
zunehmen
to gain weight
To gain body weight; to become heavier.
Ich habe im Urlaub leider drei Kilo zugenommen.
Unfortunately, I gained three kilos while on vacation.
to gain weight / increase
Loading your saved state.

to gain weight
To gain body weight; to become heavier.
Ich habe im Urlaub leider drei Kilo zugenommen.
Unfortunately, I gained three kilos while on vacation.

to increase
To grow in quantity, size, intensity, or strength; to rise.
Die Kriminalität in der Stadt hat in den letzten Jahren stark zugenommen.
Crime in the city has increased sharply in recent years.
'Zunehmen' (to gain weight/increase) is a separable verb. The prefix 'zu-' goes at the end in a main clause. In subordinate clauses and in the infinitive with 'zu', the verb stays together.
Der Wind nimmt am Abend stark zu.
The wind increases strongly in the evening.
The perfect tense of 'zunehmen' (to gain weight/increase) is always formed with the auxiliary verb 'haben' (to have). The past participle is 'zugenommen'.
Die Bevölkerung der Stadt hat im letzten Jahr zugenommen.
The city's population increased last year.
When referring to body weight, 'zunehmen' (to gain weight) is often combined with quantities or the word 'Gewicht' (weight). Typical phrases are 'an Gewicht zunehmen' (to gain weight) or 'ein paar Kilo zunehmen' (to gain a few kilos).
Er hat durch den neuen Job viel an Gewicht zugenommen.
He gained a lot of weight because of the new job.
You can recognize this meaning by the fact that the subject is usually an abstract noun. It describes an increase in something immaterial such as strength, quantity, or intensity.
Die Spannung im Raum nahm spürbar zu.
The tension in the room noticeably increased.
to win / gain
A rise in importance or demand can be described with gewinnen an or zunehmen. With gewinnen an, the quality or value follows an; with zunehmen, the growing quantity itself is the subject. Use both forms according to the sentence structure, without assuming a fixed difference in meaning.

Die Bedeutung des Themas nimmt durch die neuen Zahlen zu.
The importance of the topic is increasing because of the new figures.
Das Thema gewinnt durch die neuen Zahlen an Bedeutung.
The topic is gaining importance because of the new figures.