Study Offers Insights Into Seasonal Weight Gain in Young Children

UC Riverside study focused on first and second graders of year-round elementary schools with obesity intervention programs

Childhood obesity is a serious problem in the United States.Photo credit: Robert Lawton.

RIVERSIDE, Calif. – Childhood obesity is a serious problem in the United States, with nearly 17 percent of children qualifying as obese. Summer vacation weight gain in overweight and obese children is also fairly common.

A question two researchers in the School of Medicine at the University of California, Riverside recently set out to explore was: How do students gain weight seasonally?  Specifically, they asked: Do overweight or obese children react differently over time and over seasons to ongoing on-campus obesity intervention programs than do normal weight children?

To answer the question, Andrew G. Alexander, MD, and Paul E. Lyons, MD, tabulated the weight gains and height gains of 183 first and second graders of two year-round public K-5 elementary schools (schools without summer vacation) in Palm Springs, Calif., every six months for two years: from April 2011 until April 2013.  Both schools had obesity intervention programs in place.

All participants – approximately 86 percent were of Hispanic descent – had eaten standardized, reduced-fat breakfast and lunch during the 24-month period of the study. For the purpose of the study, the researchers designated April to October as summer, and October to April as winter.  They recorded the body mass index (BMI) and BMI percentiles as well as changes in BMI of each participant for each of the four six-month periods.  They also divided the population of children into subgroups, based on the initial BMIs.  (Off-campus behavior pertaining to caloric intake and physical activities was not measured).

Body mass index chart. Credit: Wikimedia Commons.

Body mass index chart. Credit: Wikimedia Commons.

They found that interventions that aimed at reducing the rate of early childhood BMI gain produced “rebound” BMI gains. Further, this was more pronounced in non-obese children, while hardly affecting obese children.  (A diet-induced weight-gain rebound phenomenon is commonly seen in overweight adults who lose weight, only to regain their initial weight regardless of dietary interventions.)

“We found significant BMI gain with possible wintertime increases in non-obese children,” Alexander said. “Obese children did not show rebound BMI gain, BMI seasonal change, or BMI limitations in response to the obesity interventions.  The initial winter rise in BMI of all but obese subgroups of children exceeded the subsequent winter BMI rise, suggesting a rebound BMI gain was present and further increased by a wintertime seasonal BMI gain.”

The study is unique in that it observed the effects of seasonal BMI gains in a high-risk population who were without prolonged separations from the school environment throughout the calendar year. The researchers deliberately chose the two schools for their study because it allowed them to eliminate as a factor the prolonged withdrawal of school-controlled diets and exercise programs that would otherwise occur during the traditional school summer vacation months.

Alexander and Lyons cautioned that on-campus interventions aimed at reducing the rate of early childhood BMI gain may produce promising results initially, but rebound BMI gains could follow.

“We predict that BMI reductions and rebounds will occur in non-obese children, while hardly affecting obese children,” Lyons said. “To maximize opportunities for success, parents need to be vigilant at home about their children’s physical activities and nutritional intake throughout the childhood years.”

The study appeared in the March 2016 issue of the Journal of School Health, and was funded by the Desert Healthcare District of Palm Springs, Calif.

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Additional Contacts

Andrew Alexander
Tel: (951) 827-2074
E-mail: andrew.alexander@ucr.edu

Paul Lyons
Tel: (951) 827-7675
E-mail: paul.lyons@ucr.edu

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