A highly saturated fat-rich diet is more obesogenic than diets with lower saturated fat content. 
The present study tested the hypothesis that a saturated fatty acid (SFA)-rich diet is more obesogenic than diets with lower SFA content.  In 8 female Sprague-Dawley rats fed a low-SFA canola or a moderate-SFA lard-rich diets at 67% of energy for 26 days, body weight gain, final body weight, obesity index, and food and energy intake were comparable.  Twenty-nine rats were fed canola or high-SFA butter-rich diets (67% of energy) or chow for 50 days; then high-fat feeding was followed by ad libitum low-fat feeding (27% of energy) for 28 days and by a food-restricted low-fat diet for 32 days.  High-fat feeding resulted in a greater body weight gain (P < .04), final body weight (P < .04), and energy intake (P < .008) in butter-fed rats than in canola- and chow-fed controls, after 26 or 50 days.  Ad libitum canola and butter low-fat diets or chow feeding resulted in similar weight change, whereas food-restricted low-fat diets led to comparable weight loss and final weight.  Canola-fed animals adjusted their intake based on diet energy density, whereas lard and butter-fed animals failed to do so.  Abdominal fat (P = .012) and plasma leptin (P = .005) were higher in chow-fed controls than in canola-fed rats, but comparable with those of butter-fed rats.  Prone and resistant phenotypes were detected with high-fat feeding.  In conclusion, only feeding the high-SFA butter-rich diet led to obesity development and failure to adjust intake based on the energy density and preserving body fat even after weight loss.  The high availability of SFA-rich foods in today's obesogenic environment could contribute to develop and maintain obesity.