Look around any town and you'll spot plenty of guys in their 40s and 50s with a proper beer belly. But once you get to men in their 70s and 80s, the ones who make you think "wow, that's a big guy" seem to almost vanish.
You're not imagining it. Not completely, anyway.
But the quick answer people reach for, "heavy people just die before they get old," is way too simple.
Japan's latest national health survey tells a more interesting story.
1. The short version: "a bit heavy" sticks around, "very big" gets rare
In Japan's 2024 National Health and Nutrition Survey, the share of men with a BMI of 25 or more (overweight or above) was 35.8% in their 40s, 38.3% in their 50s, 33.6% in their 60s, and 29.4% at 70 and older.[1][2]
So about 3 in 10 men over 70 are still in the overweight range.
Heavier older men have clearly not gone extinct.
Now look only at BMI 30 or more (the obesity range), and the picture changes:
- 40s: 7.7%
- 50s: 7.2%
- 60s: 3.5%
- 70 and older: 2.4%
- 70–74: 3.0%
- 75–79: 2.5%
- 80–84: 2.3%
- 85 and older: 0.7%
That's roughly 1 in 14 men in their 50s, about 1 in 42 men over 70, and about 1 in 140 men aged 85 and up.
Of course, you can't read someone's BMI by looking at them on the street. Still, the group most likely to strike you as "really big" does get much smaller, and the national data backs that up.
Think of it like a video game: the slightly chubby grandpas in the background are still there, but the boss-sized characters who fill the whole screen show up a lot less.
2. Older men weigh less on average, too
In the same 2024 survey, the average weight of men was 70.9 kg in their 50s, 68.1 kg in their 60s, 63.3 kg at 70 and older, and 60.5 kg at 80 and older. Average BMI was 24.4 in the 50s, 23.9 in the 60s, 23.4 at 70-plus, and 22.7 at 85-plus.[2]
But here's the important catch.
This does not mean the same man weighed 70.9 kg at 50 and then shrank by age 85.
It's a snapshot: different age groups, measured at the same time.
It's like looking at a family photo and assuming the guy in his 50s on the left will turn into the 85-year-old on the right in 30 years. That's not how it works.
Changes from aging and differences between generations are mixed together.
3. So why do big older men seem to disappear?
There isn't one reason. At least 5 things are going on at the same time.
3-1. Yes, some heavier people do die earlier
High BMI is linked to a higher risk of heart disease and other illnesses, though how strong that link is depends on age and sex. A study that pooled several large Japanese groups found a higher overall death rate at BMI 30–40 than in the reference group (BMI 23–25).[3]
So it's fair to say that who makes it to old age is partly filtered.
But that doesn't mean "heavy people mostly die before 70."
The JACC study, which followed Japanese adults aged 65–79, found a clearly higher death risk at low BMI, and the lowest overall death risk across a wide range, BMI 20–29.9.[4]
For older people, BMI isn't a game where "the thinner you are, the more you win."
3-2. Some people lose weight as they get older
It's not just age itself. Illness, poor appetite, trouble swallowing, dental problems, medications, loneliness and moving around less can all make people lose weight.
A meta-analysis of studies on older adults found that losing weight was linked to a higher death risk compared with keeping a stable weight.[5]
So if you see an 80-year-old who has gotten thin, don't automatically think, "Nice, he slimmed down and got healthier."
In old age, weight loss you didn't plan can be a warning light, not a victory screen.
3-3. Losing muscle changes how big someone looks
Muscle and strength tend to drop as we age.
When someone has a lot of body fat but also less muscle or weaker muscles, it's called sarcopenic obesity. ESPEN and EASO, two European clinical nutrition and obesity groups, have proposed an international definition and a way to diagnose it.[6]
This is where your eyes get fooled.
Even if the fat is still there, once the shoulders, chest and legs lose muscle, the body no longer looks as "massive" as it did when the person was younger.
It's not just the number on the scale. What the body is made of changes.
3-4. Different generations, different bodies
Today's 85-year-olds and today's 50-year-olds didn't grow up eating the same food in the same world.
A study of Japan's national surveys from 1973 to 2016 found that overweight and obesity among older men rose a lot over the long run, with clear differences depending on when people were born.[7]
So you can't take the people in their 50s in 2026 and just paste them onto today's 80-somethings.
People in their 80s 30 years from now may have quite different body sizes from the 80-year-olds we see today.
3-5. The old people you see out and about aren't all old people
This one is less about statistics and more about where you're looking.
