High Water Content In Food Decreases Energy Intake In Lean Women

Nutrition Research Newsletter, Nov, 1999

Consuming foods with a high water content more effectively reduces subsequent energy intake than drinking water with food. Water adds weight to food without adding energy, therefore reducing the energy density of the food. The first study to examine the effects on satiety of water served as a beverage and water incorporated into a food was recently completed at Pennsylvania State University.

Twenty-four lean women aged 20-45 years participated in the study. They consumed breakfast, lunch, and dinner in the laboratory one day per week for four weeks. All meals were ad libitum, lunch and dinner were individual, buffet-style, self-selected meals. During all meals subjects were instructed to eat as much or as little as they wished. All foods were weighed before and after consumption to determine the amount consumed by each participant and the macronutrient content. On three of the four days the subjects received a preload before lunch. There were three different isoenergetic preloads: chicken rice casserole, chicken rice casserole served with a glass of water and chicken rice soup. Subjects consumed the preload over a 12-minute period and were served lunch five minutes after completion of the preload, or 17 minutes after they arrived at the laboratory during the no-preload control condition. Subjects rated their hunger, thirst, nausea, and fullness before and after each meal and before and after the preload.

Breakfast and dinner intakes were similar across conditions. The subjects in the control condition consumed more at lunch than in the three preload conditions. Subjects consumed significantly less at lunch when they consumed the soup as the preload than when they consumed the casserole with water or the casserole. Incorporating water into the casserole reduced energy intake, but drinking the equivalent amount of water along with the casserole did not reduce energy intake. There was no difference in energy intake during the two casserole conditions. When lunch and dinner intakes were combined, the total amount of food consumed was significantly less after the soup preload than after the casserole. Subjects consumed on average 33% fat, 49% carbohydrate, and 18% protein. After consumption of the soup the fullness ratings were higher and consumption was lower compared with the other two conditions. There was no relation between thirst ratings and intake.

Increasing the water content of a food can enhance the effect of the food on satiety, therefore reducing energy intake. Energy intake five minutes after a preload of chicken rice soup was 26% lower than after the chicken and rice served in a casserole form, without the water. Intake at dinner did not increase to adjust for the difference in the lunch intake. Researchers speculate that the soup, served in a large cup, appeared to be a larger portion than the casserole, which was served in a small bowl. Visual cues may have led subjects to associate the soup with a high degree of satiety.

Barbara J. Rolls, Elizabeth A. Bell, Michelle Thorwart, Water Incorporated into a Food but Not Served with a Food Decreases Energy Intake in Lean Women, Am J Clin Nutr 70:448-455 (October 1999) [Correspondence: B. J. Rolls, Nutrition Dept., 226 Henderson Building, Pennsylvania State University, University Park, PA. 16802-6501. E-mail: bjr4@psu.edu.]