Posted on 09/15/2010 3:15:53 PM PDT by neverdem
When it comes to our expanding waistlines, we usually blame either diet or genes. But a new study fingers a third culprit: chemicals that attach to DNA and change its function. A survey of millions of these modifications has uncovered a handful associated with body mass index, a measure of height and weight. Although the findings don't prove that the modifications cause obesity, they may one day help doctors better predict who should be counting their calories.
The chemicals in question are known as methyl groups, and they act a bit like volume knobs on our DNA. They can turn the activity of a gene up or down, and even on and off. Some of these modifications—known as epigenetic changes—are inherited; some are acquired throughout life. Only in the past 5 years have researchers begun to comprehensively map which DNA sequences in a person are methylated.
At Johns Hopkins University School of Medicine in Baltimore, Maryland, M. Daniele Fallin, Andrew Feinberg, and their colleagues decided to build large-scale maps of such "epigenomes." Their goal was to see whether epigenomes varied from person to person, like fingerprints do, and whether the pattern of chemical modifications was stable in an individual throughout his or her life. Using innovative technology developed in Feinberg's lab, the researchers took DNA samples from 74 Icelanders and in each examined 4.5 million places along the human genome where methylation can occur. The Icelandic people are part of a long-term study in which their health status and white blood cells have been collected regularly since 1967. "The scale of this [epigenetics] study is unprecedented," says Kun Zhang, a genome technology researcher at the University of California, San Diego.
The team found 227 DNA regions with different methylation patterns from person to person. Of those, 119 remained the same over the decade within each person, providing an epigenetic fingerprint for each individual, the researchers report today in Science Translational Medicine. Many people expect methylation patterns to be constantly changing. "To find so many sites of methylation that were consistent over time was kind of surprising," Feinberg says.
Next, the team looked to see whether any of the methylated DNA correlated with body mass index. Thirteen did. With some genes, the higher the body mass index, the greater the methylation; with other DNA sequences, the reverse was true. Four of the 13 methylation patterns remained the same between 1991 and 2002 in the individuals examined. Among the 13 methylation sites, about half harbored genes that have previously been linked to or were suspected of contributing to obesity or diabetes. Other genes highlighted by the methylation study, such as one involved with foraging behavior in rodents, were a surprise. Still, says Feinberg, "it's too soon to say if [the methylation fingerprint] is predictive of disease."
Geneticist Carmen Sapienza of Temple University School of Medicine in Philadelphia, Pennsylvania, is optimistic, however. To date, genes identified as associated with obesity and other common diseases have not been very useful for assessing who is most at risk or for developing new treatments because each gene has such a small influence on disease risk. But adding in these epigenetic fingerprints might help make genetic information more predictive, he points out. If validated, notes Zhang, these patterns could "allow at-risk individuals to adjust diet or lifestyle to control their weight."
Science News wrote that the title was, "Personalized epigenomic signatures that are stable over time and covary with Body Mass Index," but the DOI it gave would not work. Science Translational Medicine's apparent link to the citation linked an abstract about cancer instead.
Or you could just notice that your pants don't fit and stop stuffing your face.
Where calories in > calories burned off, fat results.
Building and retaining muscle mass has the happy effect of making even sedentary pursuits burn off more calories, as it elevates the metabolism. It isn't necessary to be a ropy-muscled grotesque caricature, either- just firm up what you've got and maintain it.
My girlfriend has 2 volume knobs.
Just look at photos from the not-so-distant past. Most Americans a few decades ago were not obese; in fact most were downright thin by today’s standards, but people did not ride everywhere in cars in those days, nor did they guzzle sodas whenever they were thirsty.
The difference between our family photos and others is that the photographers always stood way way way back to get everybody in both vertically and horizontally.
The result was a tremendous savings in the cost of photos ~ which is why we have some of the big guys.
Never fear there were always large people around ~ even going back into the 13 and 1400s ~ the Iroquois warrior elite was typically 7 ft tall!
I think mine goes to 11.
Some people from Polynesian islands are genetically programmed to be huge, which is partly why there are so many Samoans in the NFL. Pima and Papago Indians tend to be obese, because their ancestors were adapted to a harsh desert environment where starvation was a constant threat. However, the prevalence of obesity in today’s American population is unprecedented. I look at photos of Americans from a few generations ago and see people who mostly look downright skinny by modern standards. I remember as a child that most of my colleagues were not fat. We went everywhere on foot or on bicycles. We were not ferried to “youth activities” in minivans equipped with cupholders, the better to carry high-fructose soft drinks.
Not true. People have been dealing with unwanted pounds since Greek and Roman times at least. I have family pictures from the late 19th and early 20th centuries, and they all resembled one another - short and definitely on the chunky side. All these people did hard physical labor every day, but they were still hefty. No sodas and not wealthy enough to own a car.
Genes have everything to do with it, and for those people who continue to be hateful about this, I only hope they some day experience what it is to struggle with their weight.
People like the Pimas and Papagos were endowed with an unusual capability to conserve energy and fat. All human races to some degree have this ability to store fat against famine, because for most of our evolutionary history, life was very hard, and survival "iffy." We needed the ability to survive famine .When the Industrial Revolution and fossil fuels made it easy to grow a surplus of food year after year, people became vulnerable to obesity.
I once weighed nearly 300 lbs and am now in the high 180s (”normal” weight for a man my height) so I know both sides of the coin.
I do strengh training or cardio nearly every day and my friends remark at how little I eat. I determined my caloric needs to be no more than 1200-1500 calories depending on the foods. I never feel full and often times eat less than women do. Sometimes, I won't feel hungry all day if I'm stuck behind a desk.
If I eat any more than that, I gain fat instantly. My friends normally eat double that, don't work out regularly and have always been thinner. When I ate like my friends, I became 300 lbs.
I like to hike, and have been surprised to see people who are outright obese climbing mountains. I have also seen really old people making it to the top. However, I am reminded of the saying that there are "old pilots, and bold pilots, but no old bold pilots." I have yet to see any old obese hikers!
When it comes to our expanding waistlines, we usually blame either diet or genes.What the hell is that supposed to mean, ya bunch of toothpicks?!? ;')
Well, that explains it. I should never have gotten all that MEK in my mouth from siphoning it into the photoresist stripping tank in the late 70’s - early 80’s. Sigh...
I read long ago, that Sarah Bernhardt (considered quite a beauty in her day) weighted in at 200 lbs.
Marilyn Monroe would be considered too “chubby” by today’s standards.
But, many of us are way too fat these days. And, it is our processed foods, not the amount of good fats in our diets.
Then you should see the pictures of my hikes on Facebook :>)
I am an old (56) overweight (245) hiker! Went to the 8600 ft level on Mt Rainier in July.
What is the elevation you started out at on Mt. Rainier? I find that elevation gain is the main determinant of how strenous a hike is. Also, 8600' is higher than anything in this part of the country, and the air is thinner, making any exercise harder.
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