The older people you see on the street, at the supermarket, at the station or in restaurants are mostly the ones who can still get out on their own.
People who have trouble moving, are in the hospital, live in care homes or mostly stay at home don't show up in your "street sample."
Your eyes are not a national census.
Seeing 100 people outside a train station doesn't tell you what all of Japan's men in their 70s and 80s look like.
4. "No fat grandpas means they all died" is half the answer pretending to be the whole thing
Death does play a part.
But in reality, these all stack up at once:
people dying earlier
- weight loss in old age
- muscle loss
- generation differences
- who you can actually see out in public
In video game terms, it's not that every enemy got defeated.
Some left the map. Some changed class and now look different. Some are characters from a different generation of the game. Some are just staying indoors and never spawn in the field.
Putting all of that under one "died" button is pretty sloppy log analysis.
5. For older people, "heavier" doesn't simply mean "more dangerous"
In older people, a low BMI and losing weight matter a lot too.
A 2025 study of more than 310,000 Japanese people aged 65–74 found that a low BMI and a high ABSI (A Body Shape Index, a measure of belly fat) were each linked to a higher risk of death, and that BMI alone doesn't show the full risk for older adults.[8]
So in later life, it helps to ask separate questions:
"How much fat is there?" "Is the muscle holding up?" "Is the fat mostly around the belly?" "Has there been weight loss lately without trying?" "Is the person eating well?" "Can the person get around?"
BMI is a handy map, but it's not a satellite photo.
6. Your street observation is pretty sharp. It just can't tell you the cause
"After 70, you hardly ever see really huge men."
That impression matches the direction of Japan's 2024 data.
The share of men with BMI 30 or more drops from 7.2% in their 50s to 2.4% at 70-plus and 0.7% at 85-plus, which fits what people notice.[2]
But jumping from
"I don't see them" → "they don't exist" → "they all died"
skips three steps at once.
The observation: correct. The causes: several. The conclusion: don't overhype it.
That's the most accurate way to put it.
7. The most surprising part: plenty of men over 70 are still on the heavy side
It feels like obesity just disappears in old age.
But 29.4% of men aged 70 and older still have a BMI of 25 or more.
What's shrinking isn't the whole "overweight" group.
It's mainly the very visible top end, BMI 30 and up.
That's why you can walk around thinking "there are no fat old guys anywhere," then open the stats and find "actually, plenty of them are overweight." Both are true at the same time.
Our eyes remember the extremes, not the average.
When the really big people become rare, it feels like everyone got thinner.
8. The takeaway
The feeling that you rarely see obviously big men over 70 does have real data behind it.
But the accurate version is this:
Men over 70 with a BMI of 25 or more are not rare. Men with a BMI of 30 or more, though, become much less common. That's not only because of earlier deaths, but also weight loss, muscle loss, generation differences and the fact that you only see people who are out and about.
And for older people, being too thin or losing weight without trying is something you can't ignore either.
What started as a street-corner question, "where did all the big old guys go?", ended in a surprisingly serious conclusion:
In old age, body weight alone tells you very little about what's really going on in the body.
References (8)
- Japan Ministry of Health, Labour and Welfare, 2024 National Health and Nutrition Survey results mhlw.go.jp
- MHLW, 2024 National Health and Nutrition Survey, Part 2: Physical Status mhlw.go.jp
- Sasazuki S, et al. Body mass index and mortality from all causes and major causes in Japanese. J Epidemiol. 2011 pubmed.ncbi.nlm.nih.gov
- Tamakoshi A, et al. BMI and all-cause mortality among Japanese older adults: findings from the Japan Collaborative Cohort Study. Obesity (Silver Spring). 2010 pubmed.ncbi.nlm.nih.gov
- The association of weight change and all-cause mortality in older adults: a systematic review and meta-analysis pubmed.ncbi.nlm.nih.gov
- Donini LM, et al. Definition and diagnostic criteria for sarcopenic obesity: ESPEN and EASO consensus statement. Clin Nutr. 2022 pubmed.ncbi.nlm.nih.gov
- Tarui I, et al. Trends in BMI among elderly Japanese population: findings from 1973 to 2016 Japan National Health and Nutrition Survey. Public Health Nutr. 2020 pubmed.ncbi.nlm.nih.gov
- Kosugi T, et al. Association of body indices with mortality in older population: Japan Specific Health Checkups Study. J Am Geriatr Soc. 2025 pubmed.ncbi.nlm.nih.gov
