[Wild Fragaria]

It's a very 'surface' research, but it looks interesting

Published online: 16 March 2007; | doi:10.1038/news070312-9

Researchers have used a new technique to hunt for rare genetic quirks that explain why some people are extremely fat or very thin.

The researchers, led by Len Pennacchio of the Lawrence Berkeley National Laboratory in California, studied 757 Canadians from Ottawa. Half of the participants were chosen because they were fatter than 95% of the general population for their height: on average they weighed 125 kilograms. The other half was thinner than 90% of the population, with a mean weight of 57 kilograms.

The team examined 58 genes known to be related to obesity, appetite, or the conversion of food into energy, in every participant. They looked for tiny differences between people in the series of chemical building blocks that make up each gene. This technique, called medical sequencing or resequencing, aims to discover rare genetic variations that may subtly influence particular traits — including body size.

Most previous genetic trawls have focused on using the HapMap — a catalogue of common genetic variants shared by most people with a certain disease. Resequencing is different, as it looks for genetic quirks that are unique to just a few individuals. Resequencing studies have been used to find variations that may cause cancer and differences in cholesterol, whereas HapMap studies have been used to hunt for more common variations that contribute to a range of conditions, including diabetes (see 'Broad sweep of genome zeroes in on diabetes').

Pennacchio's team found 1,074 genetic variants in the sequenced genes, they report in the American Journal of Human Genetics3. Most of these variants were rare, meaning they were found in less than 1% of the study participants. The fat participants had significantly more variation in the genes known to be linked to severe obesity. But when the team looked for the same rare variants in family members of the affected participants, they couldn't link the genetic difference directly to body size. So each variant on its own isn't enough on its own to make a person fat or thin.

"Obesity is such a complex condition — it's not a black-and-white thing — so it doesn't mean these genes might not contribute to weight differences, it just says they're not clearly causative on their own," Pennacchio says.

Scientists are unsure how much rare and common genetic variants contribute to disease, especially in complex disorders such as obesity, which are caused by multiple environmental and inherited factors. And it is proving hard to pin down — at least for now. Resequencing studies are more difficult and expensive than HapMap studies, so fewer scientists have done them.

"We could show that there are rare variants that have a significant difference between obese and lean subjects, but even with the amount of sequencing we've done, we can only scratch the surface," Pennacchio says.

As the cost of resequencing studies drops, Pennacchio predicts that the problem will be cracked. "This is going to be a big growth area for the field."

[Ulala]

Interesting. I'd always considered a lot of it to have to do with how the person was raised as this affects what they eat, how much they eat, activity levels in turn affecting metabolism...

[Mobius]

Pennacchio

But we don't need a scientific research to demonstrate this.

[aldo_14]

My only worry about this sort of research would be fat people expecting some form of genetic cure for their condition rather than simply taking care of themselves; I'm curious, though, how selection would affect the retention of a 'fat' gene - on the one hand, fat is bad for, well, reproducing; but on the other hand perhaps the drive to eat, or more efficient fat storage (or lower use rates) would be handy in early evolution when food was scarce.

[IceFire]

Aldo...I don't think its necessarily that fat people were the selector but rather people with larger body mass having an advantage in strength related activities.  You've got the people with big bones and big muscles, the people with medium bone and muscle and people with thin bones and muscles.  There's names for those body types that I forget...anyways when I read about these I found it quite revealing.  The medium folks are actually the typical athlete / jock type that we associate with in modern times.  The ones with heavy mass are now typically, but not always, the people we associate with as being "fat and inactive" and then we also have the really thin ones who are associated with as thin but really these people are runners.

But in a scenario where there's a group of people out fending for themselves and food...then the people who gain body mass quickly are generally also those who can engage in activities where allot of strength is required because they have muscle mass (from activity) to offset the weight and the fat is actually just really good storage for when they need to use their strength.  The folks in the middle are useful in either capacity and the lighter weight ones are great at running down prey or doing activities that require a high degree of flexibility or dexterity.

