About a month ago I put up my first post on this weblog. I argued that South Asians have been genetically undersampled, which is rather alarming considering that Indians, Pakistanis, Bangladeshis, Nepalis, Sri Lankans, etc., are 1/6th of humanity. The alarming part is that understanding population genetic structure is considered a prior condition of much medical genetic research. Without taking into account genetic relatedness one can not usefully establish correlations between particular variants and particular diseases or traits. For example, it is well known that South Asians have a high risk for diabetes, but the possible risk variation within this genetically diverse group has barely been addressed (there is some data which indicate that Bengalis and South Indians are at more risk than Punjabis).
But enough of the dour. In that inaugural post I pointed to the Harappa Ancestry Project, my friend Zack Ajmal’s attempt to catalog undersampled South Asian groups. For political reasons the population of Pakistan has been very well surveyed, but India, especially the Indo-Gangetic plain, far less so. Since then over 50 people have signed up, allowing for the production of many results. Uttar Pradesh, Bihar, and eastern India and Bangladesh are still undersampled. I will also add that I believe Zack is the first person to publish a SNP-chip result from someone of the Nadar community. Since colorful bar plots can confuse, I thought I’d point the readers of this weblog to a 3-D animation Zack produced based on his merged genetic data set.
To the left is a screenshot. You can see it as a 3-D animation at Zack’s site. The image shows the position of individuals in a three dimensional space which corresponds to dimensions of genetic variation found within his South Asian data set. A linear axis illustrates that the largest component of variance goes from Pakistan to southern India and Bangladesh. But the Burusho and a cluster of Gujaratis are deviated from the main axis. For the Burusho that is simply a function of low consistent levels of Tibetan admixture. The Gujaratis break into two groups, one which forms a tight cluster, and one which is distributed across the main axis. I’ve spoken of the tight cluster before. This pattern indicates that the Houston Gujarati population from which these samples were collected has within it a closely related endogamous population, which will tend to shake out in their own cluster in any PCA because they share so much genetic variance. We still haven’t figured out who/what the mysterious Gujarati cluster, but I suspect we will in the near future.
What about Pashtuns and Balochis, are they at greater risk than Punjabis too? I wonder if this difference in Desi groups is due to environmental factors like diet/exercise or purely genetic reasons.
Also, speaking of diabetes, I’ve read online that south asians are at risk for diabetes and related illnesses at a lower BMI than other ethnic groups. For example, this charthttp://www.pamf.org/southasian/risk/concerns/bmi.html (from the Palo Alto Medical foundation, and I’ve seen similar ones online) indicates we become overweight at a BMI of 23 (I believe 25 is the cutoff for other groups). This seems exaggerated to me – going by the chart, your average 5’4″ female would become “overweight” at 134 lbs – that is in no way overweight, I know women about that size who aren’t fat at all. I’m pretty slender myself, and if I gained 10 lbs, I would become overweight according to that chart.
I’m guessing the usual BMI is a horrible way to judge South Asians? It doesn’t take distribution of body fat into account, merely height to weight ratio.
I wonder if this difference in Desi groups is due to environmental factors like diet/exercise or purely genetic reasons.
yeah, that’s what we need to know. i wouldn’t be surprised if it is diet. one thing i’ve read is that in terms of very sweet foods the only cuisine which is as elaborated as the european one is the south asian one. probably because cane sugar is indigenous to south asia? anyway, probably one issue is that as south asians got richer, such as indian immigrants to the west, they ate sweets all the time, instead of on special occasions.
I’m guessing the usual BMI is a horrible way to judge South Asians? It doesn’t take distribution of body fat into account, merely height to weight ratio.
we have more % body fat for the same weight, and it is badly distributed (around the stomach instead of the thighs or ass). i recommend brownz to keep a close watch on their year blood sugar levels, and make radical lifestyle changes if they get into the pre-diabetic range. if you don’t have a sweet tooth, avoid refined sugar when you can. avoid processed food, since they have high carb and sugar loads quite often. work out and build muscle. i assume that the higher bangladeshi rate of diabetes than pakistanis in britain might be due to the fact that we’re a smaller and less robust people?
there are some interesting physiological studies on this issue btw. our mitochondria might be more efficient.
