This paper investigates the impact of large language model (LLM)-based coaching interventions on enhancing physical activity and nutritional habits, following motivational interviewing guidelines. By exploring user perceptions through qualitative research involving eight interviews, five key themes emerged: the tension between the need for authenticity and reservations about AI humanization, the desire for personalized coaching and autonomy, the necessity of simplifying daily tasks, the aspiration for self-development, and the need for perceived privacy and trust. The findings reveal that perceptions of LLM-based coaching are multifaceted and cannot be easily classified as purely beneficial or concerning; they vary based on the specific implementation. This complexity indicates that certain aspects can simultaneously present both benefits and risks. The paper discusses theoretical implications and offers practical recommendations to enhance the advantages and mitigate the risks associated with LLM-based coaching interventions.