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Hypothesis Beta t-statistics p-value f² Effect Size Result
H8: PSE→INT 0.127 1.975 0.048 0.013 Small Supported
H9: PB→INT 0.270 4.481 < 0.001 0.055 Small Supported
H10: PR→INT -0.108 2.363 0.018 0.016 Small Supported
H11: SE→INT 0.285 5.029 < 0.001 0.097 Small Supported
Not
H12: CTA→INT 0.084 1.258 0.208 0.007 Small
supported
H13:
FM→PSU→INT 0.102 3.328 0.001 - Supported
H14: Not
FM→PSE→INT 0.035 1.813 0.070 - supported
H15: FM→PB→INT 0.092 3.850 < 0.001 - Supported
H16: FM→PR→INT -0.041 2.192 0.028 - Supported
H17: FM→SE→INT 0.101 3.965 < 0.001 - Supported
H18: Not
FM→CTA→INT 0.015 1.037 0.300 - supported
Source: Analysis results from SmartPLS 4.1

Table 4. Predictive Relevance
Construct PSU PSE PB PR SE CTA INT

Q²predict 0.260 0.067 0.110 0.136 0.121 0.025 0.139
Source: Analysis results from SmartPLS 4.1

4.4. Discussion
The findings indicate that FOMO acts as an important psychological driver that
reshapes several components of the extended Health Belief Model (eHBM) in the context
of online dietary supplement consumption among Vietnamese Gen Z. Specifically, FOMO
positively influences perceived susceptibility, perceived severity, perceived benefits, self-
efficacy, and cues to action. These results are consistent with the argument of Przybylski
et al. (2013), suggesting that the fear of missing out on rewarding experiences enjoyed by
others can increase individuals’ sensitivity to social information and intensify the urgency
to engage in health-protective behaviors (Zhao et al., 2024; Tang et al., 2024).
This influence may be further amplified in digital environments where social
commerce platforms continuously distribute personalized content. As users are
frequently exposed to health-related information and dietary supplement promotions,
perceived health risks may become more salient, while the perceived benefits of such
products are reinforced through social proof from the user community.
However, a notable finding of this study is that although FOMO significantly
influences cues to action, this factor does not directly affect purchase intention. This
suggests that Vietnamese Gen Z, despite being responsive to digital stimuli such as
livestream promotions or short-term discounts, still tend to base their purchasing
decisions on internal cognitive evaluations. Purchasing decisions are therefore shaped
not only by external stimuli but also by considerations such as financial constraints,
product safety concerns, and individuals’ confidence in searching for and evaluating
information (self-efficacy).
Furthermore, the mediating role of eHBM components indicates that FOMO

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