Why Do People Lose Weight in Japan (and Korea) While Eating Whatever They Want?

Callie is our app. It appears near the end, where it fits. Everything else in this article links to its source, and the full list is at the bottom.

The 30-second answer

Most travellers lose weight in Japan because they walk two to five times more than at home. Japan averages 6,010 smartphone-measured steps a day against 4,774 in the US, and a tourist day often runs to 15,000–25,000 steps. For a 70 kg person, 15,000 extra steps burns roughly 440 kcal above resting. Smaller servings and less added fat probably help, but the measured calorie gap is smaller than people think: Japanese adults eat 1,893 kcal a day against 2,036 kcal for US adults. And it usually reverses at home, because the walking stops.

Japan, Korea, Spain and the US in numbers

On every measure that has data, Japan and Korea sit at the walking-heavy, low-obesity end and the US at the other. The gaps are largest for obesity and steps, smaller for daily calories.

Feature	Japan	South Korea	Spain	United States
Average daily steps, smartphone data (Althoff 2017)	6,010	5,755	5,936	4,774
Adult obesity, BMI 30+, WHO 2024 (age-standardised)	5.9%	8.4%	15.3%	41.0%
Measured restaurant meal (Roberts 2018)	Not measured	Not measured	Not measured	1,088 kcal
Adult energy intake, national survey	1,893 kcal (2023, 20+)	1,823 kcal (2022, adults)	About 1,816 kcal (ANIBES 2015, 18–64)	2,036 kcal (2021–2023, 20+)
Share of energy from fat	About 29%	23.4%	38.5%	37%

Two things stand out. Spain walks almost as much as Japan and eats about the same number of calories, yet its obesity rate is more than double, so steps and calories are not the whole story. And the intake column is self-reported and collected differently in each country (a one-day weighed household record in Japan, a 24-hour recall interview in the US), so treat small gaps as noise.

What travellers report on Reddit

The story is common enough to be its own genre: someone spends two weeks in Japan or Korea, eats freely and comes home a few pounds lighter. These posts are first-hand accounts, not evidence, but they show what people notice.

• A poster in r/loseit describes a two-week vacation in Japan where they ate whatever they wanted and still lost weight (December 2023).
• Another spent a month in Korea and Japan and lost weight (May 2024).
• One traveller writing from Korea in April 2026 says the food there makes losing weight far easier.
• r/solotravel has a thread asking which country people lost or gained weight in (February 2024).
• And the reverse: someone back from abroad says they can no longer manage American meal sizes (October 2024).

The explanations people offer come down to walking, portions and what is on the menu. The data below tests each one.

Walking: the biggest single difference

Walking is the best-supported explanation, because both the national step data and the typical tourist day point the same way. In 2017, a Stanford team (first author Tim Althoff) analysed 68 million days of smartphone step data from 717,527 people in 111 countries. In their country data, Hong Kong ranked first of 46 at 6,880 steps a day, Japan fourth at 6,010, and the US 30th at 4,774. Japan's own 2023 national survey, using pedometers, found adult men averaging 6,628 steps and women 5,659. An older US pedometer study put American adults at 5,117 steps in 2003, fewer than adults in Japan, Switzerland or Australia.

The study also tied walking to city design. "In cities that are more walkable everyone tends to take more daily steps, whether male or female, young or old, healthy weight or obese," said Jennifer Hicks, a member of the Stanford team, in the university's release.

Tourists walk far more than residents. Train stations with long transfers, temples, shopping streets and few taxis add up. We estimate a typical sightseeing day at 15,000–25,000 steps; that is our estimate, not a measured figure, so check your own phone's history.

How many calories those steps burn

At 70 kg, every 10,000 extra steps burns roughly 290 kcal above what you would burn sitting. Here is the working. The 2024 Adult Compendium of Physical Activities rates "walking with a day pack, level ground, assumed in the city" at 3.5 METs. A cadence of 100 steps a minute marks moderate intensity (3 METs) in adults aged 21–40, according to the CADENCE-Adults study, so 10,000 steps takes about 100 minutes. The extra burn is (3.5 − 1) × 70 kg × 1.67 hours, or about 290 kcal. At 90 kg it is about 375 kcal.

Our calculation from the Compendium MET value; real burns vary by 20–30% between people. Over a 14-day trip, 15,000 extra steps a day adds up to about 6,000 kcal at 70 kg. One caveat: a 2016 study of 332 adults found that total energy expenditure plateaus at high activity levels as the body adapts, so months of heavy walking burn less than the arithmetic says. Over a two-week trip, the simple sum is closer. You can run your own numbers in our calories burned calculator.

Portion sizes: what is measured and what is not

Large restaurant portions are measured in the US; smaller ones in Japan and Korea are widely reported but not measured the same way. A 2018 BMJ study led by Susan Roberts at Tufts measured 223 restaurant meals in Brazil, China, Finland, Ghana and India by bomb calorimetry. Only China came in lower than the US: 719 kcal per meal against 1,088 kcal. Across the five countries, 94% of full-service meals and 72% of fast-food meals contained at least 600 kcal.

"Current average portion sizes are high in relation to calorie requirements and recommendations globally," Roberts said in the Tufts release.

We found no comparable measurement of Japanese or Korean restaurant meals. The nearest European evidence is a 2003 study by Paul Rozin and colleagues that found smaller portions in comparable restaurants in Paris than in Philadelphia, as well as in cookbooks and supermarket single servings.

The national surveys suggest the daily gap is modest. Japanese adults ate 1,893 kcal a day in 2023 (men 2,108, women 1,703). US adults ate 2,036 kcal (men 2,330, women 1,760). That is about 7%, smaller than many travellers expect. Self-reported surveys undercount, and the two countries collect data differently, so the real gap could be larger or smaller.

