Dementia is increasing in Australia in line with population ageing and is expected to peak by mid-century. The development of common forms of dementia, including Alzheimer's disease, is associated with lifestyle-related risk factors that are prevalent among middle-aged Australians, including obesity, hypertension, high cholesterol, diabetes and depression. These risk factors can be significantly ameliorated through regular participation in moderate aerobic physical activity (PA). Current national and international guidelines recommend at least 150 min of aerobic PA per week for achieving health protective effects. Lifestyle intervention is a critical area for action as there are currently no medical or pharmaceutical interventions that can halt the progression of common dementias. Physician-patient discussions concerning risk reduction via habitual aerobic PA offers a complementary intervention as part of broader dementia management. Evidence suggests that to achieve the highest rates of adherence to PA, physician advice in primary care should be supported by wider policies, institutions and community services that offer a meaningful referral pathway and patient follow up after initial assessment. International Green Prescription programs provide examples of physician-led interventions in primary care that could inform further action in Australia.