Ultra-processed food consumption and BMI-Z among children at risk for obesity from low-income households

Abstract

Objective: To evaluate the association between baseline ultra-processed food consumption in early childhood and child BMI Z-score over 36 months.

Methods: We conducted a prospective cohort analysis as a secondary data analysis of the Growing Right Onto Wellness randomised trial. Dietary intake was measured via 24-h diet recalls. The primary outcome was child BMI-Z, measured at baseline and at 3-, 9-, 12-, 24- and 36-month timepoints. Child BMI-Z was modelled using a longitudinal mixed-effects model, adjusting for covariates and stratifying by age.

Results: Among 595 children, median (Q1-Q3) baseline age was 4.3 (3.6-5.0) years, 52.3% of the children were female, 65.4% had normal weight, 33.8% were overweight, 0.8% were obese and 91.3% of parents identified as Hispanic. Model-based estimates suggest that, compared with low ultra-processed consumption (300 kcals/day), high ultra-processed intake (1300 kcals/day) was associated with a 1.2 higher BMI-Z at 36 months for 3-year-olds (95% CI = 0.5, 1.9; p < 0.001) and a 0.6 higher BMI-Z for 4-year-olds (95% CI = 0.2, 1.0; p = 0.007). The difference was not statistically significant for 5-year-olds or overall.

Conclusions: In 3- and 4-year-old children, but not in 5-year-old children, high ultra-processed food intake at baseline was significantly associated with higher BMI-Z at 36-month follow-up, adjusting for total daily kcals. This suggests that it might not be only the total number of calories in a child's daily intake that influences child weight status, but also the number of calories from ultra-processed foods.

Keywords: childhood obesity; cohort study; nutrition; racial and ethnic minority groups; ultra-processed foods.

Figure 1:. Kernel density estimates of baseline mean daily percent of calories from ultra-processed foods, stratified by baseline age (≥3 years & <4 years; ≥4 years & <5years; ≥5 years).

The kernel density was estimated using the Epanechnikov kernel with a bandwidth of 4.04. Child age has been categorized into groups for plotting in this figure but was analyzed as a continuous variable.

Figure 2:. Model-based estimates of BMI-Z for low and high ultra-processed intakes, overall and stratified by child age.

Plot represents model-based estimates of child BMI-Z for selected representative low and high values of baseline mean child kcals from ultra-processed foods (300 and 1300 kcals, respectively) and for selected child ages. Estimates are from a longitudinal mixed-effects linear regression model, adjusting for baseline child mean daily kcals from ultra-processed foods, mean daily total kcals, age, sex, and mean daily percent of time spent in moderate-vigorous physical activity; parent ethnicity, household food security, WIC/SNAP participation, and random assignment in the original RCT, and with additional interactions involving timepoint and child age. Estimates for selected child ages have been plotted in this figure, but age was analyzed as a continuous variable.