What is on the plate

The bigger difference may be what the calories are made of: less added fat and more rice, fish, soup and vegetables. In Japan's 2023 survey, adults got about 29% of their energy from fat, by our calculation from the survey's 61.0 g of fat and 1,893 kcal. US adults got 37%. Korean adults were at 23.4% in 2022, up from 19.0% in 2013–2015, according to an analysis of the Korean national survey.

Japanese adults ate 412.5 g of grains (mostly rice), 62.6 g of fish and 105.3 g of meat a day, with 12.2 g of added oils and fats. Fat is the most calorie-dense nutrient at 9 kcal per gram, and it is the part of a meal that is easiest to miss. We cover why in hidden calories in oil, butter and sauces.

Avoid the stereotype, though. Japanese adults averaged 256.0 g of vegetables a day, and only 25.2% of men and 21.9% of women reached the national 350 g target. By Japan's own obesity cut-off of BMI 25, 31.5% of men and 21.1% of women count as obese. The Japanese diet is not a diet plan; it is a food environment with different defaults.

Not everything is light: konbini and ramen

Convenience stores and ramen shops can deliver a full day's calories in one meal. In May 2026, Unseen Japan reported on a 7-Eleven "G-kei" ramen sold as a single serving: 1,595 kcal and 16.5 g of salt, more than twice Japan's 7.5 g daily salt goal for men. On the kalori.jp listing for 7-Eleven, updated October 19, 2026, a large pork ramen is 986 kcal, a pork cutlet bento 860 kcal and a teriyaki chicken bento 745 kcal.

The same shelves hold the light end: a salted onigiri at 173 kcal, a tuna-mayo onigiri at 227 kcal and salad chicken at 109–117 kcal. Konbini labels list calories under エネルギー (energy), so you can read the number even without reading Japanese.

Salty meals also hold water. If you eat a lot of ramen and miso soup, the scale can read higher the next morning while your fat mass has not changed, which is one reason travel weigh-ins are unreliable in both directions.

Stress, sleep and novelty

Lower stress and a change of routine may play a small part, but the evidence is thin and some of it points the other way. In the 2016 vacation study by Jamie Cooper and T. Tokar, perceived stress scores fell from 17.1 before the trip to 14.9 six weeks after. That did not stop the group gaining weight.

Sleep cuts against travellers. Jet lag and early starts often shorten sleep, and a 2017 meta-analysis of 11 studies found that partial sleep deprivation raised energy intake by 385 kcal a day with no change in energy burned. If you lose weight in Japan despite jet lag, that makes the walking effect look larger, not smaller.

Why it often reverses at home

On average, people gain weight on vacation, and the Japan stories are the exception that walking explains. Cooper and Tokar followed 122 adults through a 1–3 week vacation. Weight rose by 0.32 kg on average and, six weeks later, the total gain was 0.41 kg. Physical activity tended to rise during the trip and then fell significantly afterwards, from 4,313 to 3,715 on the questionnaire's MET scale. The authors wrote: "The weight gain appeared to be driven by increased energy intake above energy requirements." (Physiology & Behavior, 2016)

Back home, the step count falls back to about 4,774 in the US, and restaurant meals average 1,088 kcal again. Part of what you lost was also water and gut content, which comes back within days. If the scale jumps after a trip, our guide to weight gain after vacation explains how much of it is fat.

How to bring it home

You can't bring the train system home, but you can copy the two habits that matter most: more steps and smaller default portions.

1. Set a step target from your trip. Check your phone's step history for the trip and for a normal week at home. Japan's national health plan targets an average of 7,100 steps a day, and the gap between your home number and your trip number is the calorie budget you lost.
2. Walk where you would have driven. Short errands, a station further away, a walk after dinner. Three 15-minute walks are about 4,500 steps.
3. Order like a set meal. A bowl of rice, a palm-sized piece of protein, a soup and a side of vegetables is close to a Japanese teishoku, and it is easier to keep well under the 1,088 kcal average measured for a US restaurant meal.
4. Share or box half of restaurant meals. With measured US meals averaging 1,088 kcal, half is about 540 kcal.
5. Watch the added fat, not the rice. Cooking oil, dressings and fried sides are where most hidden calories sit.
6. Drink tea or water by default. Sweet drinks are easy to cut and easy to forget.

If you would rather change food than add exercise, our guide to losing weight without exercise covers the diet side.

Logging food you can't read

If you want to keep a rough log in Japan or Korea, photo logging with a review step handles unfamiliar dishes better than searching a database. You often don't know the dish's name, let alone its entry in a food database. Our pillar guide on how to track calories while travelling covers the wider approach.

Callie: AI Calorie Tracker is available in six languages, including Japanese. When you photograph a meal, Callie shows its estimate on a review screen before anything is logged, so you can add the oil, change the portion or correct a dish it misread. The AI coach answers in any language, so you can ask about a menu item in English while the menu is in Japanese or Korean. After 3 free AI logs it costs $34.99 a year.

When skipping the tracker is the better choice

For a short trip, not tracking at all is often the better plan. If you are walking 15,000 steps a day and eating normal meals, you are probably near maintenance or below it, and the trip is a break worth taking. Use the scale when you are home, a few days after you land, to see where you really are.

If you want something more structured, MacroFactor is also available in Japanese and English, and Cronometer is the stronger pick if you care about micronutrients such as iron or calcium, which Callie does not track. If tracking food has ever made you anxious, leave the app at home.

Related reading

• How to track calories while travelling, the full travel guide.
• Weight gain after vacation, on how much of the post-trip jump is fat.
• Calories burned calculator, to estimate your own walking burn.
• How to lose weight without exercise, for the food side.
• Hidden calories in oil, butter and sauces, on the fat that photos and menus hide.

Sources

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