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  #1   ^
Old Sun, Jan-27-13, 09:53
Nancy LC's Avatar
Nancy LC Nancy LC is offline
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Default Why Mom & Dad or Grandma and Grandpa were thin, and you're not.

Possible explanation here:

New Suite of Chemicals May Cause Disease Generations Later: Plastics and Jet Fuel Raise Incidence of 'Epigenetic Transgenerational Inheritance

Epigenetics in a nutshell:

Genes are a blueprint of how the body operates that are passed down from your parents to you. It isn't destiny that if you have a particular gene you'll have a disease, however if you have two copies of a certain gene you'll be much more likely to have that disease (or trait) and sometimes you are guaranteed to have it, it just depends. Genes are potential traits.

There's an environmental component to it too. On top of the genetic structure is another layer that's relatively newly discovered called the "epigenome". This influences the genome and activates or disables genes.

Over a lifetime, identical twins become less and less identical. At the gene level, they're still identical, but at the epigenetic level they begin to diverge at birth.

Nova has a wonderful program on epigetics

Anyway, apparently they are starting to see how epigenetics works and how the epigenome can be passed down to offspring from the parents.

So, the title I posted this as gives us a possible explanation for the obesity epidemic. Things which began becoming commonplace in the 1950's and after start to enter the environment. Mom's begin acquiring epigenetic changes. Those changes might not affect the Mom herself, but her offspring.

Quote:
"Your great-grandmothers exposures during pregnancy may cause disease in you, while you had no exposure," he said. "This is a non-genetic form of inheritance not involving DNA sequence, but environmental impacts on DNA chemical modifications. This is the first set of studies to show the epigenetic transgenerational inheritance of disease such as obesity, which suggests ancestral exposures may be a component of the disease development."
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  #2   ^
Old Sun, Jan-27-13, 10:25
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Liz53 Liz53 is offline
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I saw that PBS special a couple of years ago and it's excellent. They bring up a number of changes that can lead to weight gain. The ones that resonated with me (as someone born at the mid point of baby boom) were those having to do with food restriction and smoking for my mother and maternal grandmother: living through the WWI (food deprivation, my grandmother)l living through the depression (my mother was born in 1929), and further food deprivation during WWII in Canada (which had much long involvement that US). And then there are environmental toxins such as the mosquito spray pumped into the room at bedtime at the cottage, and long term tobacco use by both parents.

I would add that further research is showing that FATHERS can add to the epigenetic changes as well, it's not just mothers. According to the January 17 episode of Fresh Air , children of MEN who smoke are more likely to be overweight and obese.

The plastic water bottles and jet fuel are just one more addition to the long list of things that can alter gene expression. I doubt any one factor accounts for the epidemic of overweight and obesity, and the causes may well be different for each person.
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  #3   ^
Old Mon, Jan-28-13, 09:16
M Levac M Levac is offline
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Quote:
Over a lifetime, identical twins become less and less identical. At the gene level, they're still identical, but at the epigenetic level they begin to diverge at birth.

They can also diverge in utero. Just like one limb can grow longer than another, so can twins develop differently in the womb.

Pottenger's cats is a good example of epigenetics. Although at the time, they didn't understand that yet. From a natural selection point of view, epigenetics makes sense. If one generation is exposed to a certain hostile environment, it makes sense to develop defenses against this environment and develop the ability to transmit those defenses to the offspring so that the offspring is able to defend themselves against this environment from birth, thereby increasing the chance of survival of that offspring, and also the chance of reproduction of that same offspring in the same hostile environment.

However, what we mostly see with epigenetics is the bad sides of it, rarely the good sides. The most obvious reason for this is that we've never been exposed to the current hostile environment until very recently from an evolutionary point of view, thus we don't currently have any defense against it. For such defenses to be developed, it would probably take many more generations yet. The problem with this idea is that we do not die from this environment before we reproduce, therefore we reproduce our defenseless genes, and continue to suffer from the same hostile environment for generations. Instead of natural selection, we now have artificial selection. Man-made selection. This artificial selection comes mostly in the form of medicine.

