Association Between Childhood Weight Loss and Adult Obesity (Contextual Question 1) (2024)

Concerns about child and adolescent obesity are due in large part to the potential link to adult obesity and associated morbidity. We did not identify any studies that provided direct evidence on the effect of improvements in child weight outcomes on the likelihood of adult obesity. However, an association between childhood weight loss and lower risk of adult obesity is suggested by ten-year outcomes for 176 children with obesity in four randomized family-based obesity treatment studies.267, 314 Study participants were 6 to 12 years of age at baseline (mean, 10.4 years), so the average age at followup was 20 years. At baseline, children were 49.9 (SD 17.2) percent overweight on average, with an average zBMI of 2.8 (SD 1.1). Based on these statistics, we estimate that almost all youth in these studies would have been above the 95th percentile for BMI, with approximately 85 percent meeting obesity criteria as a conservative low-end estimate. At 12 months after baseline, 39.1 percent of children achieved a BMI value below the 95th BMI percentile, and 23.7 percent were below the 85th BMI percentile. At 10-year followup, 47.5 percent and 22.2 percent of children were below the 95th and 85th BMI percentile, respectively. The magnitude of zBMI changes shows similar long-term success of treatment. At 12 months, 73.7 percent and 46.5 percent of children achieved at least a 0.5 and 1.0 zBMI unit reduction, respectively. At 10-year followup, 66.7 percent and 44.4 percent of children achieved at least a 0.5 and 1.0 zBMI unit reduction, respectively.

There is also substantial evidence from cohort studies presented in several systematic reviews that childhood obesity typically persists into adulthood. A 2005 systematic review evaluated 19 longitudinal cohort studies (retrospective or prospective) that reported on weight measurements in childhood and adulthood.19 The review found correlations between child (ages 6 to 11 years) and adult (up to age 37 years) BMI measures ranging from 0.36 to 0.73 in white males and from 0.21 to 0.63 in white females. Correlations between child and adult measures ranged from 0.28 to 0.68 for black males and from 0.28 to 0.65 in black females. Childhood BMI showed stronger tracking into adulthood in children who were older than 8 years, were more overweight, or had one or more parents with obesity. Correlations between adolescent (ages 12 to 18 years) and adult BMI measures were generally higher than for childhood measures, ranging from 0.58 to 0.81 in white males aged 17 to 18 years, from 0.63 to 0.81 in white females aged 17 to 18 years, and from 0.37 to 0.72 in black males and females aged 13 to 17 years. Data on tracking of BMI in children aged 2 to 5 years were limited, but generally showed that tracking into adulthood was minimal. Sex differences in tracking were not consistent across ages. The probability of having obesity as an adult (ages 18 to 37 years) was about 50 percent for children and adolescents (ages 5 to 17 years) between the 85th and 94th BMI percentile, and about 70 percent for those at or above the 95th BMI percentile.

A 2008 systematic review examined the evidence on the persistence of childhood overweight from 18 prospective or retrospective longitudinal studies with anthropometric measurements during childhood or adolescence (ranging from birth to age 19 years) and adulthood (ranging from age 18 to 54 years).315 All the included studies reported that youths who were overweight or had obesity were at increased risk of becoming overweight or having obesity in adulthood. When limited to only high-quality studies, the relative risk of overweight children becoming overweight or having obesity in adulthood ranged from 1.9 to 10.1. For children with obesity, the odds ratio ranged from 1.3 to 22.3. The percentage of overweight adolescents who became overweight or developed obesity in adulthood ranged between 22 percent and 58 percent, and the percentage of adolescents with obesity who became overweight or developed obesity in adulthood ranged between 24 percent and 90 percent.

A 2011 meta-regression analysis on BMI tracking included data on 55,072 individuals from 48 articles with BMI measurements in the same persons at two or more time points.56 Correlations between BMI measured in children under age 10 and BMI measured 10, 20, and 30 years later were 0.67, 0.50, and 0.27, respectively. For BMI measurements in children aged 10 to 14 years, correlations were 0.75, 0.60, and 0.40. Correlations for adolescent (age 14 to 18 years) BMI measurements were 0.73, 0.58, and 0.38.

