What’s less likely to derail your diet: a big bowl of frozen yogurt or a small chocolate chip cookie? If you guessed the cookie, you’re right—and you’re in the minority. In one recent survey, 62% of people said that the kind of food you eat matters more than how much you eat when you’re trying to lose weight. But new research on portion control says that’s wrong. A study in the American Journal of Clinical Nutrition found that women who shrank their portions by 25% slashed 250 calories a day—enough to help them lose a half-pound a week—and still felt full. Ready to downsize? Here are five easy ways to get started.

Trim your trigger foods
Most people typically overeat two or three favorite foods—usually pastas, breads, meats, snacks, or sweets, says Stacey Nelson, MS, RD, LDN, senior clinical nutritionist at Massachusetts General Hospital in Boston. It may be that we love the taste, nosh mindlessly in front of the TV, or just hang on to a childhood habit. Nelson’s tip: Get to know recommended serving sizes for your favorites, and stick to them as closely as you can. Butter your bread, for instance, with a pat no bigger than a large postage stamp, says Lisa R. Young, PhD, RD, professor of nutrition at New York University and author of The Portion Teller. A serving of fish (3 ounces) should be the size of a checkbook, a serving of steak should look like a deck of cards, and a potato serving should be no bigger than a computer mouse. (For more comparisons, visit EatRight.org and search for “portion sizes.”)

If those portions sound frustratingly small, start slowly. Eat a few spoonfuls less of rice and pasta, or go with half a sandwich instead of a whole. Cutting portions of foods with hefty calories helps you cut calories, period, says Barbara J. Rolls, PhD, professor of nutritional sciences at Pennsylvania State University. And fewer calories equal fewer pounds. Bonus: As long as you don’t go overboard, this simple lifestyle change lets you eat almost anything (we didn’t mention that cookie for nothing).

See less, eat less
“We eat whatever portion is placed before us,” says David Levitsky, PhD, an obesity researcher at Cornell University in Ithaca, N.Y. So the trick is to avoid seeing more food than you want to eat. This strategy worked for Susan Pedersen, 40, of Wichita, Kan. By immediately putting away food after serving herself the right-size portions, she skipped second helpings and lost 35 pounds. “I’d cook only one portion of meat or serve about a cup of spaghetti and then refrigerate the leftovers,” she says. “The rest of the meal would be salad with a low-fat dressing and some fruit.”

Tweak this approach for snacks. Place a small amount of pretzels in a bowl instead of grazing from bags or boxes. And freeze tempting treats like brownies. They won’t call out from the cupboard.

Shrink your plates
Try eating dinner on smaller side plates; you’ll have less to eat. “When I eat off of a salad plate, I still feel full. It definitely works,” says Suzanne Rapp, 33, an equity trader in Boston who shed 10 pounds in less than three months.

Don’t like salad plates? Try dishware designed to keep your portions in check. Mesü ($50; 973-582-4208 ) offers a stylish six-piece porcelain set that features pastel graphics on the bottom to indicate portion sizes from ½ to 2 cups and pastel lines inside to tell you when to stop piling on the pasta (or whatever).

Create your own after-meal ritual
Brush your teeth. Chew a piece of sugarless gum. Or sip a hot drink like tea or sugar-free cocoa. These rituals can be cues to stop eating and should help curb the impulse to indulge in seconds or dessert, Nelson says.

Try practicing mind over munching
Overeating is often a psychological problem. These mind games may help.

• Think of meat and pasta as side dishes. For instance, fill half your plate with broccoli and cauliflower, a quarter with chicken, and a quarter with linguine.
• Imagine you’re treating your body like a trash can when you polish off morsels you don’t really want. Yuck.
• Many of us are programmed to eat in “units” (one sandwich, one yogurt, etc.), notes a new study in Psychological Science. If that sounds like you, stick to small units. Chances are, you won’t go back for another—or back to your old dress size.