Your book says the United States wastes 50 percent more food now than it did in the 1970s. Why is that?
Portion sizes have grown tremendously since then. Plus, it’s become normal for restaurants and caterers to produce excessive menus and buffets and for consumers to buy more than they need.

We’ve come to expect large amounts of food.
Yes. Research NRDC has done found that people are not comfortable with empty white space on plates or in fridges or grocery carts. There’s an urge to fill those spaces with food. And in our culture, throwing food out is acceptable. In fact, leaving something on your plate is considered posh.

What else contributes to food waste?
A lot of produce won’t get picked for market because it’s not pretty enough to be sold. It gets tossed or turned into the soil.

What’s the environmental impact?
About 70 percent of our water and 50 percent of our land is devoted to agriculture. So when we’re not eating that food, it’s a huge unnecessary use of resources. About 33 million cars’ worth of greenhouse gases are produced to grow food that never gets eaten.

What types of food get wasted most?
Fruits and vegetables. Tied for second are dairy products and bread. Meat is third, but it has the biggest impact. If you throw out a hamburger, that’s the equivalent of taking a 90-minute shower, in terms of the water it took to produce it.

How can we waste less produce?
If you need small amounts of specific fruits or veggies for a recipe, buy them from the salad bar so the excess won’t rot in your fridge. Or buy frozen versions, which have almost the same nutritional value with none of the pressure.

What else can we do?
Be realistic. What tends to happen is you buy all these groceries on the weekend because you’re feeling aspirational about how much you’re going to cook. But by Wednesday, life has happened and you’re ordering takeout. And then the broccoli goes bad. Instead, plan for that. If you can, shop often and buy less.

How else can we be conscientious shoppers?
Use a shopping list or an app. And take a last look in your cart before checking out. Think about when in the near future you’re going to eat each item. If you don’t have a clear answer, don’t buy it.

You also talk about conducting a “waste audit.”
For two weeks, jot down what you throw out to pinpoint what you are wasting and why. Did dinner plans change? Did you get wooed by a sale and buy too much? Write down the cost so you feel the financial pain.

How closely should we follow expiration dates?
Take them with a grain of salt, as they’re not federally regulated. A “use by” or “best by” date typically says when the product will be at its best quality. There may be a change in taste, color, or texture.

So we may be throwing out food that’s still OK?
Yes. A big misunderstanding is that when food is old, it will make you sick. The main reason for illness is pathogens like salmonella and E. coli that contaminate food at the farm or processing plants.

What do we need to be careful of?
Mold, green potatoes, and rancid meat, oil, or nuts.

What are some ideas to use up food?
Toss a mishmash of items into a tortilla or in fried rice or pasta salad. You can also sauté wilted lettuce with butter and garlic. Even if you waste a little bit less, it’s still an accomplishment.