Translation guide
To gain body weight, either intentionally or unintentionally. Japanese expressions vary by formality, cause, and nuance.
To become heavier in body weight, in a neutral or everyday sense.
Neutral and common way to say body weight increases. Suitable for most situations.
I've put on weight recently.
To get fat or gain weight, often with a nuance of becoming plump. Can be blunt, so use with care.
Can sound direct or rude if used about others. For polite contexts, use 体重が増える or euphemisms.
I ate too much and put on weight.
Formal or written expression for weight increase. Common in medical or academic contexts.
The patient put on weight.
To start gaining weight, often over a period. Implies a gradual change.
I started putting on weight after I stopped exercising.
To deliberately increase body mass, often muscle.
To gain weight unexpectedly or as a side effect.
The English phrase 'put on weight' cannot be directly translated word-for-word into Japanese. Use the expressions provided instead.
put on weight (incorrect literal translation)
太る often implies becoming visibly fatter, while 体重が増える is a neutral statement about weight increase. Use 体重が増える in formal or medical contexts, and 太る in casual conversation (but be mindful of politeness).