We investigated the importance of early weight change in a pediatric weight control trial. Children's percentage weight change at FBT session 8 was associated with weight outcomes after FBT and at 2-year follow-up, although effects were attenuated over time. Specifically, a loss of ~4% to 8% of initial body weight by session 8 was necessary to achieve successful short-term and long-term treatment response (ie, 5% or 10% BMI z
-score reduction). This rate of weight loss is in accordance with expert recommendations25
and, thus, allays potential safety concerns regarding rapid weight loss. Overall, results support the existing literature, which indicates the importance of early weight change in predicting treatment response over time, at least while children are still in treatment and up to 2 years after treatment.
Although children's percentage weight change at FBT session 8 was associated with greater changes in BMI z
score in both the short-term and long-term, early percentage weight change was a more potent predictor of short-term than long-term weight outcome. This result is not surprising, because different skills are required for early weight loss compared with sustained weight maintenance.6,26
That said, successful weight maintenance likely involves building on behavioral skills acquired early in treatment, which may explain why early weight change was significantly related to long-term outcome.
Children's early treatment response was associated with early FBT attendance. This may be because better attendance early in treatment contributed to mastery of weight loss skills, which in turn promoted early weight change. Future studies should investigate whether children who fail to achieve significant early reductions in body weight would benefit from an alternative treatment approach. For example, more individualized attention to factors that inhibit initial progress may be necessary.
It remains unclear why early treatment response is such a potent predictor of overall treatment outcome, although many hypotheses exist. In this study, neither parent nor child psychosocial functioning predicted weight change by session 8. However, parent weight change at session 8 predicted child weight change at session 8, which suggests that similar constructs may promote early weight change in both parents and children (eg, changes to the home environment27
); alternatively, parents' success with their own weight-control behaviors may have provided better modeling for their children. A logical next step is to examine a wider range of psychosocial characteristics in relation to early response. For example, motivation and readiness for change may be important in the initial stages of treatment12
as families prepare to undertake dramatic changes in weight-related behaviors. It will also be important to identify factors (and obtain early and frequent assessment of them) that mediate the relation between early weight change and overall treatment response.
The current study has several limitations. Measures of adherence to targeted weight-related behaviors were not available during FBT, which precluded examination of the behavioral mechanisms by which early change mediated overall treatment response. All psychological measures were administered at baseline, thus reports on 1 measure could have influenced reports on related measures completed in a similar time frame. Finally, although our sample was more racially/ethnically diverse than many previous studies, the largely female and non-Hispanic white sample may limit generalizability of our findings. Nevertheless, the study had several strengths, including a large sample, and the availability of long-term follow-up data. Moreover, this is the first study to report on early weight change in preadolescent children and to examine predictors of early treatment response.
Overall, our findings warrant replication but have several important clinical implications. Because early weight change seems to be a marker for children's long-term treatment response (and one that is both reliable and easily obtained), providers are advised to assist their patients in achieving early weight loss to maximize overall treatment outcome. Children who are unable to achieve early weight loss may require additional encouragement from parents and/or treatment providers to attend treatment regularly and persist with behavioral changes. Future research should identify factors responsible for early weight change and further explore the relation between early response and overall treatment outcome. In summary, early treatment response seems to be an important factor in the ultimate outcome of pediatric weight loss treatment, and warrants further investigation as a means to maximize the long-term effectiveness of existing weight control interventions.