变胖

Both 变胖 (biànpàng) and 发胖 (fāpàng) mean 'to gain weight' or 'to get fat.' They are largely interchangeable in everyday conversation. Sometimes 发胖 can imply a more gradual or noticeable process of gaining weight, but for most situations, you can use either.

No, 变胖 is specifically used for living beings (people, animals) gaining weight. For an object getting bigger or swelling, you'd use a different word, like 变大 (biàndà - to get big) or 膨胀 (péngzhàng - to swell).

It can be seen as negative, especially in contexts where people are concerned about their health or appearance. However, it's a neutral descriptive term. It literally means 'to become fat.' The implication depends on the context and the speaker's tone. If you want to say someone gained weight in a more neutral or even positive way (e.g., a baby growing), you might say 长胖了 (zhǎngpàng le), which means 'to grow fat' or 'to put on weight' and often has a connotation of healthy growth.

You would say: 我不想变胖 (wǒ bù xiǎng biànpàng).

The opposite of 变胖 is 变瘦 (biànshòu), which means 'to lose weight' or 'to get thin.'

Yes, you can, but the nuance is important. If you want to convey a positive change, it's often better to say 长胖了 (zhǎngpàng le). For example, if someone was underweight and is now healthier, you might say: 他长胖了一点，看起来更健康了 (Tā zhǎngpàng le yīdiǎn, kànqǐlái gèng jiànkāng le). (He gained a little weight, looks healthier.) Using 变胖 might sound a bit blunt, but it's not incorrect in a descriptive sense.

A direct translation like '你变胖了吗?' (Nǐ biànpàng le ma?) might be considered impolite. A more tactful way to ask about someone's appearance or health that might hint at weight gain is to say something like: 你最近看起来气色很好！(Nǐ zuìjìn kànqǐlái qìsè hěn hǎo!) (You look very well recently!) or 你是不是吃得很好啊？(Nǐ shì bu shì chī de hěn hǎo a?) (Are you eating very well?). However, it's generally best to avoid commenting on someone's weight unless you have a very close relationship and know it won't offend them.

While 变胖 is a straightforward term, a common phrase associated with it is 心宽体胖 (xīnlkuān tǐpàng), which means 'a broad mind and a plump body.' It suggests that someone who is optimistic and unworried tends to be well-fed and maybe a bit chubby. It's often used humorously or affectionately.

You could say: 我最近吃太多了，开始变胖了 (Wǒ zuìjìn chī tài duō le, kāishǐ biànpàng le). (I've been eating too much recently, I've started to gain weight.)

变胖 is a very common and natural way to say 'to gain weight.' It's neither particularly formal nor informal; it's suitable for most everyday conversations.