Fat baby, fat adult: new links discovered

Rapid rates of weight gain during infancy could be linked to obesity later in childhood, researchers from the Children's Hospital of Philadelphia in the US reveal this week.

Researchers from the Children's Hospital, together with the University of Pennsylvania School of Medicine, found that rapid weight gain during the first four months of life was significantly associated with an increased risk of being overweight at age seven, regardless of birth weight and weight at one year of age.

"Early infancy seems to be a critical period for the establishment of obesity. Babies double their birth weight during the first four to six months, so this may be a period for the establishment of weight regulation. A rapid rate of early weight gain may also be related to cardiovascular disease later in life; both conditions often cluster in individuals,"​ said Nicolas Stettler, a pediatric nutrition specialist at Children's Hospital and leading researcher of the study.

The study looked at data for 19,000 children who were born at term gestation between 1959 and 1965 in 12 U.S. cities. The authors used the presently recommended definition for overweight status - a sex-specific body mass index that is greater than 95 per cent of the U.S. population at any given age.

The study also found that with even a modest increase in weight gain of 100 extra grams per month during infancy, the risk of being overweight at age seven was raised by more than 25 per cent. Starting with a birth weight of 7 pounds (3.2 kg), those 100 extra grams per month would result in a weight at age four months of approximately 14 pounds (6.4 kg), compared to approximately 13 pounds (6.0 kg) under a normal pattern of weight gain.

The greatest proportional weight gain in early infancy occurs in the first four to six months after birth. One hypothesis is that this timeframe corresponds to a critical period for the development of biological mechanisms that regulate obesity. Supporting this theory are other studies and animal models showing permanent changes in brain structure and enzyme function that are associated with adult obesity in animals with a rapid neonatal weight gain.

An alternative explanation might be that early weight gain reflects the beginning influence of a genetic predisposition to be overweight, rather than environmental or feeding patterns.

In the past, infancy has not been targeted for obesity prevention, and at this time there are no effective and safe intervention strategies in infancy for the prevention of later obesity. The researchers make no recommendations for treatment. However, they suggest that a focus on early infancy may lead to new hypotheses regarding the origins of childhood obesity and to new approaches to preventing obesity during infancy.

Recommendations for feeding have changed since the 1960s when children were introduced to solid foods at an earlier age, which could explain some of the weight gain seen in the study.

The researchers also found that first-born children and those whose mothers had a higher body-mass index had a higher probability of being overweight at age seven. Both of these associations had been found in previous studies.

Data were obtained from The National Collaborative Perinatal Project, a multicentre cohort study of risk factors for cerebral palsy that collected maternal and infant data at 12 sites strategically located throughout the U.S. beginning in 1959. Because that project collected information on tens of thousands of children from birth up to age seven, the obesity researchers analysed the data for their current study.

Full findings are published in the February issue of Paediatrics.