Poor lifestyle practices such as smoking and alcohol consumption, unhealthy diet, and physical inactivity are key behavioural risk factors for non-communicable diseases, which get exacerbated due to environmental stressors such as exposure to air pollution and heat. In this work, we assess their relative importance in affecting three non-communicable diseases - heart disease, diabetes, and high blood pressure among the adult Indian population. We also propose a new framework to assess the combined impact across various demographic subgroups. Leveraging data from the National Family Health Survey and satellite and reanalysis products, we identify key risk factors for the urban and rural male populations compared to females, people from the unserved category compared to those from the reserved category, and poor and middle-class families compared to rich families. Our results provide policymakers with pivotal information to focus on the identified critical risk factors for the targeted demographic subgroups, aiming to reduce the non-communicable disease burden and achieve health equity in India. The framework is generalizable and can be applied in other countries for similar purposes.