Babies that are longer and weigh more at birth may have a lower risk of developing type 2 diabetes as adults, researchers report.

The findings suggest that efforts to ensure babies are born at normal weights could also help to cut rates of type 2 diabetes, a disease linked with obesity that has become increasingly common in developed countries.

While it is not clear why small babies may be at risk later in life, inadequate nutrition in the womb may permanently affect the programming of the hormone system, Dr. Bryndis E. Birgisdottir from the University of Iceland in Reykjavik and colleagues explain.

People with type 2 diabetes lose sensitivity to the blood-sugar-regulating hormone insulin, which normally clears the blood of sugar and deposits it into cells for use as fuel. As a result, blood sugar levels remain high, putting patients at risk for heart disease, kidney damage, amputations and blindness over the long term.

Several studies have found an association between reduced birth size and diabetes risk. Iceland has one of the highest average birth weights in the world and low rates of type 2 diabetes, despite a higher prevalence of obesity than neighboring countries.

To investigate, the researchers tracked down information on birth weight and length for more than 4,600 adult men and women living in Iceland, aged 33 to 65. They also evaluated them for glucose intolerance or pre-diabetes, a condition marked by elevated blood sugar levels.

Men born longer and heavier had better glucose tolerance after adjusting for current body mass index (BMI), a measure of weight in relation to height used to gauge obesity. Obese people are known to be at higher risk of developing type 2 diabetes.

Women with higher birth weights were also less likely to develop type 2 diabetes as adults after accounting for BMI. For both sexes, adult obesity added to the effect of low birthweight, the researchers report in the August issue of the American Journal of Clinical Nutrition.

"Measures aimed at decreasing the number of low-birth weight infants might to some extent offset the risk associated with adult obesity and help in the battle against the increasing prevalence of type 2 diabetes worldwide," the study concludes.

Overall, 3.4% of men and 2.2% of women in the study had type 2 diabetes, compared with nearly 6% of adults in the US.

Source: Diabetes News: American Journal of Clinical Nutrition 2002.