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Comment by hallqv | Hacker News Reader

Yeeeah, idk how significant this is…

I live in the north of Sweden where we don’t get a lot of sunlight. Not many fat people here compared to other parts of the world where people get a lot more sun exposure.

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Something to consider would be local adaptations the emerged over very long periods of time. Most US residents come from a lineage that is (relatively) very recent to those lands.

Also important to note that the US climate is significantly less homogenous, meaning that a somewhat universally high obesity rate is not going to be explained to a large degree by local climate. IIRC, relative obesity rates drop by roughly 40% for individuals with a college degree and in general correlates highly with socioeconomic factors in the US.

> local adaptations the emerged over very long periods of time

Wisconsin has a lot of fat people of Swedish descent.

People give a lot of thought to why we Americans are fat, but in some cases it's just the incredible beer consumption.

You likely have to look at this like "all else being equal" meaning you can't just say look at obesity rates in US state with lots of sun and look at low obesity rates in this dark country. There are many, many other factors at play.

My work has brought me to live in a few different cities in Europe for a year or so.

You might be trying to compare it to countries with unhealthy eating habits.

Swedish people are definitely a little chunkier, on average, compared to their Mediterranean neighbors. Not FAT, but a little wider. Now there's genetics there, as well as cultural difference, cuisine differences, etc... so any conclusion would need to be tested.

Swedish people are educated, aspire to healthy lifestyle and can afford good food. Article, imho speaks about survival mechanisms which aren't so visible/ so active/useful in times where food and protection from cold are abundant.

Swedish people on avg have a much lighter complexion thus requiring less sun exposure for the same effect

You are already adapted to the climate of Sweden, meaning you have a lighter skin and your body uses sunlight more efficiently, because it's scarce. This is epigenetics in action. This could be problematic for people who originate from a more sunnier climate and have moved closer to the poles in the hemisphere, or to people who don't go outside. Their body expects more sunlight, however they get less, which could trigger more fat storage.

How do we know it's epigenetic? Is there a way to tell?

I think to a certain degree we can adapt to the amount of sunlight at a young age, or even in the womb. Just as we do for food scarcity, see the Dutch winter famine [1]

This article seem to point into the direction of epigenetics. [2]

- [1] https://www.nytimes.com/2018/01/31/science/dutch-famine-gene...

- [2] https://geneticliteracyproject.org/2016/10/17/black-white-tw...

Lack of sunlight is usually also correlated with cold - and being exposed to cold makes you burn fat fast, to maintain your body temperature. Which might be the reason for the finding in the first place.

But the article is proposing the opposite. "Lack of sunlight makes our cells store more fat."

I would say that being in a cold place makes you eat more. And being only sporadically exposed to the cold could somewhat trigger this evolutionary instinct of storing energy without the expected proportional increase on energy expenditure. Long term, fat accumulates.

Hey fellow Swede. The obesity is getting worse though. And during winter people do eat a lot of fatty foods. Almost as if they're compelled to do so.

Notwithstanding, the brightness level outside even in overcast, in lumens, is still much higher than it is indoors. That lack of exposure has a negative impact on the circadian rhythm, mood etc. Exposure to the eyes is more important than exposure to the skin.

My non-scientific interpretation is maybe this has more to do temperature tolerance for individuals than weight gain? Perhaps the sunlight exposure only affects a very small close to surface level of fat and that's it?

Shall I reply with an equally specious counterproof? Colorado versus the rest of the US.

Yep-- Colorado has, on average, lower degrees of poverty and higher levels of education than the national averages. Factors that research indicates are well correlated with obesity. These are more likely factors in their low obesity rates than the direct metabolic impact of local climate.

It local climate has an impact, its somewhat temperate nature probably plays a large part: It has a fair amount of sunshine but doesn't reach the peak temperatures of other high-sunshine states, which probably contributes to the local culture of outdoor activity, and outdoor activities are going to burn more calories.

"It has a fair amount of sunshine but doesn't reach the peak temperatures of other high-sunshine states, which probably contributes to the local culture of outdoor activity, and outdoor activities are going to burn more calories."

It's a simple, true enough fact to make active people move to and live in Colorado, which they do, and which in some part has to impact the overall averages.

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