Though countless fad diets promise a trimmer physique, the old-fashioned route of portion control and calorie consciousness may be the way to go after all, a new study suggests.

In an experiment with 24 young women, researchers found that the study participants ate far fewer daily calories when their meal portions were trimmed down or when they traded in some calorie-dense dishes for less rich substitutes - all without their feeling deprived.

Both diet tactics - portion control and lower-calorie options - were effective and “additive,” meaning women took in the fewest calories when they practiced both, the study found.

In fact, the two together sliced a whopping 812 calories, on average, from the women’s daily intake, according to findings published in the American Journal of Clinical Nutrition.

What’s exciting about the results, lead study author Dr. Barbara J. Rolls told Reuters Health, is that the calorie plummet came without “huge changes” to the diet, and without leaving the women feeling hungry at the end of the day.

The diners still enjoyed brownies, potato chips and cheese and crackers, albeit lower-fat versions.

It’s thought that life in a land of plenty - especially cheap, super-size portions of calorie-dense foods - is fueling the rise of obesity in the U.S. and other nations. Calorie density refers to a food’s number of calories pound for pound. A pound of broccoli, for instance, has far fewer calories than a pound of chocolate.

Past research has shown that portion size can play a vital role in a person’s calorie intake; if there’s more food on the plate, more food goes into the stomach - even if the diner could feel satisfied with less.

But calorie-density is also key, according to Rolls, a professor of nutritional sciences at Pennsylvania State University in University Park.

And, in fact, cutting calorie density without cutting portions was more effective in this study than simple portion control.

The 24 women, who ranged in age from 19 to 35, followed each of four menu plans for two days apiece. One plan had them eating standard portions of common foods like muffins, pizza, pasta and salad. Another gave them lower-calorie versions of these same meals - reduced-fat snack food, for example, or dinners containing a larger proportion of vegetables.

A third eating plan gave the women full-calorie fare but smaller servings, while the fourth included both portion control and lower-calorie foods.

The researchers found that all three of the diet-conscious tactics cut the number of calories the women ate each day, but the combination of portion control and calorie-watching was most effective, lowering their calorie intake by 812 calories a day.

Controlling calorie density was, however, more effective than eating smaller servings of richer foods. The former cut an average of 575 calories from the women’s daily intake, while portion control trimmed their daily calories by 231.

Rolls said the “message” here for restaurants is that lowering the calorie density of their meals, and less so the size, may be the wiser move. Customers may feel cheated by the sight of skimpier servings, she noted, but may not notice the lower calorie density.

At home, Rolls said, people can trim the calorie density of their meals by adding more vegetables to the plate, or by having a light soup or large salad as a starter.

SOURCE: American Journal of Clinical Nutrition, January 2006.