NEW YORK (Reuters Health) - The amount of fat a person accumulates in relation to their body size as they grow into adulthood, not their birth size or their growth per se, influences their risk of developing type 2 diabetes, results of a new study suggest.
In a study looking at size at birth, adult body size and sensitivity to the blood sugar regulating hormone insulin in young adults, investigators found that an individual's fat mass in adulthood was the only factor significantly related to insulin sensitivity. Reduced insulin sensitivity is a precursor to diabetes.
"Parents of all children, independent of birth size or growth during childhood, should be aware of the risk of fat accumulation in their children," Dr. R.W.J. Leunissen of Erasmus Medical Centre-Sophia, Children's Hospital, Rotterdam, the Netherlands and colleagues conclude.
Low birth weight has been tied to an increased risk of type 2 diabetes, and some investigators have proposed that the acceleration in growth experienced by people who are born small but reach normal adult size has harmful effects on metabolism. It is still uncertain, note Leunissen and colleagues, whether people who are born small but catch up later or those who remain small throughout their lifetimes are at greater risk of type 2 diabetes.
To investigate, the researchers looked at insulin sensitivity in 136 young men and women, some of whom were born small for gestational age and remained short as adults; some who were born small but reached normal height in adulthood; some who were of normal size at birth but grew up to be short adults; and some who were born at normal size and were normal size as adults.
Fat mass in adulthood was the only measurement that showed a significant association with insulin sensitivity, the researchers found. After they used statistical techniques to control for age, sex and body size in adulthood, the group of men and women who were born small but caught up as adults had significantly lower insulin sensitivity than the control group.
Based on the results, Leunissen and colleagues propose a "fat accumulation hypothesis," which states that "an increased accumulation of fat during childhood, independent of birth size, will result in reduced insulin sensitivity."
"Growth acceleration in height and weight as such is not a problem as long as a normal amount of fat is accumulated," they add.
"Our data imply that all individuals, regardless of their size at birth, should try to achieve or maintain a normal fat mass for their body size," the researchers conclude.
SOURCE: Journal of Clinical Endocrinology and Metabolism, February 2008