Preference for High-Fat Food in Animals

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.