Impaired glycogen synthase (GS) activation and muscle glycogen synthesis are correlated with decreased glucose disposal in Type 2 Diabetes. To examine if gys1 deletion in muscle is associated with muscle insulin resistance, we generated a conditional, tamoxifen–inducible, muscle-specific knockout mouse model. Glycogen synthase deletion was successful but the phenotype was complicated by tamoxifen-induced weight loss. The aim of the current study was to optimize the conditional GS deletion without the side effects of weight loss. To determine whether the gene knockout was long lasting, 10 week-old Gyslox+/+/Cre-/- (control) and Gyslox+/+/Cre+/- (knockout) mice were fed a diet containing 1 mg/g tamoxifen for six or eight weeks followed recovery period of 1-2 weeks on a standard chow diet. To assess the degree of deletion, GS protein levels were quantified by western blotting. Preliminary results confirmed an 80-90% deletion of GS protein levels after 6-8 weeks of tamoxifen treatment. Furthermore, the deletion was maintained for an additional one or two weeks following tamoxifen withdrawal, which was associated with weight regain. In conclusion, we optimized the inducible, conditional GS protein deletion in muscle. Further studies are ongoing to determine whether the protein excision is preserved and results in glucose intolerance over a period of weeks to months.