All patients scheduled to undergo elective, first-time cardiac surgery will be considered for eligibility to participate in the study. As well, a patient whose BMI is less than 18.5 kg/m2 and classified as underweight by the World Health Organization will be excluded. Only those patients who are classified as being normal weight range or overweight and/or obese may be considered for eligibility to participate as defined by the study objectives regarding post-operative cardiac surgery outcomes in obese patients. Patients in the normal weight range classification will be included as a baseline control participant cohort. Finally, patients over the age of 75 will be excluded so as to eliminate the role that advanced age may play in affecting functional capacity.