Finally, why generalize about Indians entirely-such as body fat is around waist and not thighs or glutes? What if it has to do with the type of diet eaten that causes this and has nothing to do with genetic predisposition? I know you did not make a connection between genetics and distribution but you seemed to imply it. At the very least you implied that having this distribution is worse than on your thighs or glutes. Perhaps aesthetically but how about healthwise? I know of now direct linkage between the two (other than epidemiologic studies).
I’m not sure what your background is, but I have to comment now…mainly because you seem to write a lot on this forum. This used to be less about genetics and more about cultural and societal issues. Not that theres anything wrong with what your doing but there is a huge issue with the methodology. Merely finding discrepancies in genetic differences between Indian cohort is almost meaningless. No matter how significant the results they dont purport any meaningful information. Even if you find a correlation between genetic markers and a prevalence for some condition theres no reason to believe theyre associated.
That may be one big reason why very little such research has been conducted. What meaning, if any, would it provide? I for one cannot figure it out. Unless the biological mechanism from gene to phenotype has been mapped out, one cannot determine regardless of the type of epidemiologic study done whether the disease or condition is due in any part due to the gene.
This is commonly called the searching for candidate genes-looking for genes with high associations with a particular disease. they are notorious for lack of replication. I would be exceedingly cautious before considering any relationship between this type of data and a disease such as diabetes. The other major issue which you folks touched upon is the environment effect. Yet we dont know whether the gene or environment is responsible for it or the gene-environment interaction is. For example, on its own the gene may not be harmful, and perhaps the environment also may not be a precursor to a particular disease. (I use environment liberally-diet, exercise, whatever). But what about epigenetic effects? Thats something these types of analysis you are looking into offer nothing about.
Just because there is data doesnt mean we should look into it and somehow glean some meaning. Theres a reason why genetic studies today except in some diseases have not panned out all that much.
I’m not sure what your background is, but I have to comment now…mainly because you seem to write a lot on this forum. This used to be less about genetics and more about cultural and societal issues
i have been blogging about genetics since 2002. i have been reading this weblog since 2004, and was friends in “real life” with some of the cofounders of this weblog. how’s that for background? any more meta-comments will be deleted.
This is commonly called the searching for candidate genes-looking for genes with high associations with a particular disease. they are notorious for lack of replication.
well, i don’t know your background, but i was implying GWAS, not candidate-gene. i’m aware of the issues of replication and under-powered studies. instead of giving up, i think we should expand the sample sizes and populations surveyed.
But what about epigenetic effects?
epigenetics is interesting, but i’m pretty sure it’s being over-hyped. i get asked about epigenetics constantly, and i think it has to do with the “wow” “contradicts the ‘central dogma'” factor.
Just because there is data doesnt mean we should look into it and somehow glean some meaning. Theres a reason why genetic studies today except in some diseases have not panned out all that much.
what does this even mean? yes, there’s going to be a lot of false positives. but your assertions are so vague, general, and qualifying that i don’t even know how to respond. the point is that on south asians there isn’t much data. most of the stuff you are alluding to have been on european samples, or perhaps east asian or african ones. we’re not one of the early ‘reference populations.’ though i am becoming convinced that a lot of the risk alleles which have been assumed to be robust are valid across populations.
I know of now direct linkage between the two (other than epidemiologic studies)
i thought this was a robust correlation. i.e., that visceral fat is more deleterious than fatty deposits in other religions. you’re right that most of the stuff i’ve seen is correlational, in which case there should be skepticism a priori. i wonder if anyone could posit a physiological mechanism, or have?
btw, readers might be interested in this, Could mitochondrial efficiency explain the susceptibility to adiposity, metabolic syndrome, diabetes and cardiovascular diseases in South Asian populations?.
I know you did not make a connection between genetics and distribution but you seemed to imply it
and don’t make comments about what i “imply.” i don’t trust in the mind-reading abilities of others. there’s enough i state baldy to actually engage.
Sup dudes. What do South and East Indians have in common? RICE. Link to diabetes? Perhaps.
I would be very surprised if genetic variations within South Asia is that much greater than genetic variations among caucasians. Concerning diabetes I don’t think recommendations are different for Italians and Swedes, any differences within the two populations is attributed to environmental factors rather than genetic. From an individual perspective I do believe that genetics is the greatest factor when it comes to diabetes.
