here
