How to Say I'm on a Diet in Japanese: Daietto-chū and Polite Refusals

To say I'm on a diet in Japanese, say daietto-chū desu (ダイエット中です). In Japanese, daietto almost always means trying to lose weight. For cutting back on something, use hikaete imasu (控えています), and to decline food kindly, say ato de itadakimasu (I'll have it later) or chotto dake itadakimasu (just a little).

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How to Say I'm on a Diet in Japanese: Daietto-chū and Polite Refusals

Food is shared generously in Japan: omiyage sweets on every desk after a holiday, refills pressed on you at a friend's house, a second bowl of rice from a host who wants you well fed. If you are trying to eat less, you need to say so without making the giver feel rejected. Japanese has a handy loanword, daietto, but it does not mean quite what English diet means, and some ways of declining food sound colder than learners expect. This guide covers the words for dieting, cutting back and low-carb eating, the polite ways to accept a little or save something for later, and the comments about weight you may hear and how to answer them. It ends with a coworker offering omiyage.

Daietto means losing weight; shokuseikatsu means your diet in general

Hikaete imasu, I'm cutting back, is gentle and widely understood

Ato de itadakimasu and chotto dake decline without rejecting

Answer weight comments lightly; you do not have to explain more

Four phrases for eating less

Most conversations about dieting in Japanese use a handful of phrases. Daietto-chū says you are on a diet. Tōshitsu seigen names a low-carb diet. Hikaeru, to hold back, says you are cutting down on something. Chotto dake itadakimasu lets you join in with a small portion.

Four picture cards: I'm on a diet, a low-carb diet, I'm cutting back on sweets, and I'll just have a little.
Saying you are dieting, naming the diet, cutting back, and joining in with a small portion.
JapaneseRomajiMeaning
ダイエット中です。Daietto-chū desu.I'm on a diet.
糖質制限tōshitsu seigena low-carb diet
甘いものは控えてて。Amai mono wa hikaetete.I'm cutting back on sweets.
ちょっとだけいただきます。Chotto dake itadakimasu.I'll just have a little.

Chū is the same suffix you see in benkyō-chū, studying, and kaigi-chū, in a meeting. It marks a state you are in the middle of, so daietto-chū suggests a temporary effort, which makes it easy and light to say.

What daietto really means

The loanword daietto means trying to lose weight. It covers eating less and exercising, so jogging for weight loss is also daietto. It does not mean the food you normally eat. My diet is mostly vegetables is shokuseikatsu wa yasai ga ōi desu, not daietto.

Ashita kara daietto, I'll start the diet tomorrow, is a classic joke said while reaching for dessert.

JapaneseRomajiMeaning
夏までに痩せたいんです。Natsu made ni yasetai n desu.I want to lose weight by summer.
健康のために、食生活に気をつけています。Kenkō no tame ni, shokuseikatsu ni ki o tsukete imasu.I'm careful about my diet for my health.
明日からダイエット！Ashita kara daietto!The diet starts tomorrow! (joking)
EnglishJapaneseNote
I'm on a diet (to lose weight)Daietto-chūThe everyday phrase
My diet, what I usually eatShokuseikatsuEating habits
Medical diet, restrictionsShokuji seigenDoctor's orders
Low-carb dietTōshitsu seigenVery common term

Yaseru, to lose weight, and futoru, to gain weight, are the core verbs. They describe a change, so I've lost weight is yaseta, and someone who is slim is yasete iru.

Cutting back: hikaeru and ki o tsukeru

Hikaeru means to hold back or refrain, and hikaete imasu is a soft, adult way to say I'm cutting down. It works for sugar, alcohol, rice at night or salt, and it does not invite questions about your weight. Ki o tsukete imasu, I'm being careful, is even vaguer and politer. Nuku, to skip, is for cutting something out completely.

JapaneseRomajiMeaning
お酒は控えています。Osake wa hikaete imasu.I'm cutting back on alcohol.
夜は炭水化物を抜いています。Yoru wa tansuikabutsu o nuite imasu.I skip carbs in the evening.
食べすぎに気をつけてるんだ。Tabesugi ni ki o tsuketeru n da.I'm trying not to overeat.
最近ジムに通ってます。Saikin jimu ni kayottemasu.I've been going to the gym lately.

Many set-meal restaurants will happily serve less rice if you ask. Gohan sukuname de, less rice, please, is a useful line, and some places offer extra rice for free, so it is worth saying before the bowl arrives.

Declining food without rejecting the giver

When someone offers food, the offer is about kindness, so the answer should honour the kindness first. Thank them, then choose: a little now, save it for later, or a polite full refusal. Kekkō desu, no thank you, is correct but can sound brisk on its own; with a thank you and a softer phrase it is fine.

JapaneseRomajiMeaning
ありがとうございます。後でいただきます。Arigatō gozaimasu. Ato de itadakimasu.Thank you. I'll have it later.
持って帰ってもいいですか。Motte kaette mo ii desu ka.May I take it home?
お気持ちだけいただきます。Okimochi dake itadakimasu.I'll accept just the kind thought.
もうお腹いっぱいです。Mō onaka ippai desu.I'm already full.
おいしかったです。ごちそうさまでした。Oishikatta desu. Gochisōsama deshita.It was delicious. Thank you for the meal.

At a home meal, the host may offer more than once, and a second warm refusal is normal and usually accepted. Mō jūbun itadakimashita, I've had plenty, with a smile closes the topic.

When people comment on your weight

Comments such as yaseta? (have you lost weight?) or even futotta? (have you put on weight?) can come up between friends and family more directly than many English speakers expect, though plenty of people find them rude too. You do not owe an explanation. A light answer moves the conversation on.

