This paper presents ongoing work on an adaptive persuasive system to promote healthy eating habits. It exploits and extends the idea of a constrained question answering (QA) system over a knowledge graph proposed by Chen et al. [1]. In particular, we introduce the way to model personalised challenges, a key component of gamified behaviour change techniques, and additional constraints allowing to handle meal plans by keeping a track on the distribution of daily intakes across meals, repetitive recommendations, constraints related to nutritional labels of the recipes. To access rich nutrition and user-item interaction data, we use HUMMUS [2] instead of FoodKG [3].