Energy-dense foods and diets have been associated with higher energy intakes (Andrieu et al., 2006) and with higher prevalence of obesity and the metabolic syndrome (Mendoza et al., 2007). By all reports, the energy density of the Western diet is on the rise, as is the consumption of dietary fats (Drewnowski and Popkin, 1997; Popkin et al., 2001; Drewnowski, 2005). In the United Kingdom, dietary fat accounted for an average of 36% of dietary energy for men and 35% for women (Henderson et al., 2003). In France, dietary fat accounted for 37%–42% of dietary energy, with saturated fat providing 16% (Drewnowski et al., 1996; Perrin et al., 2002; Astorg et al., 2004). In the United States, dietary fat accounted for 33%–36% of dietary energy (Allred, 1995; CDC, 2004). Despite public health efforts to lower fat consumption, global consumption of both animal and vegetable fats continues to rise (CDC, 2004; Amuna and Zotor, 2008). Innate preferences for dietary fats seem to be tempered only by incomes.
As incomes rise, developing nations typically replace plant-based diets with more animal fats, vegetable oils, and caloric sweeteners, a phenomenon known as the “nutrition transition” (Drewnowski and Popkin, 1997). Paradoxically, developed nations recommend replacing fat-rich foods with water-laden grains, vegetables, and fruit in order to increase bulk and so reduce the energy density of the diet. Recommendations to reduce dietary energy density are one way to reduce energy intakes in an effort to address the global obesity epidemic (WHO Report, 2003).
The problem is that the palatability and enjoyment of foods are often tied to their energy density and therefore fat content. Energy-dense foods that are rich in fat are more palatable than are many low-energy-density vegetables and fruit (Drewnowski, 1998). High-fat foods, many containing sugar or salt, have an undeniable sensory appeal and are difficult to resist (Folkenberg and Martens, 2003). Energy-dense high-fat diets are consumed in preference to plant-based diets of grains, pulses, and legumes.
There are many explanations for why humans like fat (Drewnowski, 1997a,b). Several physiological mechanisms have been proposed, many of which are based on the strong links found between fat content, palatability, satiety, and energy density. The orosensory properties of fat or fat “taste” seem to be perceived through a combination of taste, texture, and olfaction (Drewnowski, 1997a; Schiffman et al., 1998). Fat is a concentrated source of energy with rewarding postingestive effects (Drewnowski, 1995). The learning of food preferences may be based on associating sensory attributes with the physiologic consequences of ingestion, such as satiety and well-being (Birch, 1999).
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