I am not asking for specific diets or reducing plastic waste. Many people may not want to change their diets.
How do people buy food so that they throw away as little food as possible? There must be people out there with systems or calendars that facilitate as little going bad in the fridge as possible. In America we throw away 40% of our food or something. This is not sustainable as food production and transportation accounts for 10% of energy use, and 25% of methane emitted from landfills. Many people don’t have coops nearby, can't afford them, or can only go to the grocery store once a month due to lack of transportation or distance. It gets more complicated with buying organic and local food because it typically doesn't last as long.
Any system or cultural practice (non-dietary) that might reduce this food waste could be helpful.