Critical Window for Obesity Prevention Identified

Troy Brown, RN

October 04, 2018

Most obese adolescents experienced the most pronounced weight gain during early childhood, between 2 and 6 years of age; weight gain slowed after that but continued, leading to a higher degree of obesity during adolescence, a large study found.

"Early childhood is the critical age for the development of sustained obesity. This period encompasses the 'adiposity rebound,' the phase in early childhood during which [body mass index (BMI)] starts to increase again, after having reached a nadir after infancy...the specific dynamics and patterns of BMI in this early childhood period, rather than the absolute BMI, appear to be important factors in identifying children at risk for obesity later in life," the researchers write.

The researchers prospectively and retrospectively analyzed the BMI trajectory over time in a population-based cohort of 51,505 children who had at least one clinical visit with a pediatrician during childhood (0-14.9 years of age) and another visit during adolescence (15.0-18.9 years of age).

Mandy Geserick, MSc, from the Center for Pediatric Research, University Hospital for Children and Adolescents, and Leipzig Research Center for Civilization Diseases (LIFE Child), and colleagues published their findings online October 3 in the New England Journal of Medicine.

They stratified participants by age and weight groups. For weight groups, they converted BMI and height to standard deviation (SD) scores and defined groups as underweight (BMI SD score of −5 to < −1.28), normal weight (BMI SD score of −1.28 to < 1.28), overweight (BMI SD score of 1.28 to < 1.88), and obese (BMI SD score of 1.88 to < 5).

For each weight group in adolescence, the researchers retrospectively determined the percentages of participants in each weight group during childhood.

Most adolescents with normal weight had been of normal weight throughout childhood. Most obese adolescents had been of normal weight during infancy; however, 53% of obese adolescents had been overweight (22%) or obese (31%) from age 5 years onward, with a BMI SD score that continued to increase as they aged.

In the prospective analyses, the investigators flipped the approach and stratified participants by their childhood weight group and then calculated the proportion of each group who became underweight, normal weight, overweight, or obese during adolescence. The vast majority (90%) of those who were obese at age 3 years were overweight or obese as adolescents. Among the adolescents with obesity, the highest acceleration in yearly BMI increments was seen between ages 2 and 6 years, with BMI continuing to rise thereafter.

Compared with children whose BMI was stable during childhood, the risk for overweight or obesity during adolescence was higher (relative risk, 1.43; 95% CI, 1.35 - 1.49) for children with high acceleration in yearly BMI increments during early childhood but not during the school years.

Approximately half of those who were overweight at age 2 years or younger returned to a normal weight during adolescence, but for those who were obese at 3 years of age, 90% were likely to be overweight or obese during adolescence. Only a few young children with obesity went back to normal weight. Those who were lean usually remained lean as adolescents.

"The finding that the risk of adolescent obesity manifests by 3 to 5 years of age suggests that nutritional counseling should be considered when exaggerated weight gain persists or emerges after 2 years of age; it would be of value to test the efficacy of early dietary intervention in an appropriate trial," Michael Freemark, MD, from the Division of Pediatric Endocrinology and Diabetes, Duke University Medical Center, Durham, North Carolina, writes in an accompanying editorial. "Counseling could be applied preemptively for families in which the parents are overweight, particularly if there is a history of maternal diabetes or smoking."

Freemark notes that the researchers found higher rates of obesity among children of overweight or obese mothers, yet they did not examine other factors that contribute to childhood obesity, such as paternal overweight and obesity, intrauterine exposure to maternal diabetes, maternal smoking, and formula feeding compared with breastfeeding.

The rate of overweight or obesity during adolescence was higher among those who had been born large for gestational age (43.7%) than among children who had been born at an appropriate weight for gestational age (28.4%) or small for gestational age (27.2%; P < .001). The risk for adolescent obesity was 1.55 times higher (95% CI, 1.38 - 1.74) among adolescents who had been large for gestational age compared with the other groups.

"We are now witness to an evolving epidemic of childhood obesity in the United States and other westernized countries, along with the emergence in young people of serious complications, including insulin resistance, type 2 diabetes, hyperlipidemia, hypertension, and fatty liver disease," Freemark explains.

He continues, "It is an ominous sign that the number of American children with the most severe and recalcitrant forms of obesity has increased progressively during the past 10 years. One hopes that interventions tailored to high-risk children at an early age can help to prevent or limit excess weight gain before obesity becomes irreversible."

"The current study was not designed to determine whether exaggerated weight gain in early childhood is a cause of subsequent obesity or a marker of previous, inherent, or future risk of obesity. Nevertheless, the identification of a critical window for predicting childhood weight gain provides an opportunity for intervention to prevent obesity in children at risk," Freemark writes.

Geserick has disclosed no relevant financial relationships. Several authors report financial relationships including grants, personal fees, and nonfinancial support from various sources including pharmaceutical companies. A complete list of disclosures can be found on the journal's website. Freemark reports receiving grants from Rhythm Pharmaceuticals, American Heart Association, Humanitarian Innovation Fund, and European Commission, and personal fees from Springer Publishing outside the submitted work.

N Engl J Med. Published online October 3, 2018. Abstract, Editorial

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