Remember, natural selection works both by eliminating the unable, and reproducing the able. The unable are those who can't currently cope with the environment or who can't produce offspring, and the able are those who can cope or who can produce offspring who can cope by way of mutation. With medicine and other man-made artificial selection factors, we reproduce a whole lot more of unable than able.

In other words, epigenetics is a mutation which is a survival advantage within natural selection, but not within artificial selection. Logically, this means if we could temporarily disable epigenetics in the parents for the purpose of reproduction, we could produce offspring that could deal with our current hostile environment better than the parents. However, one implication of the above is that we could just ignore the hostile environment, and allow it to worsen to such a point that it would literally become lethal to us without having to disable epigenetics in future offspring.

That's the quick and dirty solution. Is there a less drastic solution? Of course. We revert to a previous non-hostile environment, or a less hostile environment. But where do we start? Easy. With the things we are most often exposed to, and have the most direct and significant effect on our physiology therefore on our epigenetics. Air, water, food. In descending order of collective-to-individual responsibility. There's more environmental factors like noise and light, but those are much less significant factors in my opinion. The problem with this less drastic solution is that it takes time. Generations. Maybe two or three. Just for the effect of those changes to be seen at the physiological and anatomical level. At the genetic and epigenetic level, the effects are almost immediate, if not at most a few years down the line. But when you're already grown up, that's it for that. You won't change how your nose looks. For your kids tho, they might just grow a more beautiful and more functional nose. Deviated septum ring a bell? Still, if we just think of obesity, that could be changed right off the bat in a year or less. If not collectively, at least individually.
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  #4   ^
Old Mon, Jan-28-13, 09:28
M Levac M Levac is offline
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Here's an interesting idea about environmental pollution.

Before industry, how did the environment get cleaned up? Everything that lived produced waste. Sure, most of it was biological, but it was still waste, and without something to clean that up, it would accumulate just like any other waste. So, why not use the same principle to clean up our current dirty environment? My guess is that most of the clean up was done by bacteria and other microbial life. So, use microbes, modify them to eat up or somehow render inert and harmless all man-made pollutants, and we're done here.
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  #5   ^
Old Tue, Jan-29-13, 19:50
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Turtle2003 Turtle2003 is offline
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Very interesting, but not to me. All these theories about why people have gotten so fat in the last 30 years just don't seem to apply to me.

I got fat in my forties. So did my mother. So did my grandmother. So did my great grandmother. Somewhere there was a forty year old fat lady living in a cave in Europe 25,000 years ago and nobody could figure out why she got so fat. She was on a low carb diet after all.
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  #6   ^
Old Tue, Jan-29-13, 21:19
shannone10 shannone10 is offline
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Quote:
Originally Posted by Turtle2003
Very interesting, but not to me. All these theories about why people have gotten so fat in the last 30 years just don't seem to apply to me.

I got fat in my forties. So did my mother. So did my grandmother. So did my great grandmother. Somewhere there was a forty year old fat lady living in a cave in Europe 25,000 years ago and nobody could figure out why she got so fat. She was on a low carb diet after all.


I laughed OUT LOUD at this!!!!

Good luck Girl. Follow you follow me.
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  #7   ^
Old Wed, Jan-30-13, 11:33
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deirdra deirdra is offline
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Quote:
Originally Posted by Turtle2003
I got fat in my forties. So did my mother. So did my grandmother. So did my great grandmother. Somewhere there was a forty year old fat lady living in a cave in Europe 25,000 years ago and nobody could figure out why she got so fat. She was on a low carb diet after all.
25,000 yrs ago I doubt many women lived to be 40 - no wonder they weren't fat.
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  #8   ^
Old Wed, Jan-30-13, 13:46
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Turtle2003 Turtle2003 is offline
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Quote:
Originally Posted by deirdra
25,000 yrs ago I doubt many women lived to be 40 - no wonder they weren't fat.


