South Timothy, Holmes Nathan M, Martire Sarah I, Westbrook R Frederick, Morris Margaret J
Department of Pharmacology, School of Medical Sciences, University of New South Wales, Sydney, Australia.
Department of Psychology, University of New South Wales, Sydney, Australia.
PLoS One. 2014 Apr 21;9(4):e93506. doi: 10.1371/journal.pone.0093506. eCollection 2014.
Obesity is associated with excessive consumption of palatable, energy dense foods. The present study used an animal model to examine feeding patterns during exposure to and withdrawal from these foods.
Male Sprague Dawley rats were exposed to standard lab chow only (Chow rats) or a range of cafeteria-style foods eaten by people (Caf rats). After 1, 4, 7 and 10 weeks of diet in their home cage, rats were subjected to 24-hour test sessions in a Comprehensive Lab Animal Monitoring System (CLAMS). In the first two test sessions, Chow rats were exposed to standard lab chow only while Caf rats were exposed to a biscuit and high-fat chow diet. In the final two test sessions, half the rats in each group were switched to the opposing diet. In each session we recorded numbers of bouts, energy consumed per bout, and intervals between bouts across the entire 24 hours.
Relative to Chow rats, Caf rats initiated fewer bouts but consumed more energy per bout; however, their motivation to feed in the CLAMS declined over time, which was attributed to reduced variety of foods relative to their home cage diet. This decline in motivation was especially pronounced among Caf rats switched from the palatable CLAMS diet to standard lab chow only: the reduced energy intake in this group was due to a modest decline in bout frequency and a dramatic decline in bout size.
Exposure to a cafeteria-diet, rich in variety, altered feeding patterns, reduced rats' motivation to consume palatable foods in the absence of variety, and further diminished motivation to feed when palatable foods were withdrawn and replaced with chow. Hence, variety is a key factor in driving excessive consumption of energy dense foods, and therefore, excessive weight gain.
肥胖与美味且能量密集型食物的过度摄入有关。本研究使用动物模型来研究在接触这些食物以及停止接触后的进食模式。
将雄性斯普拉格-道利大鼠分为两组，一组只喂食标准实验室饲料（饲料组大鼠），另一组喂食一系列人类食用的自助餐厅式食物（自助餐厅组大鼠）。在其笼舍中进食1、4、7和10周后，将大鼠置于综合实验动物监测系统（CLAMS）中进行24小时测试。在前两个测试阶段，饲料组大鼠只接触标准实验室饲料，而自助餐厅组大鼠接触饼干和高脂饲料。在最后两个测试阶段，每组一半的大鼠改为喂食相反的饲料。在每个阶段，我们记录了整个24小时内的进食次数、每次进食消耗的能量以及进食间隔时间。
与饲料组大鼠相比，自助餐厅组大鼠的进食次数较少，但每次进食消耗的能量更多；然而，它们在CLAMS中的进食动机随时间下降，这归因于与笼舍饮食相比食物种类减少。这种动机下降在从美味的CLAMS饮食改为只喂食标准实验室饲料的自助餐厅组大鼠中尤为明显：该组能量摄入减少是由于进食频率略有下降和每次进食量大幅下降。
接触丰富多样的自助餐厅式饮食会改变进食模式，降低大鼠在缺乏多样性时食用美味食物的动机，并且当美味食物被撤下并替换为饲料时，进一步降低进食动机。因此，食物种类是导致能量密集型食物过度消费进而导致体重过度增加的关键因素。
