Why are Diabetes Type 2 rates higher in the USA than the UK? Apparently, it is not mainly due to commonly listed risk factors, such as obesity, BMI levels, differences in physical activity, or other lifestyle characteristics, but rather waist size. Visceral fat, the fat people build up around the mid-section (their tummies) is much more closely linked to diabetes Type 2 risk than other factors, according to a report carried out by researchers from University College London, The Institute For Fiscal Studies (London), and the RAND Corporation, a not-for-profit organization headquartered in Santa Monica, California. The report has been published in the latest issue of Journal of Epidemiology and Community Health.
Studies into diabetes type 2 risk should include waist size, or fat accumulation in the mid-section of the body, as well as other commonly used risk factors, the authors write.
Co-author, James P. Smith, corporate chair of economics at RAND, said:
Americans carry more fat around their middle sections than the English, and that was the single factor that explained most of the higher rate of diabetes seen in the United States, especially among American women. Waist size is the missing new risk factor we should be studying.
Although middle-aged Americans have a similar standard of living to their English peers, only 11% of English males report having diabetes compared to 16% of American males. 7% of English women have diabetes versus 14% in the USA.
A previous study by the same authors had shown that despite spending over twice as much on health care as the British, American middle-aged people are less healthy.
The investigators in this latest study examined lifestyle characteristics of British and American people and found no significant differences that could explain this variation in diabetes risk. They looked at such factors as BMI (body mass index), smoking prevalence and socio-economic status. All conventional diabetes type 2 risk factors were fairly similar in both countries.
What they did find was that US males have waists 3 centimeters larger than their English peers, on average. The waists of American women are 5 centimeters bigger than their English counterparts.
The authors report that the waist-size difference, across most BMI categories appeared to be more closely linked to diabetes risk than anything else. Even among women of normal weight, 41% of American females had a high waist size category compared to only 9% of their English peers.
Higher waist circumference explains a large part of the greater prevalence of diabetes among American males, and in the case of females the waist-size link explains virtually the whole difference in diabetes risk, the authors concluded.
Why do Americans have larger waists than their English peers? The authors believe the following may explain some of the reasons:
- Americans are less physically active
- The American diet is more likely to give you a bigger tummy than the British diet
- Some environmental factors, such as levels of stress may be different in the USA compared to the UK
Further research is required to find out why this link between waist size and diabetes risk occurs, and why this risk factor is stronger than the more conventionally listed ones. Some studies have shown, for example, that mid-section fat (visceral fat) has a different metabolism from fat elsewhere in the body.
Visceral fat, also known as abdominal fat, organ fat or intra-abdominal fat exists inside the abdominal cavity, in between such organs as the stomach, liver, intestines and kidneys.
Visceral fat is different from subcutaneous fat which exists under the skin, or intramuscular fat with is interspersed in the skeletal muscles. The fat people have on their thighs and buttocks (lower body) is subcutaneous. Fat in the mid-section (abdomen) is visceral.
Central obesity refers to an excess of visceral fat – the individual’s abdomen protrudes excessively – his/her tummy sticks out. Several studies have identified a link between excess visceral fat and a higher risk of developing cardiovascular disease, inflammatory disease, insulin resistance and diabetes.
Before the menopause, a female’s sex hormones encourage the storage of excess fat in the hips, thighs and buttocks. After the menopause, due to hormonal changes, fat migrates to their waists. Because males have a different hormonal make up, they are more likely to store excess fat in the belly, even when they are relatively young.
Sources: Rand Corp., Journal of Epidemiology and Community Health.
“What explains the American disadvantage in health compared with the English? the case of diabetes”
James Banks, Meena Kumari, James P Smith, Paola Zaninotto
J Epidemiol Community Health doi:10.1136/jech.2010.108415
Written by Christian Nordqvist