Yearly BMI changes of children found to be higher during the COVID-19 pandemic

In a recent study published in the Pediatrics journal, researchers assessed body-mass index (BMI) variations during the coronavirus disease 2019 (COVID-19) pandemic.

Study: Changes in BMI During the COVID-19 Pandemic. Image Credit: Paranyu/Shutterstock

Various studies have reported the increase in body weights of children during the COVID-19 pandemic. This could be possibly due to the closures of recreational facilities and schools which results in a decrease in physical activity as well as dietary changes.

About the study

In the present study, researchers evaluated whether the yearly rate of BMI changes in children was higher during the course of the COVID-19 pandemic as compared to the previous years.

The team drew the study population from the Environmental influences on Child Health Outcomes (ECHO)-wide cohort study which comprised a total of 69 pediatric studies across the US. The activities of the human subjects at each cohort site were monitored by institutional review boards. The heights and weights of the children were collected by each group from measurements taken during each cohort visit or by abstraction of medical records, as well as from measurements reported by the participant or their parents.

The team used the height and weight measurements to estimate the BMI values and percentiles. The BMI values were used as an outcome because it was deemed to be the most appropriate measure for the comparison of BMI variations over time. Centers for Disease Control and Prevention (CDC) cutoffs were employed to estimate implausible measures which were subsequently excluded from the study.

The team defined each BMI category as per CDC guidelines that defined childhood weight status according to BMI percentiles corresponding to gender and age: children with a BMI percentile less than 5% were categorized as underweight, 5% to 85% were of a healthy weight, 85% to 95% were overweight, and 95% and above were obese. The COVID-19 “pandemic period” was taken to be the 15-month period between 1 March 2020 and 31 May 2021 while the pre-pandemic period or the baseline was from 1 October 2017 to 29 February 2020. 

Sociodemographic variables were obtained via either self-reporting or abstraction of medical records. The study employed a binary ‘pandemic period’ indicator to show whether a particular BMI value was measured before or during the pandemic period.


The study results showed that among the 1996 children belonging to the primary study sample, the pre-pandemic age was 5.9 years. Among these, almost 50% were female, and 53% belonged to the non-Hispanic White populations, 16% to the Hispanic populations, and 15% to the non-Hispanic Black community. Notably, 70% of the children had a healthy baseline BMI.

The mean BMI value reported in the baseline period was 17.05 while approximately 2.6 BMI measures were estimated per child during the study period. Study measurements were employed to ascertain 80% of the BMI values in the pre-pandemic and 51% in the COVID-19 pandemic period. The BMI measures reported by self or parent and extracted from medical records were 6.3% and 14% in the pre-pandemic period, and 48% and 1.3% during the pandemic periods, respectively.

The team found no increase in the BMI values before the pandemic after statistically adjusting for gender, age, race, baseline BMI category, and type of BMI measure. On the other hand, during the pandemic period, the yearly change in BMI was almost 0.24 higher as compared to that in the baseline period. Furthermore, higher rates of increase in BMI were noted during the pandemic period among obese children as compared to children of a healthy weight.

In comparison to the pre-pandemic period, the annual BMI variation during the pandemic period among children belonging to the obese category was 1.12 higher than those belonging to the healthy category. Moreover, no increase in the rate of BMI variation was observed during the pandemic period among children belonging to the Black or Hispanic communities, or the overweight category.        


The study findings highlighted an increase in the BMI values of children during the course of the COVID-19 pandemic. The researchers believe that the study calls for targeted interventions to tackle the impacts of the COVID-19 pandemic on the physical as well as mental health of the general population.  

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