Helsinki, Finland - Data from child-welfare clinics in Helsinki during the 1930s and 1940s is providing a welcome piece of the puzzle as to how weight and growth in infancy and childhood affects risk of coronary heart disease in adults [1]. A new study indicates that while low birth weight appears to increase the risk of later heart disease—as other studies have suggested—weight gain during the first two years of life may reduce this risk, and later accelerated weight gain can increase it.

"Growth between birth and two years is associated with a reduction in risk of later disease: the more growth, the less heart disease," lead author on the study, Dr David Barker (Oregon Health & Science University, Portland), told heartwire. "But once you get beyond two, the rules change. Then rapid weight gain is associated with increased risk of later disease. So all growth up to two is good, but after two is negative and associated with increased risk."

Barker et al's study focused on 8760 men and women who had been born at Helsinki University Central Hospital between 1934 and 1944 and then attended child-welfare clinics, where their weight and height were measured roughly 12 times between birth and age two, then yearly between the ages of two and 11. The investigators then used hospital records to track coronary heart disease admissions and deaths between 1971 and 1998.

They found that the 357 men and 87 women who died or had cardiovascular events in later life were more likely to have been small at birth and still thin at two years, but then rapidly put on weight as compared with other children their age. Increase in BMI after age two was a better predictor of later coronary events than BMI at any particular age, they found. Of note, however, the authors saw nothing to corroborate the theory that rapid weight gain during the first few months after birth adversely affected coronary risk. As well, specific markers of coronary disease risk—namely insulin, proinsulin concentrations, and serum triglyceride concentrations—were increased in individuals with low birth weight and low BMI at two years but with higher-than-normal BMI increases over the next nine years.

The findings have important implications for identifying children at risk, Barker says. "The practical point of interest is that the children in school who are going to get heart disease are not the fat children; they are thin at two and are putting on weight rapidly but haven't got to the average until around 10. So these children are invisible. We're all concerned about having lots of fat children on the streets of Portland, OR, and that is an issue, but it may not be an issue in terms of heart disease. It's an associated issue, but it's a journey that starts with being thin at age two."

Indeed, Barker hypothesizes that birth weight and timing of weight gain may help explain why some obese adults seem more at risk of coronary heart disease than others. "We're all conscious that some people seem to handle obesity in adulthood and live to a ripe old age, and some people die prematurely. So it would seem from our findings that children who are fat at two, three, four, and five will probably stay fat, but they won't end up in intensive care, whereas the children who were thin but gained weight rapidly will."

Barker says he and his colleagues think the age of two is a turning point of sorts, since it is at around two years of age that muscle development is completed. If babies are born thin or become thin in the first few months of life, what they lack is muscle. "If, thereafter, you put on weight rapidly, you're putting on fat and you end up with a body that may look pretty average, but it's a body that's high in fat and low in muscle and more prone to insulin resistance," Barker posited to heartwire.

Commenting on the study, Dr Matthew Gillman (Harvard University, Boston, MA), who also wrote an editorial accompanying Barker et al's paper, emphasized to heartwire that the findings corroborate earlier work by the same group as well as studies from India showing that accelerated weight gain during childhood increases the risk of coronary heart disease in adulthood [2]. What's new to this research are the observations about birth weight and growth during the first two years.

"The little twist on it is that that accelerated growth during childhood is more harmful if you're born small," Gillman said. "If you are born at a relatively low birth weight, then gaining weight more rapidly during childhood seems to be more harmful."

Still unknown, Gillman says, is what's really happening during those first two years. "That's an important question because pediatricians always want to know, and mothers and fathers always want to know, how big should my baby be? How fat should my baby grow? What should I feed my child for optimal growth, etc?"

Those questions, he says, cannot be answered by this paper, particularly since other studies have suggested that weight gain during the first weeks and months of life, for both premature babies and full-term babies, can lead to being overweight or having hypertension, insulin resistance, and high leptin levels in later life.

For these reasons, Gillman says he does not necessarily accept the hypothesis that two years may represent an important cutoff point.

"I'm not sure I would go that far with these data," Gillman told heartwire. "First of all, they don't have information on fat or muscle or body composition. Second, that cohort was born during the 1930s and 1940s. So we don't know if what's observed in cohorts born back then has any relevance to cohorts born today. There was very little obesity back then, whereas we're facing an obesity epidemic at this point. I think what we can say is that during those first two years of life, there is some controversy, and we need to know more, because that's really important for parents and healthcare professionals."

In his editorial, Gillman emphasizes that the scenario at the center of Barker et al's study—low-birth-weight children who rapidly gain weight in childhood—represents one of the fastest-growing groups in the world.

"This is a phenotype that's becoming more common in the developing world, where the epidemiologic transition consists of kids who were born at relatively lower birth weights who then, in the setting of urbanized, sedentary lifestyles, gain weight faster in childhood," Gillman elaborated to heartwire. As such, he writes in his editorial, the "ominous pattern" that the authors identified "is both common and liable to persist for the foreseeable future."