This is partially on reading and partially just my own musing but I think it makes sense.  Basically in any given group of humans you need to have a wide variety of personality/trait types as well as physical types in order to offer the best chances for the whole group to survive.  In modern times there is too much food...but body types are still present.  People who are heavier will still be stronger if they work out than I ever will be.  I on the other hand, having a thinner type, am quite a bit more agile.

Just my musings.

[aldo_14]

Aldo...I don't think its necessarily that fat people were the selector but rather people with larger body mass having an advantage in strength related activities.  You've got the people with big bones and big muscles, the people with medium bone and muscle and people with thin bones and muscles.  There's names for those body types that I forget...anyways when I read about these I found it quite revealing.  The medium folks are actually the typical athlete / jock type that we associate with in modern times.  The ones with heavy mass are now typically, but not always, the people we associate with as being "fat and inactive" and then we also have the really thin ones who are associated with as thin but really these people are runners.

But in a scenario where there's a group of people out fending for themselves and food...then the people who gain body mass quickly are generally also those who can engage in activities where allot of strength is required because they have muscle mass (from activity) to offset the weight and the fat is actually just really good storage for when they need to use their strength.  The folks in the middle are useful in either capacity and the lighter weight ones are great at running down prey or doing activities that require a high degree of flexibility or dexterity.

This is partially on reading and partially just my own musing but I think it makes sense.  Basically in any given group of humans you need to have a wide variety of personality/trait types as well as physical types in order to offer the best chances for the whole group to survive.  In modern times there is too much food...but body types are still present.  People who are heavier will still be stronger if they work out than I ever will be.  I on the other hand, having a thinner type, am quite a bit more agile.

Just my musings.

Well, early human evolution would necessitate strong bodies simply through a ****load of excercise, but IIRC a layer of fat does have an evolutionary advantage in terms of things like heat retention, famine, etc.   I'm not necessarily saying that fat people (or, rather, those predisposed to be fat in modern conditions) would be selected, but that such a gene would be retained in the genepool for survival reasons, and I'm curious what sort of 'precedence' it would take over the alternatives (clearly it's not universal if we have variance in metabolism or fat retention).  Presuming it isn't a 'linked' gene (i.e. to some other characteristic that would be selected; this has been hypothesised, for example, as a possible justification for a homosexuality gene being retained in the population).

Albeit I would note that the predominant form of food intake for early man was from the females foraging for food and, whilst hunting was a nice competitive behaviour for males, that's one half of the species which perhaps had less of a strength need (albeit was still bloody strong by modern standards).

[Agent_Koopa]

There's names for those body types that I forget...anyways when I read about these I found it quite revealing.

Ectomorph, mesomorph, endomorph, in order from skinniest to largest.

[MP-Ryan]

There's names for those body types that I forget...anyways when I read about these I found it quite revealing.

Ectomorph, mesomorph, endomorph, in order from skinniest to largest.

All of which are total scientific nonsense.

[MP-Ryan]

Ah, the genetics of obesity and the evolution of Homo sapiens...

Let's clear something up.  In evolutionary terms, any animal that can eat as much as possible and store it during times of resource plenty is going to have greater survival rates than one that can't - because when a time of starvation hits, that animal is going to survive.  This is true even of humans.

Of course, the unfortunate part is that modern human behaviour has evolved faster than modern humans genetics.  We have all kinds of genetic remnants that hinder us in the kinds of lives we live in a modern world.  Fat storage is just one of those.

That said, and while I know a great deal about how genetics influences our lives, obesity is not a strictly genetic issue.  It is a social issue.  Our genes may predispose us to a certain body type, but our choices in social life are what determine what actually occurs.  Many people have the misconception that because a genetic link exists there is nothing that can be done about a condition.  All a genetic link is is a possible factor related to the condition.  It's not a sentence, it's certainly not a destiny.  People need to remember this.

[aldo_14]

Ah, the genetics of obesity and the evolution of Homo sapiens...

Let's clear something up.  In evolutionary terms, any animal that can eat as much as possible and store it during times of resource plenty is going to have greater survival rates than one that can't - because when a time of starvation hits, that animal is going to survive.  This is true even of humans.

Ah, but what about the role of sexual selection?

[redsniper]

Back in the day, fat was sexy.

[aldo_14]

Back in the day, fat was sexy.

