Mirtazapine 45mg And taking weights loss coffees and juices

i have started taking juices and coffees for weight loss , and on day one today i feel very anxious and am experiencing severe headaches and sickness . Can anyone tell me if this is safe to do together ? Im very much doubting it now but really didnt think until feeling this way today x

Why are coffees and juices going to help you lose weight? Is it safe to do what together?