Severe Obesity in Toddlers: A Canary in the Coal Mine for the Health of Future Generations Free

In this issue of Pediatrics, Zhao et al¹  report a small but significant increase in the prevalence of severe obesity among the 16.6 million children aged 2 to 4 years participating in the Women, Infants, and Children (WIC) program between 2016 and 2020. This represents a reversal of previous decreases in severe obesity among this same group from 2010 to 2016. Severe obesity in childhood is defined as having a BMI ≥120% of the 95th percentile, which approximates 2 SDs above the mean. It is critical to note that the development of severe obesity this early in life is nearly irreversible.

Gesserick et al modeled accelerated BMI increase in early childhood and risk of sustained obesity, finding that 90% of children who develop obesity by age 3 will still have obesity by adolescence.²  Severe early-onset obesity is correlated with earlier and more severe risk for chronic disease; Lycett et al demonstrated that high BMI at age 2 is associated with increased metabolic syndrome risk score at age 11.³ 

Severe obesity is different than milder forms of overweight and obesity; reliable and representative national data show that severe obesity in childhood is strongly associated with high blood pressure, dyslipidemia, prediabetes, and early mortality.⁴  Thus, these new data from Zhao et al showing reversal of previous progress, with an increase in severe obesity in children aged 2 to 4 years, is a cause for great concern for policymakers, clinicians, and public health professionals.

Currently, there is little understanding about what effectively treats obesity before age 6 years. The 2023 American Academy of Pediatrics Clinical Practice Guidelines (CPG) for the Evaluation and Treatment of Children and Adolescents with Obesity is based on graded evidence review of >16 000 studies evaluating treatment of children with obesity.⁵  Of these, only 40 studies included any children aged <5 years (and only 13 included 2-year-olds), all involved behavioral counseling, and few demonstrated effective BMI reduction.⁶  In the final recommendations, treatment options for children under aged <6 years include motivational interviewing (strong evidence) and intensive health behavior and lifestyle treatment (moderate evidence). None of the pharmacotherapy or surgical trials included in the CPG involved children <5 years; it is unclear whether these options will, or should, ever be used among preschoolers.

Prevention of early life obesity involves addressing multiple interrelated factors with different drivers. Malihi et al measured various social and behavioral factors among infants at age 9 months to determine which factors influenced excess weight gain by age 4.5 years.⁷  Of multiple factors considered, food insecurity (FI) (relative risk [RR] 1.32) was most strongly associated with obesity, followed by sleep duration of <11 hours a day (RR 1.3), daily consumption of fast food or soft drink (RR 1.25), and screen time >1 hour a day (RR 1.22). All combined, these 4 factors accounted for 43% of obesity risk in this population by age 4.5 years. Thus, effective prevention of early life obesity will need to target multiple behavioral and social drivers to be successful.

FI and obesity have a complex relationship; although it seems paradoxical that decreased access to food would lead to increased adiposity, multiple studies have confirmed a positive relationship between FI and obesity in adults, particularly among women.^8,9  A proposed explanation is that FI leads to financial trade-offs, with basic needs (eg, housing) forcing the purchase of cheaper foods that tend to be energy-dense but with low nutritional value.¹⁰  Indeed, adults¹¹  and teens¹²  with FI have poorer dietary quality as compared with food-secure peers. A 2022 systematic review of FI and obesity among infants and young children found an association for those experiencing multiple episodes of FI, younger age at the time of FI, and among girls.¹³  Females at all ages are at higher risk for developing obesity in the setting of FI; the reasons for this are unclear; suggested hypotheses involve biologic and metabolic responses, or social factors including stress and anxiety, in response to hunger and food scarcity.¹⁴  Poverty plays an important role in the association between obesity and FI. Data from the Early Childhood Longitudinal Study show a mixed association between FI and obesity in younger children; however, this cohort had a low overall prevalence of FI (1.2% between kindergarten and middle school).¹⁵  By comparison, a study including a low-income sample of nearly 30 000 infants (59% racial or ethnic minority group) with a baseline FI prevalence of 24% found that FI was associated with a 22% greater odds of child obesity as compared with matched infants living in food-secure households.¹⁶  FI is also associated with less successful obesity treatment of children, challenging even our limited options for treatment in this age group.^17,18 

It will be important to continue the surveillance initiated by Zhao and colleagues in this early childhood and low-income group. However, these data are likely to underestimate the current prevalence of severe obesity in toddlers. The time period evaluated in this study does not capture pandemic-related changes. During the coronavirus disease 2019 (COVID-19) pandemic, BMI increased at double the previous rate, particularly for children who had obesity before the pandemic.¹⁹  In addition, these data do not include children who qualify for WIC but are not enrolled, a group that is at greater risk of FI than the rest of the population. Over 50% percent of US children qualify for WIC, and although 82% of those who qualify are enrolled in infancy, this drops to only 57% at 1 year and only 24% by age 4.²⁰ 

These findings suggest strategies that may be explored in future research. First, the most evidence-based nutrition program aimed at preventing FI in young children is the WIC program.²⁰  Although WIC participation is associated with improved child diet quality and may improve household food security, WIC has not yet demonstrated effectiveness in preventing or reversing early life obesity.²¹  One explanation is that the benefits are simply not enough. Future data from the COVID-19 pandemic years may provide some insights. In the year after the onset of the COVID-19 pandemic (February 2020 and February 2021), waivers permitted the use of remote enrollment and benefit issuance, as well as certain flexibility in products. Over this period, WIC participation increased by 9.7% for children.²²  In March 2021, the American Rescue Plan included a provision that increased the WIC package from $9 per month for children to $35 per month, specifically focused on fruits and vegetables. Although this increase was temporary, the multiple extensions may allow adequate time for future data to examine differences in BMI and FI with these increased benefits.

Next, given the strong association between FI and future obesity at this early age, future obesity prevention and treatment research may include policies or interventions to treat FI in novel ways. Questions remain as to how and in what way food and nutrition can be most effectively delivered. For example, how much additional food assistance is needed to overcome FI? Should that assistance be provided with restrictions (eg, limited food choice) or no restrictions (eg, child tax credit)?

Although many questions remain, the urgency to act quickly and with a focus on social drivers of health is clear. Interventions, whether aimed at preventing or treating early life obesity, will be most effective if they follow the general principles of the 2023 American Academy of Pediatrics CPG, including whole-child care, addressing social and structural drivers of health, and providing nonstigmatizing options for families.

COVID-19

coronavirus disease 2019

CPG

Clinical Practice Guidelines

FI

food insecurity

RR

relative risk

WIC

Women, Infants, and Children