Through years of laboratory testing, Rolls and her colleagues confirmed that people eat a regular volume of food, not a regular number of calories. If you go out for Chinese food, and you typically eat a cup of stir-fry and a cup of rice, you will still want a cup of stir-fry and a cup of rice whether the chef uses a little oil or a lot. If you are used to eating a salad at the beginning of your meal and you skip it, you will want more meat and potatoes for your main course. Our stomachs are set for a certain volume of food, not a certain number of calories.
This means that you should not try to eat less. If anything, you should try to eat more low-calorie, moist foods that provide fewer grams of fat and sugar. Once Rolls' patients get into the habit of eating salads and soups, they sometimes have to be instructed to eat more of the right food to avoid losing weight too fast.
Volumetrics is not a quick weight-loss diet. It's almost impossible to lose more than about 1-2 pounds (up to a kilo) of weight every week on this plan. But the volumetric diet is a lifestyle that can keep weight off indefinitely, without deprivation, restricted choices, or having to buy expensive or exotic foods.