In 15 Seconds
- Used specifically for the act of trying to lose weight.
- Combines the English loanword 'diet' with the Japanese verb 'to do'.
- Commonly used as a polite reason to decline high-calorie food.
Meaning
This phrase means you are actively trying to lose weight or improve your health through food and exercise. It is the most common way to tell someone you are 'on a diet' in Japanese.
Key Examples
3 of 6Declining a dessert at a party
すみません、今ダイエットをしているので、ケーキは遠慮しておきます。
I'm sorry, I'm on a diet right now, so I'll pass on the cake.
Talking about New Year's resolutions
来年から絶対にダイエットをするぞ！
I'm definitely going on a diet starting next year!
A doctor giving advice to a patient
健康のために、少しダイエットをしましょう。
Let's go on a bit of a diet for your health.
Cultural Background
In Japan, 'diet' almost exclusively refers to weight loss rather than general nutrition. The term became popular during the post-war era as Western beauty standards influenced Japanese society. Today, it is a multi-billion yen industry reflected in endless TV specials and 'diet' menus at restaurants.
The 'Diet-chu' Shortcut
If you want to sound like a local, just say `ダイエット中` (diet-chu). It literally means 'in the middle of a diet' and is much faster to say when someone offers you food.
Don't 'Diet' Others
Never tell someone else `ダイエットをしたほうがいい` (You should go on a diet). In Japan, even though people are thin, comments about weight are very sensitive and can be hurtful.
In 15 Seconds
- Used specifically for the act of trying to lose weight.
- Combines the English loanword 'diet' with the Japanese verb 'to do'.
- Commonly used as a polite reason to decline high-calorie food.
What It Means
ダイエットをする is your go-to phrase for weight loss. In English, 'diet' can just mean the food you eat. In Japanese, it almost always means losing weight. It combines the loanword diet with the verb suru (to do). It is active and intentional. You are not just 'having' a diet; you are 'doing' it.
How To Use It
You use this phrase like any other suru verb. If you are currently dieting, use ダイエットをしています. If you plan to start, use ダイエットをするつもりです. It is very flexible. You can use it with friends or even your doctor. It sounds natural in almost any conversation about health. Just remember that it focuses on the action of slimming down.
When To Use It
Use it when someone offers you a delicious donut. It is a perfect polite excuse to decline sweets. Use it when chatting about New Year's resolutions. You might also use it when talking to a trainer. It fits perfectly in a text message to a friend. 'I'm starting my diet today!' is a classic Monday morning text.
When NOT To Use It
Avoid using this if you are just eating healthy. If you aren't trying to lose weight, use 健康的な食事 instead. Do not say it to someone else as a suggestion. Telling a friend ダイエットをしたら？ is a quick way to lose friends. It can be a sensitive topic for some people. Keep the focus on your own journey. Also, do not use it for medical 'diets' like low-sodium. For those, use the word 食事療法 (dietary therapy).
Cultural Background
Japan has a very strong culture of staying slim. There is even a law called the 'Metabo Law.' It encourages companies to monitor employees' waistlines. Because of this, ダイエット is a constant topic of conversation. You will see 'diet' products in every single convenience store. It is often seen as a sign of self-discipline. However, the 'start tomorrow' joke is just as popular in Japan. Everyone relates to the struggle of resisting ramen at midnight.
Common Variations
You will often hear ダイエット中 (diet-chu). This means 'currently in the middle of a diet.' It is very punchy and common in casual speech. Another one is 糖質制限 (toshitsu seigen), which means low-carb. If you are doing a specific diet, you might mention that. But ダイエットをする remains the king of general weight loss phrases.
Usage Notes
This phrase is neutral and safe for most conversations. Use the '~te imasu' form for current status and '~suru' for future plans.
The 'Diet-chu' Shortcut
If you want to sound like a local, just say `ダイエット中` (diet-chu). It literally means 'in the middle of a diet' and is much faster to say when someone offers you food.
Don't 'Diet' Others
Never tell someone else `ダイエットをしたほうがいい` (You should go on a diet). In Japan, even though people are thin, comments about weight are very sensitive and can be hurtful.
It's Not Just Food
In Japanese, `ダイエットをする` often implies both eating less AND exercising. If you only mean exercise, use `運動する` (undou suru).
Examples
6すみません、今ダイエットをしているので、ケーキは遠慮しておきます。
I'm sorry, I'm on a diet right now, so I'll pass on the cake.
Using the continuous form 'shite-iru' shows it is an ongoing effort.
来年から絶対にダイエットをするぞ！
I'm definitely going on a diet starting next year!
The 'zo' ending adds a masculine, determined punch to the resolution.
健康のために、少しダイエットをしましょう。
Let's go on a bit of a diet for your health.
The 'mashou' ending makes the suggestion sound collaborative and professional.
今日からダイエットすることにした。一緒に頑張ろう！
I decided to go on a diet starting today. Let's do our best together!
A common way to seek an accountability partner via text.
明日からダイエットをするから、今日は最後にラーメンを食べよう。
I'll start my diet tomorrow, so let's have one last ramen today.
The classic 'diet starts tomorrow' joke used globally.
一ヶ月もダイエットをしているのに、全然痩せないんだ。
I've been dieting for a month, but I'm not losing weight at all.
Shows the struggle and emotional weight of the process.
Test Yourself
Choose the correct verb form to say 'I am currently on a diet.'
私は今、___。
The '~te imasu' form indicates an ongoing action or state, which is necessary for 'being on a diet'.
Complete the sentence to say 'I will start a diet tomorrow.'
明日から___。
The dictionary form 'suru' is used for future intentions or habits.
🎉 Score: /2
Visual Learning Aids
Formality of 'Dieting' Expressions
Used with close friends or family.
ダイエット中 (Diet-chu)
Standard way to say it in most situations.
ダイエットをする (Diet o suru)
Used in medical or professional settings.
ダイエットに励む (Diet ni hagemu - to strive at a diet)
When to say 'Diet o suru'
At a bakery
Declining a sample
At the gym
Explaining your goal to a trainer
New Year's Day
Setting a resolution
With friends
Explaining why you're drinking water
Practice Bank
2 exercises私は今、___。
The '~te imasu' form indicates an ongoing action or state, which is necessary for 'being on a diet'.
明日から___。
The dictionary form 'suru' is used for future intentions or habits.
🎉 Score: /2
Frequently Asked Questions
10 questionsNot exactly. In English, it can mean your general food intake. In Japanese, ダイエット specifically means trying to lose weight.
Yes, if you use the polite form ダイエットをしています. It is a neutral topic, though some might find it a bit personal for the office.
Usually, no. For medical reasons like diabetes, use 食事制限 (shokuji seigen - dietary restriction) or 食事療法 (shokuji ryouhou).
ダイエットをする is the action/process of trying. 痩せる (yaseru) is the result of actually becoming thin.
You would say ケトジェニックダイエットをしています. You just add the specific type before the word ダイエット.
It is very common! Japanese people often discuss their diet while actually eating a large meal, usually as a joke or a sign of guilt.
It is a casual way to say 'I am currently dieting.' The chu (中) means 'currently in progress'.
Absolutely. It is gender-neutral. Men might use it more often when talking about their 'metabo' (metabolic syndrome) checkups.
Yes, 減量 (genryou) is a more technical or formal term often used by athletes or in medical contexts.
Using it to mean 'I am eating food.' If you want to say 'My diet consists of rice,' use 食生活 (shokuseikatsu) instead.
Related Phrases
痩せる
to lose weight / to get thin
リバウンドする
to regain weight (rebound)
食事制限
dietary restrictions
ジムに通う
to go to the gym
