I’ve struggled with severe to suicidal depression for over a decade and this was a helpful tip from a therapist. 
I hadn’t eaten food or drank any water that day before our virtual session and she told me to go get a glass of water and some to eat while we were talking. She introduced me to Maslow’s Hierarchy of Needs. 
Ultimately, what I can say about this is that if you can address one of two of these primary needs (at the bottom of the period) — if you can! — on a really low day, you are helping yourself and getting your basic needs met.

https://www.thoughtco.com/maslows-hierarchy-of-needs-4582571