I say "challenged" because the subject of the article was on a field of science research known as "epigenetics". Now Michelle is the brains of the outfit, but neither one of us are geneticists, and we sure as heck aren't "epi-geneticists". I know enough to know this: it's complicated.
But I like a challenge and it's an area we really haven't put much emphasis on until now. So what follows is more of an editorial breakdown with citations. Here's hoping it sparks a very lively conversation.
Let's start with the premise: Obesity and related conditions are genetic.
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| He's just not that into outliers. |
bell curve. And Mr. Bell Curve tells us that 65% of a population falls around the middle of the curve. About 4% (two on the high end and two at the low) fall into the extreme ends. Are there people who are truly genetically predisposed to be overweight, no matter what? Of course. Just like there are some that will remain lean under almost any dietary / lifestyle conditions. But these are the two-percenters. Might you be one of them? Maybe. But very probably not.
And that's the point of view we are writing from: "You are not the exception; you are the rule."
That said, genetics obviously play a central role in our body composition and function. So, what do we know about the interplay of genetics and environment (or "nature vs nurture")? Quite a bit, actually.
And some of the most interesting data comes from a series of studies on identical twins.
We know that genetics play a significant role in where and how each of us fatten.
Got a gut? Hips? Those under-arm things? Yep, that's genetics. Unfortunately there is nothing we can do to change the way fat accumulates in our bodies.
And here's where we take the first u-turn in our exploration of genetics: Even though your DNA is identical in every cell in your body, how that genetic material functions does differ throughout the body. Think about it: Liver cells do - well - liver stuff. Muscle cells - they have their thing. Fat cells - you get the idea. Even though the genetic material is the same, collections of cells in parts of the body have different attributes "switched on". For example, in skin graft patients, if you take skin from an area of the body that is prone to fattening, that tissue will continue to fatten easily in its new location, even if that area is normally lean. So, it's all the same stuff, but can behave quite differently.
Exploring the Obesity Gene.
In recent years, scientists have isolated a gene that they believe is strongly associated with obesity. It has a charming little name: FTO. Actually, we all have the FTO gene, but a particular variant (or allelle) of the gene has been noted to be associated with increased weight. Now, before you say "That's what I got! That's why I can't lose weight!", let's break down the numbers.
About half of those of European or African descent are estimated to have the gene variant, while about 14% of those of Asian descent have it. Among those that do, studies indicate an average of 2-7 pound difference (less if you have one instance of the variant, more if you have two instances). So we're not talking about an insurmountable amount of weight difference here. So, the average American has a 50-50 chance of having a gene combination that may cause them to weigh five-ish pounds more than a similar person who doesn't.
It's sounding like a little less of a big deal isn't it?
Additionally, a series of the studies on the FTO gene indicated that it was associated with increased appetite / energy intake, but did not result in a reduced ability to expend energy. In short, the gene doesn't make it physically more difficult for a person to lose weight, but seems to indicate a person more prone to gaining it.
Genetics alone aren't a prescription for obesity, lifestyle is.
As I mentioned, some of the most revealing studies about obesity and genetics involve identical twins. One study examined twin pairs where one was obese and the other wasn't. The two were, of course, genetically identical, as well as having the same upbringing, access to activity, and, presumptively, attitudes about food. Yet one was overweight and the other wasn't. In itself, the existence of these pairs refutes the theory that genetics are the central cause of fattening.
The study conducted detailed blood analyses of the pairs. The results are very much worth noting.
Each pair's blood work was in a somewhat different range. But the difference between the obese twin and the leaner one was a pattern that repeated again and again. The obese twin always had higher insulin resistance, higher fasting blood glucose, higher triglycerides, and lower HDL cholesterol. There were also increased levels of Omega-3 fatty acids in the lipid profiles of the obese twins.
But my father was fat, and my grandfather too...
We derive our attitudes, behaviors, mannerisms, and habits through the imprint of those around us in our formative years. Many of the conditions that have traditionally been considered to "run in families" turn out to be primarily lifestyle-related. If you do the same thing over and over, expecting a different result, Einstein says that's insane. Heredity may be a factor, but odds are, inhereted behaviors are the more likely culprit.
Genetic disorders that lead to obesity
Energy regulation comes down to hormones. The two most common hormonal conditions that likely have a strong genetic component are hypothyroidism (Hashimoto's Disease) and Type I Diabetes. Both are autoimmune disorders that prevent the body from producing sufficient hormones to properly regulate energy and frequently lead to obesity. Both are noted to "run in families" but genetic association does not guarantee the condition (in twins where one of them is Type I, the other is only 30-50% likely to have it as well), nor does the lack of a family history guarantee immunity. So it is likely a combination of factors. A genetic susceptibility, triggered by environmental factors, possibly en utero, come together to trigger the full-blown condition.
You can't change your genes anyway... or can you?
Which brings us back to the beginning and epigenetics. Epigenetics is an evolving science - even the definition of the word itself is somewhat in dispute. But, in general, it has to do with things that influence and impact our genetic functions. Remember earlier that I mentioned how different cells have different attributes "switched" on or off, based on their function. That switching is at the heart of epigenetics.
A recent study discovered a form of micro-RNA that has the ability to switch off the FTO gene variant in our fat cells through exercise. What exactly causes this switching activity is not clear, but unrelated studies do show that fit people show some "immunity" to the effects of overfeeding. It opens up some interesting possibilities. Maybe "nature" and "nurture" aren't mutually exclusive after all.
IF you are one of those that has the FTO variant, and IF the micro-RNA switching is, as the study appears to indicate, directly influenced by exercise and weight loss, then, as those switched-off cells reproduce, you develop an ever increasing number of FTO-inactive cells throughout your body, which could, over time, result in a person becoming like those in the non-FTO population. It seems like a lot of conditions just to capture a five-pound advantage, though, doesn't it?
Boiling it all down
carriers of the FTO "fat gene" variant, may predispose people to overeating to a degree - but not a huge degree. Twins identical in all aspects but weight showed the key differences are in factors primarily affected by nutrition, not bodily function. And those nutritional factors are reflective of people overwhelmed by high-glycemic index foods in their diet (insulin resistance, high fasting glucose, and high triglycerides/low HDL cholesterol).
We're all born with the bodies we've got and will reside in the rest of our lives. Each one is unique in its natural strengths and weaknesses. But, for most of us, we can minimize or overcome weaknesses and maximize strengths through a planful application of nutrition and meaningful exercise.
What is true is that, whatever path a person is on, fattening or getting leaner, there is a cascade effect of either negative or positive outcomes, which continue and multiply their impact to the body. That can make it feel like the kind of uphill battle that must mean your body is working against you. To break the cycle, the best bet is to break it in multiple places at the same time.
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