Transcriptional profiling coupled with blood metabolite analyses were used to identify porcine genes and pathways that respond to a fasting treatment or to a D298N missense mutation in the melanocortin-4 receptor (MC4R) gene. Gilts (12 homozygous for D298 and 12 homozygous for N298) were either fed ad libitum or fasted for 3 days. Fasting decreased body weight, backfat, serum urea concentration and increased serum non-esterified fatty acid. In response to fasting, 7,029 genes in fat and 1,831 genes in liver were differentially expressed (DE). MC4R genotype did not significantly affect gene expression, body weight, backfat depth, and any measured serum metabolite concentration. Pathway analyses of fasting-induced DE genes indicated that lipid and steroid synthesis was down-regulated in both liver and fat. Fasting increased expression of genes involved in glucose sparing pathways, such as oxidation of amino acids and fatty acids in liver, and in extracellular matrix pathways, such as cell adhesion and adherens junction in fat. Additionally, DE transcription factors (TF) were identified that regulate many DE genes. This confirms the involvement of TF, such as PPARG, SREBF1 and CEBPA, that are known to regulate the fasting response and implicates additional TF, such as ESR1. Interestingly, ESR1 controls several fasting induced genes in fat that are involved in cell matrix morphogenesis. Our findings indicate a transcriptional response to fasting in two key metabolic tissues of pigs that was corroborated by changes in blood metabolites; and the involvement of novel putative transcriptional regulators in the immediate adaptive response to fasting.