Volumetrics

Volumetrics is a weight-loss diet designed by Dr. Barbara Rolls, who teaches nutrition at Pennsylvania State University. This dietary approach allows patients to eat satisfying amounts of food while controlling calories and meeting nutrition requirements.

The types of food emphasized in this program are high in water content, and fiber, such as fruits and vegetables, which allows patients to eat satisfying volumes of food without eating lots of calories. This follows the principal of energy density. Briefly, the amount of calories per gram of food is the energy density of that food. The higher the energy density of food, the more calories per gram of food. So patients design meals with lower energy density foods; thus, they eat more yet consume fewer calories. Fiber has a very low energy density and can also be added to food to lower the energy density. Fat is the most energy-dense food and increases calories dramatically and should be avoided as much as possible. Several large population-based studies have shown that higher energy dense foods tend to be positively correlated to increases in patients' body weights.

Another principal of volumetrics relies on the fact that most people eat the same amount of food by weight day in day out. Additionally, if you eat less food by weight one day, you tend to make that up the next day by eating more food by weight. Therefore, if you lower the energy density of food and eat the same weight of food, you will lose weight. Amazingly, because people eat according to weight, lower calorie foods can bring patients as much satiety as foods with higher energy density.

To teach these principals to patients, Dr. Rolls breaks down food into four categories: Category 1, [Page 782]very low energy-dense foods—energy density less than 0.6; Category 2, low energy-dense foods—energy density between 0.6–1.5; Category 3, medium energy-dense foods—energy density between 1.5–4.0; Category 4, high energy-dense foods—energy density between 4–9.0. Patients need to consume as much as possible of categories 1 and 2 and limit 3 and 4.

The volumetrics approach to a meal not only works by satisfying the patient's need to have a certain weight of food, but it also satisfies the mind by thinking you are eating a normal-sized meal. The bigger the meal, the longer it lasts, thus sending more sensory signals to your brain. Additionally, the larger volume activates more stretch receptors in the stomach, thus increasing satiety.

The principals of volumetrics are classically shown in the casserole experiment. Patients were invited to eat one of three choices: the first was a vegetable-and-rice casserole alone, the second was the same casserole served alongside a 10-ounce glass of water, and the third was a soup made by cooking the water and casserole together. Then researchers measured the quantity of lunch eaten a few minutes later. Compared with intake of the casserole alone, water consumed as a beverage with the casserole provided no additional reduction in lunch intake, whereas incorporating water into the casserole (to make soup) resulted in a 100-calorie reduction in later intake.

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