Recent work suggested that the energy intake and weight gain of rats maintained on chow and 32% sucrose solution could be increased by simply offering more sources of sucrose (Tordoff, 2002). In Experiment 1 this procedure was replicated but the effect was not: rats given one bottle of sucrose and five bottles of water consumed as much sucrose as those given five bottles of sucrose and one of water. Adding different flavors to the sucrose did not increase intakes further in Experiment 2. The relative potency of sucrose and other optional foods was studied in Experiment 3. Sucrose solution stimulated more overeating and weight gain than fat (vegetable shortening), and offering both sucrose and shortening did not generate further increases in energy intake. Finally, foods commonly used to produce overeating and weight gain were compared. Sucrose was less effective than a high-fat milk diet, and offering cookies in addition to the milk did not increase energy intake further. The nature of optional foods (nutrient composition and physical form) was markedly more important than the number of food sources available to the animals, and is a better contender as the reason for "obesity by choice".
KeywordsFood choice; Variety; Fat; Sugar The widespread availability of tasty, inexpensive, energy dense foods, which are typically rich in sugar and fat, is thought to contribute to the increasing prevalence of human obesity [e.g., 26,32]. A useful animal model for this phenomenon exists: laboratory rats overeat and gain excessive weight when offered a cafeteria of palatable high-fat and high-sugar foods in addition to their nutritionally complete chow diet [e.g., 34,36,37]. Another potentially important variable in diet-induced obesity studies is the availability of food, e.g., the number of sources of food offered [43]. In confirmation of prior studies [e.g, 16,29,40], rats offered a 32% sucrose solution in addition to chow and water consumed more total energy (sucrose + chow) and gained more weight than rats given only chow and water. The surprising finding of Tordoff's study was that rats given access to five bottles of sucrose and one of water consumed significantly more sucrose and total energy than did rats given only one bottle of sucrose and five bottles of water. This is seemingly a situation that mimics the human case of abundant palatable food, with a larger number of sources leading to greater overeating. Tordoff [43] suggested that this was related to the overeating observed in cafeteria studies.Beyond the contributions of sugar and fat per se, variety in the available foods and their flavors has been linked to overeating and obesity in humans and animals [e.g., 27,28,36]. Laboratory
