Translation guide
To become physically larger and heavier, typically by gaining body fat. In Japanese, this is most commonly expressed with the verb 太る (futoru), but other expressions exist for specific nuances like getting a belly, gaining weight in a positive sense, or describing animals.
I'm getting fat.
To gain body fat and become overweight or larger in size.
The standard, neutral verb for gaining weight or becoming fat. Can be used for people and animals.
I've gained weight recently.
Often used for animals becoming fat or plump, or for soil becoming fertile. When used for people, it can sound literary or slightly negative, implying 'fattening up'.
Rare kanji form of 太る, sometimes used in literary contexts. Almost always written as 太る in modern Japanese.
Specifically gaining fat around the stomach area, often used for middle-aged men.
Literally 'stomach comes out', a common colloquial way to say someone has developed a belly.
To put on weight in a healthy or desirable way, without the negative connotation of 'fat'.
Neutral phrase meaning 'body weight increases'. Used in medical or factual contexts.
To become pleasantly plump, often used for babies, children, or in a cute way.
A mimetic word meaning 'to be plump' or 'chubby' in a cute, positive way. Often used for people or animals.
The English phrase 'grow fat' is not directly translated as a single verb in Japanese. The most natural equivalent is 太る (futoru). Using 成長する (seichō suru, 'to grow') plus 太い (futoi, 'fat') would be incorrect.
太る is the everyday word for gaining weight or becoming fat. 肥える is more often used for animals or soil, and can sound literary or negative when applied to people. Stick with 太る for most situations.
If you eat too much, you'll grow fat.
I ate too much and got fat.
この豚はよく肥えている。
This pig is well-fattened.
肥ることは健康に悪い。
Growing fat is bad for your health.
As you reach middle age, you start to get a belly.
Literally 'drum belly', a noun describing a potbelly. Often used humorously.
He's developed quite a potbelly.
I've gained weight since starting exercise.
Transitive verb meaning 'to fatten up' someone or an animal. Can be used in contexts like 'fattening up livestock' or 'making someone gain weight'.
Fatten up the cattle.
The baby is getting chubby.
Literally 'roundly fat', describing someone who is plump and round. Often used for healthy-looking babies or animals.
The puppy is plump and round.
He grew fat after he quit sports.