2.1. Experimental Animals

Breeder pairs (approximately 30 pairs each Levin OR and OS rats were obtained from Taconic (Taconic, Hudson, NY, USA) at 5–7 weeks of age. These outbred strains of Sprague Dawley rats were originally obtained by Taconic from B.E. Levin after 20 generations of selective breeding for rapid weight gain on sucrose and moderate fat (32%) (SUMO32) [8]. These rats were subsequently outbred using a rotational breeding scheme for an additional 30+ generations, and were commercially available from the Taconic repository (strain: TacLevin:CD(SD)DIO, stock #DS; TacLevin:CD(SD)DR, stock #DR). In-house breeding was conducted using the Poiley rotational breeding scheme, in which breeder pairs are systematically rotated in each breeding cycle [9]. Pups were weaned at 3 weeks of age and were immediately switched to SUMO32 diet (Supplementary Table S1). Rats were maintained on a 12 h light/dark cycle at 24 ± 2 °C with 30% relative humidity, and given ad libitum access to SUMO32 diet and distilled water until they were randomized to experimental groups. All animal studies were performed in accordance with the Colorado State University Institutional Animal Care and Use Committee.