What do South and East Indians have in common? RICE. Link to diabetes? Perhaps
bing, bong? 🙂
I would be very surprised if genetic variations within South Asia is that much greater than genetic variations among caucasians
1) the word caucasians is confusing, and an artifact of the time when south asians/indians were referred to as ‘hindoos.’ you do have armenian friends right?
2) the rank order in genetic diversity is this:
africans > mid easterners > south/central asians > europeans > east asians > oceanians > new world populations
if you remove african admixture in mid easterners south asians and mid easterners might be a toss up.
Razib what are your thoughts on exercise and S Asians given your study of the genetics?
I’ve always felt that our brethren led fairly sedentary lives in comparison to our peer Americans. But given our diet and genetics it would seem that our weekly hours need to be increased. IE if 8 hours a week of cardio is needed for a caucasian for good health would that number be closer to 12 or 16 hours for a south asian? I wonder.
Is it fair to blame the genetics. I bike 180 miles a week to keep the pot belly away. My brothers do not and they would make handsome desi santa clauses. Our genetics and propensities would be quite similar and yet through choices and lifestyles we look very different.
Is it fair to blame the genetics
no.
Our genetics and propensities would be quite similar and yet through choices and lifestyles we look very different.
right. genes express themselves in an environment. the “norm of reaction.” all groups and families have dispositions. i have a history of type 2 diabetes in my family, so i avoid sugar (my parents long ago switched from white to brown rice). i don’t especially like sweets anyway, so the cost vs. benefit was a no brainer. in contrast i have a friend who has a history of obesity and sweet-toothery in her family, but no history of type 2 diabetes. obesity is bad for other reasons having to do with correlations with other aspects of morbidity, but her cost vs. benefit is clearly somewhat different.
in terms of culture, i remember the frustration a friend of mine (female) had with her mother insisting she not do outdoor sports. part of it was modesty, but part of it was that her mother was worried about too much sun exposure, resulting in darker skin. i recall when i was in bangladesh in 2004 some of the fittest people i saw were peasants in the country. those guys were lean and mean due to the grueling outdoor labor. in contrast, professional city slickers tended to be pale & fat.
I can’t seem to find the website again, but it basically broke down the calorie usage of your typical medieval peasant and it was staggering. It was basically something like 5,000 to 10,000 Calories per day burned.
It’s not just the grueling outdoor labor either. Even basic chores like laundry involve a lot of heavy lifting. You need to carry water from the well just to wash up and even if you were Richie RIch your average day probably involved walking for miles and miles. Oh and if you need to cook you need firewood. I did once have the misfortune of having to chop firewood with hatchet in hand before and dear God is it rough.
Same in Pakistan! In Karachi, most 30+ women tended to look flabby, if not overweight (young women were almost always slender though). Pakistan is hot and humid May – October, and city folk tend to avoid the outdoors, sun, and exercise. At the beach, many young women carried parasols. In contrast, people in the NWFP looked a lot more fit and tan from working outdoors. But I do think that 50 years from now, when South Asians are considerably wealthier, we’re going to be seeing an obesity epidemic in that part of the world, similar to the USA, UK and Australia.
“But I do think that 50 years from now, when South Asians are considerably wealthier, we’re going to be seeing an obesity epidemic in that part of the world, similar to the USA, UK and Australia.”
Definitely, processed foods, sedentary lives…its a lethal combination.
The city planning is also completely FUBAR in India. Getting anywhere involves either taking your life into your own hands by walking or sitting on your duff in a car or rickshaw or (increasingly) transit. Affluent neighborhoods though, are designed along the American suburban sprawl model where you plop a comically oversized but shoddily built house in the middle of a big patch of land in an empty area and call it a day.
But I do think that 50 years from now, when South Asians are considerably wealthier, we’re going to be seeing an obesity epidemic in that part of the world, similar to the USA, UK and Australia.
it’s already happening to wealthier indians and chinese. there are lots of ‘fat camps’ in china for affluent ‘little emperors.’
