An online risk reduction intervention to reduce risk of cognitive decline will be compared with a lifestyle modification in obese middle-aged adults in primary care The CRE will fund the evaluation and translation of BBL to the primary care setting (BBL-GP). Primary Care is an ideal setting for the implementation of this program because it is where adults with high risk are identified and is an existing and well trusted context, and fits in with the CREs socio-ecological approach for risk reduction. Within primary care, a key population group for targeting with multi-domain risk reduction interventions are obese, middle-aged adults. Obesity in mid-life increases the risk of cognitive decline and doubles the risk of late-life dementia. BBL-GP engages participants in goal setting and behaviour change processes with the aim of reducing their overall risk profile for and was developed with input from the Consumer Dementia Research Committee and other stakeholders. It will be offered to obese patients at the National Health Co-operative, in a randomised controlled trial (RCT; n =240). The National Health Co-operative is the largest bulk-billing practice in the ACT. Participants will be randomised to: 1) BBL-GP Online + Usual care (BBL-GP), 2) a Usual care control group (Control). Primary outcome is the dementia risk score; Secondary outcomes include dementia literacy, physical activity, cognitive engagement, and cognitive function. Cost effectiveness will be evaluated.