According to the June 2007 issue of Consumer Reports, in a study rating the diets, Volumetrics is the best carefully researched diet plan. Volumetrics is based on eating foods with low "energy density"--that is, foods with relatively few calories per portion and high water content (fruits, salads, soups).

Her best-selling book is titled:  The  Volumetrics  Eating Plan. Part weight-control program, part cookbook, it's an effort to put into practical form a lifetime of study on why people eat what they do and how to satisfy the human biological drive for abundant food while achieving a healthy weight.

Pennsylvania State University's Laboratory for the Study of Human Ingestive Behavior is one of the world's most sophisticated centers for the study of what and how humans eat. The queen of this empire is Barbara Rolls, professor and Guthrie chair in nutrition at the university. For nearly three decades, Rolls, 60, has researched food choices, portion sizes, the caloric or energy density of foods, and myriad other factors that influence the human appetite and what satisfies it.

Most recently, the lab has been studying the impact of energy or calorie density--that is, the number of calories in a given weight of food--on satiety and weight control. Rolls calls this research "Volumetrics."

The Volumetrics diet program is based on eating foods with low "energy density"--that is, foods with relatively few calories per portion and a high water content. No foods are "forbidden".

It was Rolls who realized that satiety, or the sensation of fullness, is "food specific." That is, when people are full of one food, they can still eat another--an explanation, says Rolls, "for why you always have room for dessert." She was among the first to notice that humans eat about the same weight or volume of food every day but not the same calories, a notion now accepted by nutrition scientists.

Yet she also discovered an apparent contradiction: When food portions are "supersized," people eat more. Adults offered four different portions of macaroni and cheese at her lab ate 30% more calories when given the largest portion, compared with the smallest. Fewer than half noticed any difference in the serving sizes. Likewise, in Rolls's sandwich experiments, men and women were served 6-, 8-, 10-, and 12-inch submarine sandwiches. When given the 12-inch sub, women ate 31% more calories and men 56% more--compared with those given the 6-inch sub.

Asked to rate their fullness after lunch, diners reported little difference whether they had eaten the larger or smaller sub. In a 2-day study, portion sizes were increased for some dishes by as much as 100%, and people continued to eat more over both days. "As to why people respond this way, I don't know, but that is part of what we're working on," Rolls says. "Clearly, visual and cognitive cues are important."

What has become clear from her Volumetrics studies is that the key to weight management lies in "food choices that help you feel full with fewer calories." The absence of satiety is one reason most "diets" don't work very well or for very long. "Satiety is the missing ingredient in weight management," Rolls writes, and she's impatient with those who say the nation's obesity epidemic can be reversed by "telling people to eat less. People need to eat more low-energy-density food, such as fruits and vegetables, so they get a satisfying amount of food and enough calories."

This view is echoed in the 2005 Dietary Guidelines for Americans. And studies show that encouraging overweight families, for example, to eat more fruits and vegetables results in greater weight loss than telling them not to eat foods high in fat and sugar. "Emphasizing what people can eat rather than what they should not eat seems more sustainable," says Rolls.

Note: Eating lots of fruits and vegetables might fill you up, but water empties out of your stomach quickly, leaving you hungry a few hours later.

In BestDietForMe.com’s opinion, following the principles and suggestions of this diet plan will undoubtedly improve one's general health, as it promotes choosing and eating healthy foods, and eating a well-balanced diet.  The book also encourages incorporating exercise into one's daily routine -- another component of living a healthy lifestyle.  We encourage dieters to consult their physician before beginning any diet plan for guidance on whether it is suitable for you, given your medical history, physical condition, and and medications you may be taking.