What a terrible idea, you would think they could see how that failed in North America and decide not to copy that. The traditional urban planning in south asian, the middle east and the mediterranean is so much more natural and conducive to exercise and community. I mean let’s not pretend india is full of women in rural villages carrying water jugs on their heads on their way back from the well every morning, but modernizing doesn’t mean copying what you see abroad. For example, walking around Pakistan, you’ll see lots of traditional houses with flat roofs (typically with clotheslines on top) built around a courtyard, but the newer houses in Pakistan look like they were plucked out of my neighborhood in Long Island, complete with pointed roofs (designed to repel rain) which look comical in the desert climate. I don’t get it. Houses should be designed to suit the natural climate. And when I stayed in Peshawar we always dried our clothes on a clothesline because it was literally faster and more energy efficient than the drying machine. It’s just an example of how giving up the traditional way isn’t always the “better” way. It’s a shame Desi’s are moving away from a more vegetable-based diet to a sugar-loaded diet. Also it’s both funny/sad that literally dirt poor peasant children from villages on the Paki/Afghani border know what McDonalds is, even if they don’t know how to read.
“What a terrible idea, you would think they could see how that failed in North America and decide not to copy that. The traditional urban planning in south asian, the middle east and the mediterranean is so much more natural and conducive to exercise and community. I mean let’s not pretend india is full of women in rural villages carrying water jugs on their heads on their way back from the well every morning, but modernizing doesn’t mean copying what you see abroad. For example, walking around Pakistan, you’ll see lots of traditional houses with flat roofs (typically with clotheslines on top) built around a courtyard, but the newer houses in Pakistan look like they were plucked out of my neighborhood in Long Island, complete with pointed roofs (designed to repel rain) which look comical in the desert climate. I don’t get it. Houses should be designed to suit the natural climate. And when I stayed in Peshawar we always dried our clothes on a clothesline because it was literally faster and more energy efficient than the drying machine. It’s just an example of how giving up the traditional way isn’t always the “better” way. It’s a shame Desi’s are moving away from a more vegetable-based diet to a sugar-loaded diet. Also it’s both funny/sad that literally dirt poor peasant children from villages on the Paki/Afghani border know what McDonalds is, even if they don’t know how to read.”
This is actually excellent and very well put. Thomas Friedman address this notion of Westernisation, as opposed to modernisation, in his book “Lexus and the Olive tree”.
It’s a shame Desi’s are moving away from a more vegetable-based diet to a sugar-loaded diet.
also refined carbs in general. avoiding sugar water (soda/pop) and processed food tends to drop peoples’ weight a fair amount all things held equal.
Refined carbs just never fill you up. I’ve been trying to cut my weight down for the past month and resorted to a high protein and low fat/low carb diet and I’m surprised at how little I actually eat now. It’s like you can just eat 800 Cal worth of rice and be hungry in a couple of hours. Not so with 300 Cal worth of protein and veggies.
I think once I get down to a weight where I can dispense with the severe restrictions I’m just going to switch to things high in dietary fiber as filler rather than the rice and pasta I used to default to.
I’m literally eating a giant spinach-and-potato stuffed samosa dipped in sweet plum chutney while typing this. So good…can’t stop…. :/
the rice and pasta I used to default to.
the glycemic indices of some pastas are not that bad. i wouldn’t put them in the same basket as rice or french bread.
Even so, you can end up eating a lot of it before you realize you’re full. As bachelor chow pasta is a good way to make sure you get a lot of carbs and not a lot of nutrition so eating it by itself without accompanying veggies and such is kind of empty calories.
The Italians generally eat pasta as a single small appetizer course while the main dish will be some kind of meat or eggplant or something. The American mode of making the pasta itself the crux of the meal isn’t as healthy even if it’s better than rice.
Personally I could never cut things like pasta, potatoes or rice out of my diet…so I switched to brown rice, whole wheat pasta and sweet potatoes. A lot more nutritious while still getting those carbs I love 🙂
Unfortunately a lot of people in my extended family find brown rice unfit for consumption, they say it tastes “grainy” (what?) and stick to white rice, which is essentially brown rice stripped of nutritional value.
in other news, zack ajmal now has the biggest data set of south asian genotypes in the whole world 😉 (aside from perhaps 23andMe)
http://www.harappadna.org/2011/03/reich-et-al-and-pan-asian-datasets/
In US, I always thought obesity went hand in hand with poverty. I see lots of poor obese people when i make the dreaded visit to a Walmart. Eating healthy takes considerable time & costs more (For ex: Organic food)
In US, I always thought obesity went hand in hand with poverty. I see lots of poor obese people when i make the dreaded visit to a Walmart.
she was talking about in asia. in india and china obesity still correlates positively with wealth. the inverse correlation is operative in developed nations.
