In this controlled feeding study, subjects will be randomized to one of two experimental. Group A (N=10): will start with control diet (31 mg/kg/day Met; 31 mg/kg/day Cys) for 4 weeks followed by a washout for 3-4 weeks, then a 70% MR diet (9.3 mg/kg/day Met; 40.3 mg/kg/day SAA) for 4 weeks, followed by 3-4 weeks washout period and then a 90% MR diet (3.1 mg/kg/day Met; 34.1 mg/kg/day SAA) for 4 weeks. Group B (N=10): will start with control diet (31 mg/kg/day Met; 31 mg/kg/day Cys) for 4 weeks followed by a washout for 3-4 weeks then a 50% methionine and cysteine restricted (M/CR) diet (15.5 mg/kg/day Met; 15.5 mg/kg/day Cys; 31 mg/kg/day SAA), followed by 3-4 weeks washout period and then a 65% M/CR diet (10.8 mg/kg/day Met; 10.8 mg/kg/day Cys; 21.6 mg/kg/day SAA) for 4 weeks.