In the face of growing environmental pressures, understanding how governance can promote more sustainable dietary behaviours is increasingly critical. However, a synthesis of available intervention strategies for behavioural change is currently missing. This umbrella review synthesizes findings from 29 reviews published between 2018–2024, assessing effectiveness of governance interventions aimed at reducing consumer-level food waste and shifting diets toward more environmentally sustainable patterns, particularly reducing meat consumption and increasing the uptake of more sustainably produced foods. Using a dual-method approach, combining narrative synthesis and effect direction analysis, we evaluated interventions through the lens of behavioural change theory. A majority of interventions demonstrated positive effects, especially those targeting food waste, which tend to face fewer cultural and motivational barriers than dietary changes such as meat reduction. Information-based interventions were most commonly studied. While they effectively raise awareness and influence attitudes, there is broad consensus that they are insufficient in isolation to drive substantial behaviour change. Interventions that restructure the decision-making context, such as setting vegetarian meals as default, removing trays in canteens, or reducing portion sizes, consistently showed positive effects. Written and verbal cues were effective in reducing food waste, while results were more mixed for meat reduction. Feedback and goal-setting strategies appear promising, but have been evaluated mostly through stated, rather than observed, behaviours. Fewer studies examined incentivising, coercive, or training-based interventions, though these approaches may offer higher impact if implemented appropriately. Overall, the findings highlight the need to combine intervention types to target the full range of behavioural determinants: capability, opportunity, and motivation. We also highlight the need for more rigorous, long-term, and context-sensitive research. Finally, we offer recommendations for policy makers and researchers, emphasizing that consumer-focused efforts must be integrated into a broader, cross-sectoral policy strategy, spanning health, agriculture, environment, and education, to enable substantial change in food consumption behaviours.