An Experimental Examination of the Role of the Theory of Planned Behavior Constructs in Decreasing Sugar-Sweetened Beverage Consumption

There is an increasing awareness of the public health dangers posed by the consumption of beverages with added sugar. The present experiment was the first to examine the efficacy of manipulating the three primary constructs of the Theory of Planned Behavior (TPB) to motivate reductions in sugar sweetened beverage consumption. More specifically, this experiment examined the effects of combining an intervention designed to increase awareness of the risks of sugar sweetened beverage (SSB) consumption, an intervention designed to establish low SSB consumption social norms, and an intervention designed to increase perceived behavioral control over reducing SSB consumption on college students’ intentions to reduce their SSB consumption, preparations to reduce consumption, and actual changes in SSB consumption. A total of 430 college students were randomly assigned to one of eight conditions in a 2 (risks information: control vs SSB risks) x 2 (social norms information: none vs SSB norms) x 2 (implementation intentions task: control vs planning how to reduce SSB consumption) between subjects design. Intentions to alter SSB consumption, a behavioral measure, and measures of attitudes, subjective norms, and perceived behavioral control were assessed immediately following the interventions. At 2-weeks post-intervention, future SSB consumption intentions, behaviors indicative of preparations to reduce SSB consumption, and actual SSB consumption were assessed via a surprise follow-up phone call. As had been expected, each of the interventions resulted in greater intentions to reduce SSB consumption in the future, and there was evidence that the effects of the interventions on SSB reduction intentions were mediated by the TPB constructs. In addition, the results demonstrated that participants in the condition that received all three interventions expressed the greatest SSB reduction intentions, were significantly less likely to take an SSB drink when offered a free beverage and reported engaging in more behaviors indicative of preparations to alter their SSB consumption (e.g., reading drink labels checking for sugar content) compared to those in the other seven conditions combined. Furthermore, the planning intervention produced changes in actual SSB consumption. That is, those who engaged in the SSB planning task during the initial experimental session in the lab reported significantly lower SSB consumption 2-weeks later than did those who completed the control planning task. The three interventions utilized in this experiment showed promise for altering SSB consumption intentions and behavior and, given their brevity and low cost, have potential to be developed into large scale community-based interventions that may lead to meaningful public health benefits.