Attachment vs legitimate need

I heard a talk by Ajahn Amaro that says that wherever I encounter dukkha, it is a sign that there is an attachment involved, that I can let go of and this way free myself from the dukkha. https://youtu.be/-h_O_SuKOKE?t=2823 But this way, what prevents me from laying down and dying from hunger or thirst - if I feel hunger, it may be dukkha from my attachment to food, or to survival... What is the difference between attachment and legitimate needs? Thanks for answering a noob question.