Body Decoder is an AI-powered mobile-health platform that predicts dietary nutrient deficiencies, excesses, and related health risks from routine food-intake data. Using supervised machine-learning models and explainable-AI techniques, the system classifies each nutrient as Deficient, Normal, or Excess and issues personalised recommendations with clear justifications. A privacy-preserving cloud/edge architecture ingests user logs, curated Indian and international food-composition databases, and optional electronic-health-record feeds to generate real-time guidance for individuals and population-level dashboards for public-health authorities. The hybrid web and native-app clients operate online or offline, enabling reach to rural and underserved communities. By flagging micronutrient gaps early, Body Decoder helps prevent anaemia, osteoporosis, cardiovascular risks, and other diet-related conditions while reducing healthcare costs. The platform aligns with India’s DISHA and PDP regulations and supports integration with school-meal, corporate-wellness, hospital-nutrition, and government nutrition-surveillance programmes.