Q&A Nibbler Nation

The average American makes more than 200 decisions about food every day, according to Brian Wansink, director of the Cornell Food and Brand Lab. Most of the time we don't even know we're making them--until we discover that our clothes no longer fit. Wansink wants to alert the public to this dietary sleepwalking. His new book, Mindless Eating: Why We Eat More Than We Think (Bantam), is a fascinating look at the hidden psychology of eating, with tips to help people sidestep the fattening ploys of food manufacturers and restaurateurs. TIME's ANDREA SACHS spoke with Wansink.

What do you mean when you write about the influence of the "tablescape"?

The tablescape is everything that is on the table: how the food is arranged, how close it is to us, what the plate looks like. It can also be whether the table is lit by candlelight, spotlight or fluorescent light. The tablescape not only influences how much we enjoy food; it has tremendous impact on how much we eat. We find that people who serve themselves from slightly smaller serving bowls serve themselves a smaller amount. With snacks, they end up taking 50% more if they were served in a large bowl rather than a small bowl. The same thing happens with your plate: 6 oz. of pasta on an 8-in. plate looks like a pretty nice size portion, but the same 6 oz. on a 12-in. plate doesn't even look like an appetizer.

How does offering a wide variety of foods affect our behavior?

If there is more variety, you eat more. At a holiday buffet, you're way more likely to overload your plate. What people should do at buffets is never have more than two items on their plate at any one time. They can go back as many times as they want. This really limits people's tendency to overeat.

Does it help or hurt to eat with other people?

Well, it makes life enjoyable. The danger is that you're going to eat 40% more food if you eat with one other person than if you eat by yourself. You enjoy the food more, and you sit longer. The good news is that you don't have to eat like a monk not to gain weight. If you're at a dinner party, don't start your meal until the last person at the table starts. This delays things a little bit. Or you can use the Rule of Two. There are four things that you can eat at many meals besides the main course: an appetizer, bread, a drink and dessert. The Rule of Two is that you can have any two things you want out of those four. But you can't have three.

A lot of people these days shop in large quantities at Costco or Sam's Club. What effect does that have?

We find that in almost every case, 50% of the food or beverages you buy from one of these clubs is gone within the first seven days. So if you buy a 36-pack of Fritos or a 5-lb. barrel of pretzels, half will be gone in the first week. You can get around this by taking that 5-lb. barrel of pretzels and putting it in smaller ziplock bags or containers.

What do you mean by "the mindless margin"?