Manabe Yasuko, Matsumura Shigenobu, Fushiki Tohru
The phenomenon of animals preferring high-fat foods has been accepted as natural behavior. Animals are equipped with fat not only for energy storage, but also for regulation of body temperature and as a source of many hormones. It is reasonable that animals eat and store fat based on physiological demands. On the other hand, eating an excessive amount of fat causes many metabolic diseases such as type II diabetes, atherosclerosis, and cardiovascular disease. Reflecting the current health situation in industrialized nations, fat studies are focused on why we overeat high-fat foods and how we can cope with accumulating body fat. Ironically, many tasty and palatable foods such as snack foods, ice cream, donuts, and so on, contain large amounts of fat. The high palatability of fatty foods has been reported in many articles. Animals, including humans, show a hedonic preference for fat that increases with fat concentration (Drewnowski and Greenwood, 1983; Imaizumi et al., 2000a). When it comes to dietary fat, we cannot regulate proper calorie intake, and so we consume more calories than we physiologically need. In a long-term drinking test for corn oil in mice, the mice continued to prefer corn oil and ingested excess calories beyond their physiological needs (Takeda et al., 2001a). Why are fatty foods so tasty? Why do we lose our desire to balance calorie intake when ingesting fat? Researchers are increasingly interested in studying the palatable features of fat to address these simple questions. Accumulating data suggest that the high palatability of fat can be attributed to many factors, including its texture (Rolls et al., 2003; De Araujo and Rolls, 2004; Kadohisa et al., 2005), flavor (Ramirez, 1993; Kinney and Antill, 1996), taste (Gilbertson et al., 1997; Gilbertson, 1998; Abumrad, 2005; Laugerette et al., 2005; Matsumura et al., 2007), and postingestive effect (Sclafani and Vigorito, 1987; Suzuki et al., 2003). In this chapter, we discuss a wide range of physiological responses to fat, from fat recognition on the tongue to laboratory animal behavior in response to fat.
动物偏好高脂肪食物的现象已被视为自然行为。动物储存脂肪不仅是为了能量储备，还用于调节体温以及作为多种激素的来源。基于生理需求，动物进食并储存脂肪是合理的。另一方面，摄入过量脂肪会引发许多代谢疾病，如II型糖尿病、动脉粥样硬化和心血管疾病。鉴于工业化国家当前的健康状况，脂肪研究聚焦于我们为何过度食用高脂肪食物以及如何应对体内脂肪堆积。具有讽刺意味的是，许多美味可口的食物，如休闲食品、冰淇淋、甜甜圈等，都含有大量脂肪。许多文章都报道了高脂肪食物具有高度适口性。包括人类在内的动物对脂肪表现出享乐性偏好，且这种偏好会随着脂肪浓度的增加而增强（德雷努斯基和格林伍德，1983年；今泉等人，2000年a）。说到膳食脂肪，我们无法调节适当的卡路里摄入量，因此摄入的卡路里超过了生理需求。在对小鼠进行的玉米油长期饮用测试中，小鼠持续偏好玉米油，并摄入了超出其生理需求的多余卡路里（武田等人，2001年a）。为什么高脂肪食物如此美味？为什么我们在摄入脂肪时会失去平衡卡路里摄入量的欲望？研究人员越来越有兴趣研究脂肪的适口特性，以解答这些简单问题。越来越多的数据表明，脂肪的高度适口性可归因于许多因素，包括其质地（罗尔斯等人，2003年；德阿劳若和罗尔斯，2004年；门久久佐等人，2005年）、风味（拉米雷斯，1993年；金尼和安蒂尔，1996年）、味道（吉尔伯森等人，1997年；吉尔伯森，1998年；阿布姆拉德，2005年；洛热雷等人，2005年；松村等人，2007年）以及摄入后的效应（斯克拉法尼和维戈里托，1987年；铃木等人，2003年）。在本章中，我们将讨论从舌头上对脂肪的识别到实验动物对脂肪的行为等一系列对脂肪的生理反应。
