Nearly a third of African-American and Latino children are overweight and most of these have at least one risk factor for type 2 diabetes or heart disease, researchers from the Keck School of Medicine of the University of Southern California will report today.
The statistics come from the preliminary findings of investigations into patterns of metabolic change among Latino children and teens, being presented at the annual meeting of the North American Association for the Study of Obesity (NAASO).
The USC research team are urging the nation to help Latino children who are being hit especially hard by a vicious circle of obesity, insulin resistance, metabolic challenges and heightened disease risk.
"Obesity is now a critical, common nutritional problem in children," said Dr Michael I. Goran, professor of preventive medicine and physiology and biophysics at the Keck School."It disproportionately affects minority groups and is the major contributor to the recent emergence of type 2 diabetes among children. We need to do something now to understand and prevent these chronic diseases."
Latinos are twice as likely as non-Latino whites to develop diabetes and many children are now being diagnosed with type 2 diabetes - once exclusively an adult disease - during puberty.
Funded by the NIH, the Keck School researchers are studying more than 200 healthy Latino children ages 8 to 13 in Los Angeles. They revealed that nine of every 10 overweight Latino children had at least one risk factor for cardiovascular disease and type 2 diabetes, and this appears due to low sensitivity to insulin. Three out of every 10 kids had three or more features of the metabolic syndrome: obesity around the belly, low levels of HDL cholesterol, high triglycerides and high blood pressure.
Higher insulin sensitivity was tied to higher HDL, and lower insulin sensitivity was linked to higher tryglyceride levels and blood pressure. Since these are risk factors for cardiovascular disease and type 2 diabetes, researchers suggest that increasing insulin sensitivity is crucial for preventing chronic disease in childhood.
Overweight Latino children with the metabolic syndrome were also much less physically fit than kids with no metabolic syndrome features-regardless of body composition or sensitivity to insulin. Metabolic syndrome strongly predicts both cardiovascular disease and type 2 diabetes, so researchers believe that improving fitness would be a worthy way of deterring these diseases among such children.
About 28 per cent of heavy Latino children with a family history of type 2 diabetes already have pre-diabetes-elevated blood sugar levels - linked to beta cells (cells in the pancreas that create insulin) that have started failing. Overweight kids who had elevated blood sugar levels, or impaired glucose tolerance, had poor beta-cell function that deteriorated with age. Impaired glucose tolerance was especially common among children whose mothers developed type 2 diabetes during pregnancy, also called gestational diabetes.
"We knew this was a high-risk population, but the extent of these risk factors and the magnitude of the health problems was bigger than we expected," said Goran, associate director of the USC Institute for Prevention Research. "These overweight children are effectively 'walking time-bombs', and the metabolic basis of these risk factors must be targeted in interventions."
The study is not the only one to highlight the severe epidemic facing children in the US. Research presented yesterday from the University of North Carolina at Chapel Hill shows that more than 2 million US adolescents became obese and another 1.5 million remained obese as they grew into adulthood between 1996 and 2001. During the same period, only 271,000 dropped below weight levels considered that excessive as they aged out of their teen years.
"This research highlights the critical nature of the adolescent and young adult period for developing and continuing obesity," said Dr Penny Gordon-Larsen, assistant professor of nutrition at the UNC schools of public health and medicine. "During that transitional period, the proportion of adolescents becoming and remaining obese is particularly high. Preventive and treatment efforts are critically needed."
Gordon-Larsen and colleagues analyzed nationally representative data collected from thousands of US adolescents enrolled in the UNC-based National Longitudinal Study of Adolescent Health study, also known as the Add Health project.
They studied information gathered in 1996 from a sample of 9,561 teens from across the nation during the second data collection wave of the study and then again measured the heights and weights of those same teens five years later when they were aged 18 to 26 during the project's third wave. The team determined obesity among the subjects using age and sex-specific criteria from the 2000 Centers for Disease Control growth charts and International Obesity Task Force reference data.
"Our key findings included the large incidence of obesity, particularly among black and Hispanic females," Gordon-Larsen said. "Over the five-year exam period, 18 per cent and 15 per cent of them respectively, became obese."
"At the beginning, 11 per cent of teens studied were obese, and as they aged and became young adults, 22 per cent were obese," the scientist said.
Older adolescents had a higher rate of obesity and were more likely to remain obese than their younger counterparts, she said. The population shift in body mass was evident in the higher body mass index range.
Changing the US culture and environment to make diets healthier, increase exercise and improve lifestyle choices for Americans of all ages, but particularly those at highest risk - minority populations that are under-served in health care - should become a national priority, Gordon-Larsen said.
The scale of the problem suggests that even with preventative measures being taken now, a large part of the US population will need weight loss treatment and help managing glucose levels in the future.