David Brill
Measuring the distribution of fat in the liver could help identify obese patients who are most in need of treatment, a new study suggests.
The researchers characterized a subset of people with "metabolically benign obesity," who, despite their increased weight, do not seem to be at high risk of diabetes and atherosclerosis.
These patients, comprising around a quarter of the obese subjects in the study, had comparable insulin sensitivity and carotid intima media thickness to normal-weight people.
Ectopic fat in the liver was the strongest predictor of this phenotype and could therefore be used for risk stratification of obese patients, according to lead author Professor Norbert Stefan.
"Clinicians are seeing so many obese people now that they really need to try and focus their resources on those who need treatment earliest. By identifying those who are not in such high need they can put them on more moderate treatment," said Stefan, who heads a research team at the University of Tübingen in Germany.
MRI scans showed that the benign obese group had on average 54 percent less fat accumulation in the liver than insulin-resistant obese subjects (4.3 percent vs. 9.5 percent). The presence of ectopic fat in skeletal muscle was also a determinant of insulin sensitivity.
By measuring visceral adiposity – a known predictor of type 2 diabetes and cardiovascular risk – researchers were able to differentiate between insulin-sensitive and insulin-resistant subjects in the normal-weight and overweight groups. However, visceral adiposity was a weak predictor among the obese.
Doctors should assess patients for all the classical risk factors for cardiovascular disease and diabetes and then consider using MRI to measure liver fat in those deemed to be at high risk, Stefan said. Liver enzymes and ultrasound can also help to provide an assessment, he added.
The study, published in The Archives of Internal Medicine, comprised 314 white subjects with an average age of 45. [2008 Aug 11;168:1609-16]
Stefan stressed the importance of putting out the right public health message regarding the study’s findings.
"This is the start – it identified an important new target but we still need to tell the metabolically healthy obese people that they can’t lean back and say ‘okay that’s it, I’m not at risk.’
"Every obese person needs treatment, even the metabolically benign, because we’re not sure whether the endpoints are that they have a lower risk of dying or developing disease," he said.
A second study, published in the same edition of the journal, looked at the association between cardiometabolic abnormalities and obesity in a cross-sectional sample of 5,440 US adults. The researchers found that 31.7 percent of obese people were metabolically healthy, while 23.5 percent of normal-weight people were in fact metabolically unhealthy. [Arch Intern Med 2008 Aug 11;168(15):1617-24]
Stefan’s research, meanwhile, is now looking at the parameters that regulate the accumulation of liver fat. A larger 2-year study involving 400 people is currently ongoing and is expected to be completed early next year, he said.
Stefan stressed the importance of putting out the right public health message regarding the study’s findings.
"This is the start – it identified an important new target but we still need to tell the metabolically healthy obese people that they can’t lean back and say ‘okay that’s it, I’m not at risk.’
"Every obese person needs treatment, even the metabolically benign, because we’re not sure whether the endpoints are that they have a lower risk of dying or developing disease," he said.
A second study, published in the same edition of the journal, looked at the association between cardiometabolic abnormalities and obesity in a cross-sectional sample of 5,440 US adults. The researchers found that 31.7 percent of obese people were metabolically healthy, while 23.5 percent of normal-weight people were in fact metabolically unhealthy. [Arch Intern Med 2008 Aug 11;168(15):1617-24]
Stefan’s research, meanwhile, is now looking at the parameters that regulate the accumulation of liver fat. A larger 2-year study involving 400 people is currently ongoing and is expected to be completed early next year, he said.
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