Quite possibly

[MP-Ryan]

Ah, the genetics of obesity and the evolution of Homo sapiens...

Let's clear something up.  In evolutionary terms, any animal that can eat as much as possible and store it during times of resource plenty is going to have greater survival rates than one that can't - because when a time of starvation hits, that animal is going to survive.  This is true even of humans.

Ah, but what about the role of sexual selection?

When the Americas were being settled by Europeans, the men chose hefty wives quite intentionally.

This fascination with 'thinness' is only a very recent phenomenon, and it's only become relevant with the kinds of foods we eat and the nutritive value of them.

[aldo_14]

Ah, the genetics of obesity and the evolution of Homo sapiens...

Let's clear something up.  In evolutionary terms, any animal that can eat as much as possible and store it during times of resource plenty is going to have greater survival rates than one that can't - because when a time of starvation hits, that animal is going to survive.  This is true even of humans.

Ah, but what about the role of sexual selection?

When the Americas were being settled by Europeans, the men chose hefty wives quite intentionally.

This fascination with 'thinness' is only a very recent phenomenon, and it's only become relevant with the kinds of foods we eat and the nutritive value of them.

Well, I'm curious as to how inherent/inherited it is (versus environmental).

[MP-Ryan]

Well, I'm curious as to how inherent/inherited it is (versus environmental).

Which?  Obesity, or the role of sexual selection IN obesity?

As I said in my longer post earlier, with humans you have to keep in mind cognitive and behavioural aspects that have evolved beyond our mere genetic makeup.  Some conditions are strictly genetic, but obesity isn't one of them (nor are other eating disorders).

Genetics can predispose you toward many conditions, but ultimately the majority of them have a large beahvioural component as well.

[aldo_14]

Well, I'm curious as to how inherent/inherited it is (versus environmental).

Which?  Obesity, or the role of sexual selection IN obesity?

As I said in my longer post earlier, with humans you have to keep in mind cognitive and behavioural aspects that have evolved beyond our mere genetic makeup.  Some conditions are strictly genetic, but obesity isn't one of them (nor are other eating disorders).

Genetics can predispose you toward many conditions, but ultimately the majority of them have a large beahvioural component as well.

Not obesity per se, but the more general thread of how much a role sexual selection plays in determining body shape (as much as it can be controlled through genes), and in determining sexual preference.  For example, there are obvious sexual selection reasons for favouring, ummm, larger bodied (but not obsese or of a 'liability' physical state) in early evolutionary terms, but I'm curious as to the weight that has on the overall mechanisms for sexual preference and how it interplays with the societal role.  In essence, whether there is or was a general trend towards sexually selecting larger women (or men, I guess, although I think weight is more important in child nurturing ability for woman - offhand) in human evolution (I would expect so, and IIRC it's still evidenced in African societies for example), and how much of that trend is preserved in the genetics of attraction, and indeed how much those genetics may have changed over the years, plus finally how important overall genes are in determining what attracts us vis-a-vis the general miasma of society.

[IceFire]

I think the studies done on attractiveness of women showed that although the sizes varied depending on culture (from sub Sahara Africa to Europe to North America) but that the overall proportions remained similar.  I suspect there is a point in that where you can't have that "perfect shape" anymore if you're carrying too many pounds.

I'm not as aware of studies done with women on how they see men and physical attractiveness but I imagine there are certain ratios and that if you're too overweight then the ratios are all off.

[Agent_Koopa]

There's names for those body types that I forget...anyways when I read about these I found it quite revealing.

Ectomorph, mesomorph, endomorph, in order from skinniest to largest.

All of which are total scientific nonsense.

The personality types associated with them are total tripe, but the three types themselves are (actually rather broad) bona fide categories to classify people with.

[IceFire]

I'm not an expert on the subject...but its my personal experience that different body types and different personality types seem to be correlated to some degree.

[MP-Ryan]

I'm not an expert on the subject...but its my personal experience that different body types and different personality types seem to be correlated to some degree.

There's no scientific basis for that though.  We can all think of anecdotal examples, but personal stories do not make for empirically testable hypotheses =)

This is why I said they were total scientific nonsense - the historical association of body type to personality.