"Sara comería con sus amigos pero está a régimen de dieta." – what tense is está in here?

I am starting to learn more verb tenses, and I was doing a quiz about the conditional. I filled in comería correctly, but could someone please help me out by letting me know what tense "está" is in this case? I don't think I've learned it/don't recognize it from what I have learned – gracias a todos!