An illustrative mobile computing device executing weight, nutrition, health, behavior and exercise application software serves as a simulated combination personal trainer and dietician/nutritionist for the user using comprehensive databases storing personalized health, nutrition and exercise information. A mobile computing device, such as a smartphone, executing such software monitors, tracks and/or adjusts caloric intake, energy expenditure taking into account nutritional information and behavioral factors. The mobile computing device receives food consumption, exercise-related, behavior and other input using speech input and the device's GPS subsystem to ease data entry burden on users and to promote continued long-term usage. The system rewards user goal achievement in an automatic, seamless manner, through, for example, downloading music, books, or other media. In illustrative implementations, the system assists users to make healthy food and exercise choices by using a comprehensive color code system to identify good choices, bad choices and those in between.