Monday, May 27, 2013
A new study finds that compared with Europeans or Americans, Inuit living in Greenland have high mean values of subcutaneous fat, which is thought to represent a more favorable pattern of adiposity
This may help explain why Inuit appear to have better cardiovascular risk profiles than other populations, even when they are obese, researchers say. At the same time, however, the Inuit have levels of visceral fat similar to those in other populations. Visceral fat is known to be linked to adverse metabolic outcomes, and this, together with the high rate of obesity seen among Inuit, might explain why rates of type 2 diabetes are elevated in this population, say the researchers. "Diabetes is a complex disease… The rapid growth in obesity and a possible susceptibility to [developing] diabetes due to a relative insulin deficiency means that diabetes is a major health problem in Greenland, even if the Inuit may be protected [by] a favorable fat distribution," lead author Marit Eika Jørgensen, MD, PhD, from the Steno Diabetes Center, in Gentofte, Denmark, said. The current findings improve knowledge of the mechanisms leading to diabetes in this Arctic population, she said, "and may contribute to our understanding of the north-south gradient in diabetes" in general. For various age groups, the prevalence of diabetes among the Greenland Inuit is approximately 50% higher than in the general Danish population, according to Jørgensen. Among these Inuit, increasing levels of obesity are linked with worse levels of metabolic risk factors (such as cholesterol and blood pressure), but to a lesser extent than is seen among Europeans. These population-level differences might be due to differences in the pattern of fat distribution, the researchers hypothesized. To investigate this, they conducted a cross-sectional analysis among 3108 adult Inuit living in 22 towns and villages in Greenland from 2005 to 2010, who had a mean age of 44 years (range, 18 – 95), of whom 56% were women. The participants received a standard 75-g oral glucose-tolerance test. Visceral and subcutaneous fat were measured by ultrasound. Nine percent had type 2 diabetes, and 79% of these cases were newly diagnosed. Visceral fat was associated with glucose intolerance and insulin resistance, independent of body mass index (BMI) or waist circumference, whereas there was a trend toward no association or an inverse association between subcutaneous fat and these measures of glucose metabolism. The large waist sizes in the Inuit population — a mean waist of 91 cm in men and 90 cm in women — were largely due to subcutaneous fat. "We don’t know the exact mechanism behind this pattern of fat distribution among Inuit, but it is suggested that subcutaneous fat deposition could be a useful adaptation to cold," Jørgensen explained. Ethnic differences in fat distribution may partly explain why the risk of diabetes or cardiovascular disease associated with a certain level of obesity differs in various populations, she added.