MEAL PATTERNS OF MACRONUTRIENT INTAKE IN RATS WITH PARTICULAR DIETARY PREFERENCES

In the present study, we examined, via computer-assisted analyses, the nocturnal meal patterns of male albino Sprague-Dawley rats with clear differences in their individual preferences for the macronutrients, protein, carbohydrate, and fat. Rats exhibiting a strong preference for the carbohydrate diet over the 12-h nocturnal cycle (similar to 50% of the group) consumed fewer total calories and relatively small, more frequent meals, compared with rats that preferred protein or fat. Moreover, the first meal of the feeding cycle was identified as being most distinctive in reflecting the individual dietary preferences of these rats. This contrasts with the subsequent meals, which for all rats showed a general trend of increasing proportions of protein and fat and a decreasing concentration of carbohydrate. Only the high-fat rats (similar to 30% of the group) were further distinguished by a particularly large fat-predominant meal in the middle-dark period, which was then followed by smaller fat-rich meals in the late-dark period. These fat-preferring rats exhibited significantly greater body weight gain compared with rats preferring carbohydrate. Additional patterns exhibited by all rats, regardless of dietary preference, included 1) a significant shift in meal composition from one meal to the next, with a specific meal rich in one macronutrient preceded, as well as followed, by meals with considerably lower amounts of this macronutrient; 2) greater satiating effects (longer postmeal intervals relative to meal size) of meals in the early-dark period compared with the late-dark period, regardless of nutrient composition; and 3) weaker satiety associated with fat-predominant meals compared with carbohydrate- or protein-rich meals, particularly in the late-dark phase. This meal pattern analysis shows that individual meals, and presumably their neural and metabolic substrates, clearly differ among rats with distinct dietary preferences, as well as at different periods of the natural feeding cycle.