Using dietary information from 7,500 U.S. adults, researchers found that those who reported eating plenty of fruits, vegetables, fiber-rich grains and other lower-calorie foods typically ate a larger amount of food than their peers who favored richer fare.

Yet they ate several hundred fewer calories a day, while consuming more calcium, iron, potassium and vitamins A, C, B6 and folate.

In fact, these diners ate fewer calories without cutting out any major food group, the study authors report in the Journal of the American Dietetic Association. By volume, they ate more from most of the main food groups, compared with study participants who had a taste for sugary, fattier foods.

The difference is that the former group often chose foods with low calorie "density," which refers to the number of calories a food has ounce for ounce. A pound of carrots, for instance, carries far fewer calories than a pound of chocolate.

In general, foods that have a high amount of water and/or fiber, such as fruits and vegetables, also have a low calorie density. Water and fiber add to a food's bulk, but contribute few or no calories.

Sugar, fat and flour, on the other hand, pack on the calories, and calorie-dense foods include chips and other snack foods, nuts, sweets and processed or fatty meats.

So while study participants who filled their diets with low-cal fare ate more food by weight, they ingested fewer calories --an average of 425 fewer among men, and 250 fewer among women.

What's more, they also filled up on nutrients, according to the study authors, led by Dr. Jenny H. Ledikwe of Pennsylvania State University in State College.

"These analyses further demonstrate the beneficial effects of a low-energy-density diet," they write.

People can lessen their diet's calorie density, the researchers note, by slipping more fruits and vegetables into the mix--starting a meal with a large salad, for instance, or filling their dinner plates with a larger portion of vegetables and a little less meat. Or, they can have that large slice of pizza, but go light on the cheese and heavy on the vegetables.

Low-fat dairy foods, fiber-rich whole grains and lean meat or meat substitutes are also good choices, according to Ledikwe and her colleagues.

Some past research has suggested that cutting calorie density is a better diet strategy than portion control, since it allows people to eat the same or a greater amount of food by volume. Experiments have shown that when diners see a full plate, they may not even notice the missing calories.