Project 3 ?Nutritional strategies for metabolic health in aging The health status of the aging population is negatively affected by sarcopenic obesity as described by the progressive loss of lean tissue and an increase in adipose tissue. This condition presents a clinical conundrum as it predisposes older obese individuals to a high risk for disability, morbidity and mortality. Insulin resistance, chronic inflammation, elevations in intrahepatic lipid and detrimental alterations in the gut microbiome are also evident. The application of caloric restriction-induced weight loss (CRWL) used to address these health risks in younger individuals may exacerbate muscle wasting and increase morbidity in older adults. Unfortunately, low fitness levels and poor compliance limit the mitigating influence of weight loss through exercise training on sarcopenic obesity. In order to address anabolic resistance or the decreased ability to maintain protein synthesis that contributes to sarcopenic obesity, we have developed a complete meal replacement that contains a mechanism-targeted profile of essential amino acids (17 grams). This profile is designed to overcome anabolic resistance and maintain net protein balance even in the hypocaloric state. It is our overarching hypothesis that EMR will promote the retention of lean tissue mass, and improve metabolic and functional outcomes following 12 weeks of CRWL, and that those endpoints will be sustained over a 12 week maintenance period with the once per day (q.d.) consumption of EMR. We will randomly assign older obese individuals to either EMR or an isocaloric serving of Bariatrics Advantage (meal replacement that contains 27 grams of intact protein) during these interventions. We will execute these specific aims to test our hypotheses: SA1. Establish the importance of EMR in the preservation of lean tissue mass during CRWL. Lean tissue mass and adipose tissue mass will be determined by dual energy x-ray absorptiometry (DXA) and magnetic resonance imaging/spectroscopy (MRI/MRS) scans. MRI/MRS will be used to measure intrahepatic lipid, and we will evaluate alterations in insulin sensitivity using the HOMA score. We will measure potential changes in gut microbiota in collaboration with Dr. Duddleston at the University of Alaska Anchorage. SA2. Determine the influence of EMR on physical function and increased daily activity during CRWL. Slow walking speed is a strong predictor of morbidity and mortality. We chose the 6-minute walk test to represent the primary endpoint for this aim. We will also determine alterations in gait speed, skeletal muscle power and strength and stair climbing ability, and changes in physical activity using Actigraph GT3X+ devices. SA3. Identify whether EMR q.d. will sustain improvements in body composition, physical function and metabolic parameters over a 12 week, maintenance period following CRWL. Since the preservation of lean tissue mass is directly linked to optimal function and metabolic health, we will measure the influence of EMR q.d. on the indices of metabolic health (ie., intrahepatic lipid, insulin sensitivity) and physical function.