The paper introduces ChatDiet, an LLM-powered framework designed for personalized nutrition-oriented food recommendation chatbots. ChatDiet integrates personal and population models, complemented by an orchestrator, to seamlessly retrieve and process relevant information. The personal model uses causal discovery and inference techniques to assess personalized nutritional effects, while the population model provides generalized information on food nutritional content. The orchestrator retrieves, synergizes, and delivers the output of both models to the LLM, providing tailored food recommendations. The framework is evaluated through a case study using data collected over three years from an individual's dietary habits, health metrics, and other relevant information. The evaluation includes a food recommendation test with a 92% effectiveness rate and illustrative dialogue examples demonstrating explainability, personalization, and interactivity. ChatDiet represents a significant step in leveraging technology to improve dietary choices and overall well-being.The paper introduces ChatDiet, an LLM-powered framework designed for personalized nutrition-oriented food recommendation chatbots. ChatDiet integrates personal and population models, complemented by an orchestrator, to seamlessly retrieve and process relevant information. The personal model uses causal discovery and inference techniques to assess personalized nutritional effects, while the population model provides generalized information on food nutritional content. The orchestrator retrieves, synergizes, and delivers the output of both models to the LLM, providing tailored food recommendations. The framework is evaluated through a case study using data collected over three years from an individual's dietary habits, health metrics, and other relevant information. The evaluation includes a food recommendation test with a 92% effectiveness rate and illustrative dialogue examples demonstrating explainability, personalization, and interactivity. ChatDiet represents a significant step in leveraging technology to improve dietary choices and overall well-being.