Liver fat possible metabolic risk factor in obese
MedWire News: Research suggests that at higher levels of obesity, the liver may be a more important pathogenic fat depot, and have a greater impact on the metabolic syndrome, than visceral fat.
Lauren Kim, from the National Institute on Aging in Maryland, USA, and colleagues found that in older adults, visceral adipose tissue (VAT) and liver fat (LF) were both independently associated with the metabolic syndrome, but that VAT was the most important depot at lower levels of overweight, while LF was more important at higher levels.
"This may have important clinical implications, as the better target for monitoring metabolic risk may be waist circumference (a surrogate measure of VAT) in normal weight and overweight adults, and signs of fatty liver in overweight and obese individuals," say the researchers.
The team evaluated associations between the metabolic syndrome and VAT and LF (assessed by computed tomography [CT] imaging) in 1616 women and 879 men (average age 76 years) from the Age, Gene/Environment Susceptibility (AGES)-Reykjavik study.
Writing in the journal Obesity, the researchers report that among women, 37% were normal weight (body mass index [BMI] <25 kg/m2), 41% overweight (BMI 25-29.9 kg/m2), and 22% obese (BMI ≥30 kg/m2), and among men the distribution was 40%, 45%, and 15% across these three BMI groups, respectively.
Normal weight, overweight, and obese women were 2.78-, 1.63-, and 1.43-times more likely to develop the metabolic syndrome, respectively, with every 1-standard deviation (1-SD) increase in VAT.
In men, VAT was only associated with the metabolic syndrome in those who were overweight. But in this group, each 1-SD increase in VAT increased the likelihood for developing the metabolic syndrome by 69%.
In both genders, LF was associated with significantly increased odds of developing the syndrome in the overweight and obese groups. Women were 38% and 45% more likely, and men were 38% and 27% more likely to develop the syndrome, respectively, for every 1-SD increase in LF. However, there were no associations in either gender for the normal weight groups.
When the researchers compared the standardized β coefficients for VAT and LF within and across BMI categories they found that for VAT, values generally decreased across the normal weight, overweight, and obese groups, while estimates for LF increased.
Kim's team say that this indicates that, regardless of gender, the most important fat depot with respect to the metabolic syndrome is visceral fat in the lower BMI range, and LF at higher levels of obesity.
They say: "Fatty liver is a novel metabolic risk factor in overweight and obesity that may be useful for distinguishing individuals who are likely to develop the metabolic syndrome from those who are not."
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By Nikki Withers