I am always amazed at my grandmother's instinct to cook exactly the right amount of food for one day. Leftovers are considered unhealthy in her part of India. In such a humid climate, bacteria can bloom on unsuspecting scraps of dal, rice, or sabzis (vegetables). Electricity is unreliable, so refrigerators can unexpectedly turn off for hours (recently, my grandmother contracted a terrible case of pancreatitis, most likely a fluke event from food left a few minutes too long in a broken fridge). So she cooks exactly the right amount in the morning, and the food she makes lasts for both lunch and dinner. The rare bits of excess are given to the downstairs watchman or the maid.
When she teaches me to cook, it seems like more of an art than a science - measurements are imprecise, measured by coin-sizes or "this much of your palm." But she knows exactly how much tamarind is needed for a family of four to eat sambar for two meals. When she peels squash to put in vegetable kootu, she grinds up the peelings with spices and lentils to make a delicious chutney-like condiment (the Tamil spelling of which I cannot possibly transliterate accurately). Food that can be left out overnight is the type that beautifully, healthily ferments (dosa batter, yogurt).
Reducing food waste is not only a matter of economy, it is a matter of health. Cooking every day and building the instinct to cook only the amount we will consume - these are my grandmothers' skills that I hope to learn someday.