Programs and devices addressing energy balance (EB) available to consumers typically monitor only selected elements of the EB equation such as diet or physical activity (PA). This project will develop a prototype - MyBalance- of an integrated cell phone and web-based system for near real-time assessment and intervention on EB. The MyBalance website will suppport initial customization through user entry of height, weight, and sex (to estimate user's resting metabolic rate (RMR)), diet history, eating and PA behaviors. Cell phone software will support input of food intake and PA data throughout the day, and periodic interchange between the web program and the cell phone will support at-a-glance updates of the consumer's current EB. To promote a healhier EB, MyBalance will support personalized expert-logic driven text message prompts for improvements in EB behaviors at critical times of the day. The MyBalance website will enable users to track their progress and will provide a data sharing option allowing the user to share selected information with others such as friends or their health care provider. Importantly, MyBalance will be fully developed in both English and Spanish language versions to extend its reach to important populations in need of improved EB.