Diet and Nutrition Claims

Vegetables are high in water, and the idea is to increase people's intake of watery foods so that they fill up without consuming excess calories--essentially eating more to weigh less. As farfetched as it sounds, this diet--which has been promoted through the media and popular books--may very well be effective.

At the core of the Volumetrics Diet, as it's called, is the notion of energy density, which refers to the number of calories per gram of food. Watery and high-fiber foods such as vegetables, fruits, soups, beans, and nonfat yogurt are low in energy density, while things like cheese, meat, and cookies have a high density.

Human studies in lab settings show that people typically consume about the same volume of food every day. If calories are cut by lowering energy density but the amount of food remains the same, subjects don't feel deprived. For example, in that research where scientists sneaked pureed veggies into entrees to decrease energy density, people reported feeling just as full from these dishes as they did from versions with higher energy densities.

So how does this affect our weight? A cohort study of 50,000 women found that those whose diets increased the most in energy density over the course of eight years gained the most weight. And several randomized studies show that decreasing energy density leads to weight loss. In one of them, which involved 97 obese women, subjects assigned to eat less fat and more water-rich foods shed more pounds after one year than those who just reduced their fat intake. The watery-food group ate more and felt less hungry, which likely made it easier for them to stick to their diets.

Studies show that soup in particular can be effective at filling you up and promoting weight loss. But not just any soup. Broth-based soups such as vegetarian vegetable typically have a much lower energy density than creamy ones like broccoli and cheese, which at some restaurants can tip the scales at more than 500 calories per bowl.

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