A 2012 systematic review included 24 studies that investigated the association between early (≤5 years) childhood obesity and adult overweight or obesity.316 Almost all studies reported a significant association between childhood obesity and adult overweight or obesity. The review concluded that early childhood obesity (especially after age two) persists into adulthood, so early childhood obesity is a probable early predictor of adult obesity.

A 2015 systematic review and meta-analysis investigated how accurately simple measures of childhood obesity (e.g., BMI) predict obesity in adolescence and adulthood.20 The review included prospective, longitudinal studies with a sample of at least 1,000 children that measured obesity in childhood and again at least 5 years later. Included studies were limited to those reporting data needed to calculate test accuracy; therefore, studies that provided only correlations between obesity measures at different time points were excluded. Twenty-three studies from 16 cohorts were included in the review, and all used BMI to measure childhood obesity. Followup for the studies ranged from 6 to 42 years, with 11 of the 23 studies having followup of at least 20 years. Meta-analyses of twenty studies showed a strong association between childhood obesity and adult obesity, with children with obesity being about five times more likely to have obesity in adulthood than children without obesity (pooled RR, 5.21 [95% CI, 4.50 to 6.02]). The review presents data on the sensitivity, specificity, and PPV for each study to investigate the diagnostic performance of using obesity in children, according to age of BMI measurement, to predict obesity in adults. The review found that children with obesity, and particularly adolescents with obesity, are likely to still have obesity in adulthood. The PPVs for predicting adult obesity from childhood obesity showed that close to 80 percent of adolescents with obesity go on to have obesity as adults, or approximately 70 percent, when adult BMI was measured at age 30 years or older. Approximately 64 percent of pre-adolescents who had obesity also had obesity in adulthood. However, the review demonstrated that childhood BMI is a poor predictor of adult obesity. Sensitivity was less than 40 percent in all but one study, so most adults with obesity did not have obesity in childhood.

In an effort to explain the childhood determinants of adult obesity, a 2011 systematic review examined the evidence on tracking of physical activity and diet between childhood and adulthood.317 The review included five studies with data on diet tracking and 16 studies with data on physical activity tracking. There was evidence for tracking of both of these behaviors, with similar estimates of strength of tracking, lending support to the need for interventions aimed at modifying diet and physical activity behaviors in overweight children. Based on correlation coefficients, the strength of tracking of physical activity into adulthood was stronger for males (range, −0.1 to 0.47; p<0.001 for frequency of activity over 8 years) than females (range, −0.04 to 0.37; p<0.001 over 6 years), increased with age at which the baseline measurements were made, and declined with duration of followup. Correlation coefficients for tracking of food intake were positive in all cohorts and ranged from 0.009 to 0.66.

Although the data reported in the reviews described above are highly variable due to heterogeneity across studies in sample sizes, study design, cutoffs to define overweight and obesity, and the age at which child and adult weight were measured, the results consistently provide support for the persistence of obesity from childhood into adulthood. The long-term data from four childhood obesity treatment studies suggest that weight loss in children with obesity may reduce the likelihood of adult obesity, reinforcing the importance of effective interventions to manage childhood obesity.

Appendix A Table 1Percentage of Children Who Met Success Criteria at 12 Months and 10 Years in Four Family-Based Obesity Intervention Programs267

Outcome12 months10 years
<95th BMI percentile39.1%47.5%
<85th BMI percentile23.7%22.2%
>0.5 zBMI unit change73.7%66.7%
>1 zBMI unit change46.5%44.4%

Abbreviations: BMI=body mass index; zBMI=body mass index z score.

Association Between Childhood Weight Loss and Adult Obesity (Contextual Question 1) (2024)
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