어/아 지다 works with adjectives to show a changing state:
이번 달 초부터 기온이 올라가졌어요.
Since the start of this month, the temperature has been increasing. (lit. became increased)
나쁜 소식을 들었을 때 술프해졌어요.
I got upset when I heard the bad news.
과식을 하기 때문에 뚱뚱해져요.
I’m becoming overweight because I eat too much.
사람들이 월드컵에 대해 흥분해져요.
People are getting excited about the World Cup.
규칙적으로 식사를 먹으면 더 건강해 질 거에요.
If you eat regular meals you’ll become more healthy.