(For ex: Organic food)
organic food is not healthier.
“Eating healthy takes considerable time & costs more (For ex: Organic food)”
Its really about KNOWING what to eat, then taking the care to do so. Chickpeas, black beans, brown rice are all quite inexpensive especially in bulk…you could build yourself into bruce lee living off that. India doesn’t lack for amazing food. But there are stigmas, the one against brown rice that Alina mentioned… try telling your aunts you only want ONE serving of chappati or rice…you’re going to get a slap for sure.
At the end of the day the x factor for desis is exercise, I just don’t see enough desis putting in the hours in the gym and I’m not talking about some half assed spinning. If you’re going to keep the white rice and late night jilabis then cardio MUST increase..and increase by a lot.
“in india and china obesity still correlates positively with wealth. the inverse correlation is operative in developed nations.” Agreed, but in future when they get rid of pure manual labor & use more equipments the poor will have the same risk as the ones in developed countries (In India/China, fast-food culture is picking up pretty fast & rising food prices are not going to help the poor)
Its really about KNOWING what to eat, then taking the care to do so. Chickpeas, black beans, brown rice are all quite inexpensive especially in bulk…you could build yourself into bruce lee living off that. India doesn’t lack for amazing food. But there are stigmas, the one against brown rice that Alina mentioned… try telling your aunts you only want ONE serving of chappati or rice…you’re going to get a slap for sure.
yes. also, in the USA there is the idea of “food deserts” and that you can’t eat healthy if you are poor. i know it’s not politically correct to say, but i think this has gone too far. i think a lot of the issue has to do with the nature of peer culture, and the fact that per caloric unit processed food is the cheapest (and frankly, often the tastiest in terms of sensory quantity). a lot of the reason that people on the coasts are thinner than people in “flyover country” is probably just norms. you eat in groups, and follow group cues.
At the end of the day the x factor for desis is exercise, I just don’t see enough desis putting in the hours in the gym and I’m not talking about some half assed spinning. If you’re going to keep the white rice and late night jilabis then cardio MUST increase..and increase by a lot.
i agree with this. you can substitute “white rice” and “late night jilabis” with “cornbred” and “late night ice cream.” if you carbload, burn it off. if you don’t want to exercise or be active, and want to stay trim, go paleo (though keeping that up indefinitely seems difficult for people).
@Jeevan – You are right about the poverty/obesity correlation in developed countries, but I was talking specifically about South Asia, where people seem to be becoming larger as they get wealthier. I think the differences might due to the following:
“Poor” in America means having to buy more processed food, often artificially flavored, lacking nutritional value, and high in fat content. But “poor” in South Asia often means having very little to eat at all. Fruits and veggies are comparatively expensive in America, whereas in Pakistan I saw that some poor people in the NWFP live almost entirely off of fruits and veggies, which grow abundantly and can be picked out of the ground or off trees. So the diet of poor people varies considerably in different nations. Poor people in America also seem to exercise less on average (“exercise” to an American often means hitting the gym) whereas in South Asia, peasants naturally engage in more manual labor, and walk a lot more, just like the average American used to do.
So true, food plays an important role in our culture…and the traditional desi diet isn’t unhealthy either…plenty of lentils, chickpeas, fruits, etc.
Actually last time I went to India my family surprised me on that front. Now that several of my uncles have come down with diabetes most of my family has gotten pretty health conscious. They don’t get offended when I try to refuse seconds anymore and when they say “taste this” they actually just let me taste it without expecting me to eat an entire plateful.
food plays an important role in our culture
it plays an important role in all cultures. only when societies have had a modicum of affluence does the norm change toward more modesty in consumption. the last fat president we’ve had is warren g. harding (look at the paintings of 19th century presidents, and several of them were quite robust fellows). all the while the nation has been getting fatter.
I agree with the anon comment made about the rice link to diabetes. In the south and in the state of Gujarat people are completely vegetarian (no eggs or fish). Rice, potatoes = starch; legumes = carb; other veggies => sugar. There is very little protein in the diets.