We propose a new approach to guide health promotion practice. Health promotion should draw on 2 related systems of reasoning: an evidential system and an ethical system. Further, there are concepts, values, and procedures inherent in both health promotion evidence and ethics, and these should be made explicit. We illustrate our approach with the exemplar of intervention in weight, and use a specific mass-media campaign to show the real-world dangers of intervening with insufficient attention to ethics and evidence. Both researchers and health promotion practitioners should work to build the capacities required for evidential and ethical deliberation in the health promotion profession.