For your own body, futotchatta, I've put on weight, said with a smile, is the usual self-deprecating line. Avoid commenting on other people's weight yourself unless they raise it.

JapaneseRomajiMeaning
ちょっと太っちゃった。Chotto futotchatta.I've put on a little weight.
ありがとう、少し痩せました。Arigatō, sukoshi yasemashita.Thanks, I've lost a bit of weight.
そうかな？元気だよ。Sō ka na? Genki da yo.Do you think so? I'm doing well.

If a comment stings, it is fine to change the subject. Sore yori, anyway, followed by a new topic, is a gentle way to steer away without making a scene.

A spoken exchange: omiyage at the office

A coworker is back from Hokkaido and going from desk to desk with a box of sweets. You are cutting back, but you do not want to be the only person who refuses.

A middle-aged man at his office desk laughing as he takes one small wrapped sweet from a box held out by a smiling coworker
Thank first, then a little or later: the graceful way to handle omiyage on a diet.
JapaneseRomajiMeaning
北海道のお土産です。よかったらどうぞ。Hokkaidō no omiyage desu. Yokattara dōzo.Coworker: Souvenirs from Hokkaido. Please have one.
わあ、ありがとうございます。Wā, arigatō gozaimasu.You: Oh, thank you.
今ダイエット中なので、後でいただきますね。Ima daietto-chū na node, ato de itadakimasu ne.You: I'm on a diet, so I'll have it later.
そうなんだ。一つだけでも？Sō nan da. Hitotsu dake demo?Coworker: I see. Not even one?
じゃあ、ちょっとだけいただきます。Jā, chotto dake itadakimasu.You: All right, I'll have just a little.
おいしい！やっぱり我慢できませんね。Oishii! Yappari gaman dekimasen ne.You: Delicious! I knew I couldn't resist.

Yappari, as expected, makes giving in sound charming. Plenty of conversations about diets in Japan end exactly like this, with a small bite and a shared laugh.

Exercise and health check talk

Conversations about diets often turn to exercise and health checks. Many companies in Japan hold an annual health check, kenkō shindan, and the results are a common, slightly rueful topic among coworkers. Undō busoku, not enough exercise, is the classic confession, and kintore, strength training, is a popular hobby to mention.

Saying what you do is a friendly way to move the conversation away from food: saikin hashittemasu, I've been running lately, invites questions instead of another sweet. If a coworker mentions their own diet, support is the usual reply rather than advice: ganbatte kudasai, good luck, or otagai ganbarimashō, let's both keep at it.

JapaneseRomajiMeaning
健康診断の結果が気になります。Kenkō shindan no kekka ga ki ni narimasu.I'm worried about my health check results.
最近、走ってます。Saikin, hashittemasu.I've been running lately.
週に二回、筋トレをしています。Shū ni nikai, kintore o shite imasu.I do strength training twice a week.
運動不足なんです。Undō busoku nan desu.I don't get enough exercise.
お互い頑張りましょう。Otagai ganbarimashō.Let's both keep at it.

Common mistakes

  • Using daietto for your usual eating. Say shokuseikatsu.
  • Answering an offer with a bare iranai. Thank the person and add ato de or chotto dake.
  • Giving a diet excuse for an allergy. Say the real reason so nobody serves it to you by mistake.
  • Telling a host the food is too much. Mō onaka ippai desu, I'm full, keeps the compliment intact.

Whatever you choose, the thank you comes first. A refusal wrapped in gratitude rarely offends anyone.

Key points

A practical way to improve

Make the refusals automatic. First, say what you are cutting back on with the pattern X wa hikaete imasu for three foods you really do eat less of. Second, practise three graceful responses to an offer: ato de itadakimasu, chotto dake itadakimasu, and okimochi dake itadakimasu. Third, in Unihongo's 3D classroom, ask your AI Sensei to play a coworker handing round omiyage sweets, and then a friend's mother offering you a third helping. Decline or accept a little each time, always with a thank you and a compliment. Ask the Sensei to switch between casual and polite so you hear both versions, and check the session report for any refusal that sounded too blunt.

  1. 1

    Choose one clear goal

    Focus each session on a situation or skill you can actually use.

  2. 2

    Practice actively

    Say complete answers aloud instead of only reading or recognizing Japanese.

  3. 3

    Review and repeat

    Keep useful corrections and revisit the same skill until it feels natural.

FAQ

Frequently asked questions

How do you say I'm on a diet in Japanese?

Daietto-chū desu (ダイエット中です), or casually daietto-chū nan da. Chū means in the middle of, so the phrase is literally in the middle of a diet. People often add a smile, because it is a common, slightly self-mocking topic.

Does daietto mean diet in Japanese?

Mostly it means losing weight, through eating less or through exercise. For your diet in the sense of what you usually eat, say shokuseikatsu (食生活) or shokuji (食事). A medically restricted diet is shokuji seigen (食事制限).

How do I politely refuse food in Japan?

Thank the person, then accept a little or save it for later: arigatō gozaimasu, ato de itadakimasu, or chotto dake itadakimasu. Okimochi dake itadakimasu, I'll accept just the kind thought, is a very polite full refusal. For allergies or religious rules, be direct and give the reason.

How do you say low-carb in Japanese?

Tōshitsu seigen (糖質制限), literally sugar restriction, is the usual term for a low-carb diet. Many restaurants and convenience stores label low-carb products with tōshitsu ofu (糖質オフ) or similar wording.

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