Obesity by choice revisited: Effects of food availability, flavor variety and nutrient composition on energy intake

Abstract

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

Body fat distribution and organ weights of 14 common strains and a 22-strain consomic panel of rats

“…In this study, our goal was not to study diet and obesity, even though relative to typical laboratory chows, the diet we chose has a slightly higher energy density (15.9 vs. ~13 kJ/g) and more carbohydrate (68% vs. ~59% of total energy) from sucrose compared with laboratory chow. Based on comparisons made in mice [45], the AIN-76A diet appears to be more “obesigenic” than chow but not nearly as much as the high fat diets typically used to produce obesity. Therefore our study does not specifically model dietary obesity, and the rats maintained a low-to-average proportion of body fat, e.g., less than 20% in most cases.…”

Differential effects of chow and purified diet on the consumption of sucrose solution and lard and the development of obesity

“…The liquid sucrose and chow and the chow, liquid sucrose, and fat groups consumed more energy than the chow and fat and the chow only groups. This coincided with the chow and liquid sucrose group having a similar body weight as the chow, liquid sucrose, and fat group but a higher body weight than the chow and fat and the chow only groups [14]. A similar model of diet induced weight gain has been associated with changes in hypothalamic neuropeptide expression and the development of glucose intolerance and insulin insensitivity [15, 16].…”

“…When combined with chow, the physical form of sucrose and fat affect preference because rats consume more energy from sucrose when consumed in liquid form compared to solid, but consume more energy from fat in solid form compared to oil [11, 12]. Liquid sucrose has previously been shown to promote overeating in chow fed rats by Castonguay et al[13] and Ackroff and Sclafani [14] and lard by Ackroff and Sclafani [14]. The latter study found that a chow, 32% liquid sucrose solution, and fat (vegetable shortening) group did not increase energy intake compared to a chow and liquid sucrose group.…”

Genetic Variation and Effects on Human Eating Behavior

“…However, it has also been postulated that presenting more of the same highly palatable food (such as five bottles of 32% sucrose) results in more overconsumption (139). This is, however, under debate, because others could not reproduce these findings (1).…”