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Ethnicity influences body type and disease risk

Obesity and type 2 diabetes are both considered global epidemics. Worldwide, more than one billion adults are overweight (300 million are obese), and more than 285 million people have diabetes. 

Despite their prevalence, however, these conditions do not carry the same risk for all populations. Research suggests that ethnic background may influence an individual’s risk for type 2 diabetes. 

Studies have already demonstrated that certain ethnic backgrounds show significant differences in amounts of body fat and lean mass. In 2007, Dr. Scott Lear, PhD, of Simon Fraser University in Vancouver, BC, reported the results of the Multicultural Community Health Assessment Trial (M-CHAT), a study that investigated the relationship between ethnic background and body composition as it relates to risk for type 2 diabetes and cardiovascular disease. The trial demonstrated that men and women of Chinese and South Asian origin have a higher amount of visceral adipose tissue at a similar body mass index than those of European origin. South Asians also had a greater per cent of body fat. 

At the time, Dr. Lear speculated that these differences might be related to insulin levels, insulin resistance and increased risk for type 2 diabetes. 

In a follow-up study published last fall in the Endocrine Society’s  Journal of Clinical Endocrinology & Metabolism , Dr. Lear’s team measured insulin levels and compared the amount of total body fat-to-lean mass in 828 men and women of Aboriginal, Chinese, European and South Asian origin (ethnicity was based on self-report). The results confirmed that ethnic differences in lean mass do occur, with South Asians having significantly less lean mass than Aboriginal, Chinese, and European adults of the same body size. In addition, the amount of total body fat-to-lean mass was higher in South Asian men than in Chinese and European men, and higher in South Asian women than in Aboriginal, Chinese and European women. Dr. Lear’s research also demonstrated that differences in fat-to-lean mass among the ethnic groups accounted for a substantial variation in insulin levels and insulin resistance. 

“We need to build awareness that this body type — with higher fat mass and lower muscle mass — may put South Asians at an increased risk for insulin resistance and diabetes,” says Dr. Lear. “An individual might appear to be thin and healthy but still be at high risk for diseases we usually associate with obesity.” 

The Canadian Diabetes Association’s 2008 Clinical Practice Guidelines recommend that members of high-risk populations — including people of Asian, South Asian, Aboriginal, Hispanic, and African descent — be screened for type 2 diabetes more frequently and earlier than the general population (i.e., every three years beginning at age 40). 

Dr. Lear’s research suggests that these groups may also require screening in the absence of apparent overweight or abdominal obesity. “If people in these ethnic groups become as overweight as the general Canadian population, their rates of diabetes will be far greater than the general population’s,” he warns. 

“In populations at increased risk for diabetes, interventions that reduce fat mass and increase muscle mass, such as caloric restriction and regular exercise, should be investigated.”