Obesity risks start before birth

Today, one of every three U.S. children is overweight — but it's much easier to prevent obesity than to treat it. That's why pediatric obesity experts now say intervention should begin early — very early. The risk of becoming overweight or obese, it increasingly seems, begins before a child is born, establishes roots in infancy and may be entrenched by the time a tot starts kindergarten.

The notion that a lifelong weight trajectory might be programmed so early is startling, says Dr. Nicolas Stettler, associate professor of pediatrics and epidemiology at the University of Pennsylvania.

Each of the three early-life stages comes with the chance to intervene, breaking a lifetime cycle of obesity and dieting before it starts.

Prenatal

Almost half of U.S. women today begin pregnancy overweight or obese, automatically increasing the likelihood that their babies will be born either too small or too large, both of which increase the risk of obesity for the child later in life. Further, studies show that how much weight a pregnant woman gains and whether she develops gestational diabetes can influence her child's weight in adulthood.

The odds of being overweight at age 7 were 48 percent higher for children of women who gained more weight than recommended during pregnancy compared with women who met weight guidelines, according to a study by Stettler and colleagues published in 2008 in the American Journal of Clinical Nutrition.

Infancy

It may be a baby's weight at age 1 that matters most, experts say. Weight that is too high for the child's height can spell trouble.

A study by Dr. Elsie M. Taveras, an assistant professor of population medicine and pediatrics at Harvard Medical School, published last year in Pediatrics, found that rapid increases in weight-for-length measurements during the first six months of life were associated with a greatly increased risk of obesity at age 3.

No one is sure why rapid weight gain in the first year is important. It could be that when a baby is fed more than it needs, the brain's development is affected so that it signals the need for excessive amounts of food, Stettler says. Likewise, too much food might program an infant's pancreas, and the body's response to insulin, in a manner that leads to obesity.

Whatever the cause, Taveras says, "excessive weight gain in those first six months of life is not baby fat that is going to go away."

Early childhood

In a study published recently in Pediatrics, a team led by Asheley Cockrell Skinner, an assistant professor of pediatrics at the University of North Carolina School of Medicine, found that obese children as young as age 3 had higher levels of C-reactive protein, a marker for inflammation that is linked to heart disease in adults. C-reactive protein levels can rise for a number of reasons, and about 15 percent to 20 percent of children have above-normal levels. But among obese 3-year-olds, 45 percent had elevated levels. It's not clear yet whether this inflammation remains high in obese children or causes any long-lasting harm.