how would you say i gained weight in french

You’d say “J’ai pris du poids” in French. It means “I gained weight.”

A few useful variants:

• J’ai pris du poids = I gained weight.

• Je prends du poids = I’m gaining weight.

• Une prise de poids = weight gain.

If you want a more neutral or softer phrasing, “j’ai pris un peu de poids” works well.