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.
最近、体重が増えた。
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.
食べすぎて太った。
I ate too much and put on weight.
Formal or written expression for weight increase. Common in medical or academic contexts.
患者の体重が増加した。
The patient put on weight.
To start gaining weight, often over a period. Implies a gradual change.
運動をやめたら太ってきた。
I started putting on weight after I stopped exercising.
To deliberately increase body mass, often muscle.
To intentionally increase body weight. Used for health, sports, or aesthetic goals.
筋肉をつけるために体重を増やしている。
I'm putting on weight to build muscle.
To bulk up or increase mass, often used in fitness contexts.
オフシーズンに増量する選手もいる。
Some athletes put on weight during the off-season.
To gain weight unexpectedly or as a side effect.
Expresses regret or lack of control over weight gain. The 〜てしまう form adds a nuance of unintended result.
ストレスで体重が増えてしまった。
I put on weight due to stress.
Similar to above, but using 太る. Conveys regret about getting fat.
薬の副作用で太ってしまった。
I put on weight as a side effect of the medicine.
The English phrase 'put on weight' cannot be directly translated word-for-word into Japanese. Use the expressions provided instead.
体重を着る（誤り）
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).