| Summary: | Abstract Background Current recommendations for intensive behavioral interventions for childhood obesity treatment do not account for variable participant attendance, optimal duration of the intervention, mode of delivery (phone vs. face-to-face), or address obesity prevention among young children. A secondary analysis of an active one-year behavioral intervention for childhood obesity prevention was conducted to test how “dose delivered” was associated with body mass index z-score (BMI-Z) across 3 years of follow-up. Methods Parent-child pairs were eligible if they qualified for government assistance and spoke English or Spanish. Children were between three and 5 years old and were at risk for but not yet obese (BMI percentiles ≥50th and < 95th). The intended intervention dose was 18 h over 3-months via 12 face-to-face “intensive sessions” (90 min each) and 6.75 h over the next 9 months via 9 “maintenance phone calls” (45 min each). Ordinary least-squares multivariable regression was utilized to test for associations between dose delivered and child BMI-Z immediately after the 1-year intervention, and at 2-, and 3-year follow-up, including participants who were initially randomized to the control group as having “zero” dose. Results Among 610 parent-child pairs (intervention n = 304, control n = 306), mean child age was 4.3 (SD = 0.9) years and 51.8% were female. Mean dose delivered was 10.9 (SD = 2.5) of 12 intensive sessions and 7.7 (SD = 2.4) of 9 maintenance calls. Multivariable linear regression models indicated statistically significant associations of intensive face-to-face contacts (B = -0.011; 95% CI [− 0.021, − 0.001]; p = 0.029) and maintenance calls (B = -0.015; 95% CI [− 0.026, − 0.004]; p = 0.006) with lower BMI-Z immediately following the 1-year intervention. Their interaction was also significant (p = 0.04), such that parent-child pairs who received higher numbers of both face-to-face intensive sessions (> 6) and maintenance calls (> 8) were predicted to have lower BMI-Z. Sustained impacts were not statistically significant at 2- or 3-year follow-up. Conclusions In a behavioral intervention for childhood obesity prevention, the combination of a modest dose of face-to-face sessions (> 6 h over 3 months) with sustained maintenance calls (> 8 calls over 9 months) was associated with improved BMI-Z at 1-year for underserved preschool aged children, but sustained impacts were not statistically significant at 2 or 3 year follow-up. Clinical trial registration The trial was registered on ClinicalTrials.gov ( NCT01316653 ) on March 16, 2011, which was prior to participant enrollment.
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