This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The main goal of this study is to determine whether the amount of fat loss (achieved through controlled underfeeding) affects the magnitude of improvement in aerobic function (maximal aerobic capacity and endurance) in response to a standardized exercise training stimulus that follows current recommendations for older persons. Secondary goals are to examine whether fat loss is necessary to elicit improvement in specific cardiovascular disease (CVD) risk factors, and to examine whether improvements in functional and CVD risk factor outcomes are related to the degree of total fat loss, as well as to reductions in fat accumulation in skeletal muscle (inter-muscular fat) and surrounding visceral organs (abdominal visceral and pericardial fat). We will accomplish these goals by conducting a 3-arm, 5-month randomized, clinical trial in 180 older (65-79 yrs), obese (BMI=30-34.9 kg/m2), sedentary men and women. Participants will be randomized to an exercise training intervention (moderate-intensity treadmill walking, 4 d/wk) alone (EX Only), exercise with moderate caloric restriction (-250 kcal/d deficit) designed for low weight loss (EX+Low CR;~4.5 kg weight loss), or exercise with intensive caloric restriction (-600 kcal/d deficit) designed for high weight loss (EX+High CR;~10.9 kg weight loss.