Cognitive decline in older adults is a major public health issue. The cost of caring for older adults with substantial cognitive impairment, like those with Alzheimer's Disease in the US is approximately $200 billion a year, causing major societal, economic, and caregiving burden. Despite great advances towards diagnosing these problems, the discovery of effective treatments has been minimal. Exploring non-pharmacological interventions, such as exercise and healthy living, have gained momentum. These promising, modifiable lifestyle interventions have the potential for delaying disease onset and slowing decline in cognition. However, the therapeutic effect of lifestyle interventions in patients with mild cognitive impairment, a prime intervention period for treatment, is not well understood. Therefore, in this study, the investigators will examine brain, body, and cognitive changes in older adults who engage in moderate-aerobic walking or healthy living education.