Not many, perhaps, but there were some who lived that long, and longer. The average life expectancy for people in those days was only about 33, but that low average includes the high mortality for babies and young children.

If you survived those early years your life expectancy was not nearly as bad as 33. A woman living in the late Paleolithic who survived to the age of 15 had a probable 39 more years ahead of her for a total of 54, leaving my ancestor plenty of time to get fat.
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  #9   ^
Old Thu, Feb-07-13, 11:01
jem51 jem51 is offline
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I know exactly why we began getting fat after the 1970's; government intervention aka Food Pyramid.

There is a ton of genetic study and discovering genes damaged by disease will be looked at very closely, I'm sure.

The assumption has been that genes are passed along and that's that....then they see a gene reverse and WTH???
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  #10   ^
Old Thu, Feb-07-13, 15:09
M Levac M Levac is offline
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Quote:
Originally Posted by deirdra
25,000 yrs ago I doubt many women lived to be 40 - no wonder they weren't fat.

But kids and infants grow fat today, so 40 years is ample time to grow fat. Then we have to consider that being fat is not very conducive to survival against predators, so those who did grow fat did not reproduce this trait, because they were too slow to evade predators. This means it's the lean mothers who reproduced, therefore we are their descendants. Obviously, it doesn't explain why we're fat today. Rather, it tells us that we're fat today not because of our genes (the fatness gene got eaten by predators, you see), but because of some other agent which did not exist until recently.

And since today we know that the same thing that causes obesity in humans also causes a slew of other conditions not conducive to survival, we can safely assume that those mothers who did not grow fat, did not develop any of those conditions either, therefore most likely lived to a ripe old age in good health throughout, barring the occasional accident, infection, or failure to evade this particular predator this time around. Furthermore, since survival for humans is also a function of empirical knowledge - don't put your hand in the fire because it burns - it follows that those who lived longer had more experience, therefore used this experience to live longer still. We transmit this knowledge to our descendants. Consequently, we can safely assume that most humans how did survive, lived for a very long time on average, or at least produced offspring that lived a long time.

What this means for obesity is that if obesity was normal for humans at some point, then it must have been suppressed thoroughly simply by virtue of the amount of time early humans lived. The longer, the more chances a bad trait gets suppressed. It didn't get eliminated completely, obviously. And this is where Taubes makes a whole lot of sense when he says "obesity is a disorder of excess fat accumulation". That's because fat accumulation is obviously a strong trait for survival, and obesity is a disorder of this trait.

Through epigenetics, we're now allowing this trait to become bad again, by preventing it from being suppressed, through medicine and food fortification for example.

Last edited by M Levac : Thu, Feb-07-13 at 15:15.
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  #11   ^
Old Thu, Feb-07-13, 15:35
Nancy LC's Avatar
Nancy LC Nancy LC is offline
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Quote:
Originally Posted by deirdra
25,000 yrs ago I doubt many women lived to be 40 - no wonder they weren't fat.

Now they're getting fat early in childhood. Something has changed.
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  #12   ^
Old Thu, Feb-07-13, 16:29
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WereBear WereBear is offline
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I was a skinny, active child. My adolescence happened to correspond to THREE major changes in the food supply:
  • High fructose corn syrup replaced sugar in foods
  • the new, genetically modified wheat replaced the non-GMO kind
  • the removal of animal fats and replacing them with vegetable based trans-fats

Now, I undeniably do better on low carb. But would I have started getting overweight so quickly, at such a young age, if I was still eating the way my grandparents did?

I wonder.
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  #13   ^
Old Thu, Feb-07-13, 21:14
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KarenJ KarenJ is offline
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Quote:
Originally Posted by Turtle2003
Not many, perhaps, but there were some who lived that long, and longer. The average life expectancy for people in those days was only about 33, but that low average includes the high mortality for babies and young children.

If you survived those early years your life expectancy was not nearly as bad as 33. A woman living in the late Paleolithic who survived to the age of 15 had a probable 39 more years ahead of her for a total of 54, leaving my ancestor plenty of time to get fat.


Good point. And true.
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