Indonesia faces a sustainability paradox in its food system, on one side consumer-level food waste is high while many households still struggle to access affordable nutritious diets. As the largest and most digitally immersed cohort, Generation Z of Indonesia is a key leverage point for UN SDG 12 achievement. This dissertation examines sustainable food consumption and food-waste behaviour as interrelated issues using three survey. Study 1 applies Item Response Theory to validate the measures and rank consumption motives and sustainable behaviour indicators from easier to harder to endorse, then uses K-means to derive motive-based segments (n=1,160). Study 2 uses two-stage PLS-SEM to test higher-order sustainability values and influencer review exposure via hedonic and utilitarian attitudes in predicting traditional food consumption intention as an affordable way to achieve sustainable consumption among young Indonesian (n=1,292). Study 3 extended the Theory of Planned Behaviour in food-delivery settings testing how price promotions, food-waste knowledge, and price consciousness relate to sustainable food waste management behaviour (n=561). Results shows: (1) The IRT calibration proved that the consumption motives, sustainable food choice, and food waste management indicators discriminate well and can be ordered by how easy versus hard they are to endorse (Baseline expectations, Emergent engagement, High-barrier signals, and Shared ideals); the clustering yields four motive-based segments (Frugal Indifferent Foodies; Health-focused Independent Locavores; Holistic Demanders and Eco-friendly Enthusiasts; Epicurean Pragmatist Waste-conservers); (2) Traditional food consumption intention shaped by sustainability values as higher order constructs, mostly through utilitarian evaluation; influencer review exposure contributes both directly and through attitudinal pathways; (3) In food delivery context, price promotions do not move waste management on their own; they matter only when filtered through price consciousness and perceived behavioural control. Knowledge works indirectly, while subjective norms show the most consistent indirect link to shape behaviour. Sustainable-related stakeholder's interventions should be segment-specific, value-led and utilitarian in framing with influencer support, and food delivery platform-enabled through perceived behavioural control, subjective norms combined with price promotion offers.