| Fat Genes And Why We Shouldn't "Fix" Them |
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I'll start off with a definition: A fat gene is (at least for the purposes of this article) a gene which makes the carrier more likely to become obese. As with other genes, just carrying it doesn't guarantee any particular outcome, but it does influence it. Some people have been known to say that they're a myth. Why I think they exist: The evolutionary argument (also called the "Thrifty Gene Hypothesis"): (If you're not convinced about evolution, go here as they have a much better explained argument than I can put forward concisely): consider ancient times when a sizable fraction of each human generation died before reproducing. In such an environment, natural selection still holds sway over human genetic change. Consider more specifically a famine. As the famine begins there will be a wide variety of people. If the famine extends for long enough, however, some people will start to die. Obviously the very old, the very young, and the otherwise infirm will die first, as in any life-threatening circumstance. If it goes on just a little while longer, then some folks in the prime of life will die. The question that matters is: which will die first? The obvious answer is that the first to die will be those with the least fat stores in their body. The two possibilities for having low fat stores in this era are that (a) an individual wasn't very good at getting food, and thus had never stored up much food, or (b) the person had burned off their fat stores early in the famine. Option (a) merely represents someone who doesn't compete well in the natural world. Option (b), however, is someone who has "thin" genes. Thin genes in the modern day are, if anything, a slight benefit. They make the individual look "better" (meaning our modern sensitibility is that thin is beautiful). In ancient times (meaning any time before modern farming came about), however, being prone to thinness was a distinct disadvantage. Thin genes meant that when there was ample food, your body would metabolize most of it and not store much away. Then when hard times came about, you were more likely to starve. Since the long term trend for almost all human populations has been one of intermittent famine, the tendency would be for the "fat genes" to proliferate within a population. My guess is that these genes would probably operate by causing more efficient use of calories in general, and by turning on a "starvation mode" in which metabolism is slowed greatly. The observational argument: There is at least anecdotal evidence of individuals with definite fat genes. There is a story (which I am unable to find a link to currently, please inform me at srehnadmin@gmail.com if you know of it) of a woman who weighed over 300 pounds who was unable to lose weight on a 500 calorie/day diet (which is less than 1/3 of a low-normal dietary range). Such a low dietary intake is dangerous in itself as it's almost impossible to get enough non-caloric nutrients with such a light diet. Conversely, most of us know of at least one person who eats incessantly, is very thin, and can never gain a pound. This is apparently an example of someone with thin genes. Effects of fat genes today In an environment of only moderate or intermittent food supply someone with fat genes would not become obese (or would not remain that way for long). In a modern economy with plentiful cheap food, however, obesity proliferates. Assuming some such starvation mode exists, it would presumably be triggered quite well by the modern style of fad diet. A diet in which one eats enough less food for a few weeks to lose a couple of pounds and then quits is exactly what would cause a net weight increase assuming a fat gene with a low calorie intake trigger exists. The "Fix" The "Fix" to fat genes would be to genetically engineer those who carry the genes so that they no longer carry them. The easiest way to do this would be to measure which genetic traits correlate most strongly with obesity, but do not correlate with other cofactors (such as income). Then, either an adult's genetics would be modified by a virus or similar protein machinery to replace the "fat" genes with their thin counterparts, or a zygote (fertilized egg cell) would be modified in this way. The net result would be to replace the fat genes in the population with thin genes (at least among those who could afford the therapy). What's Wrong with the "Fix" The solution above would be okay if one assumes that the current condition of cheap and plentiful food will continue forever. That, however, is improbable bordering on impossible. The most obvious situation showing the flaw in this thinking is the "fall from grace"; ie if our modern high-tech economy falls apart some day. If this were to happen, then our previous pattern of intermittent famines would almost surely take over. The problem is that if we've gotten rid of the fat genes completely, it's possible for us to all starve. Similarly, in the future we might get the technology together to colonize a new planet. In such an undertaking, it's quite possible that some lean years might ensue. It would be a shame if such a grand undertaking were to fail because of a foolish use of genetic engineering technology to undermine our species ability to survive hard times. A Temporary Solution is Best The obvious solution to the problem of obesity, therefore, is to come up with something that would allow people with fat genes to avoid obesity, but which only acts temporarily. An example would be a drug which increases an individual's metabolism to a desired point. There already exist such drugs; unfortunately the side effects are more likely to kill the patient than the original obesity was. The drugs I refer to are stimulants (Cocaine, amphetamines, ephedra, caffeine, etc.). The only one of that list currently legal in the US is caffeine, which once people gain a tolerance to it has almost no weight loss effect. The ideal solution would be one which mimics the hormonal and enzyme state of a person with "thin genes" without changing the genetic makeup of the idividual. Simply stop taking the drug, and eventually your metabolism would return to normal. I feel that such a drug is inevitable as our understanding of the recently decoded human genome becomes more complete. As we come to understand the functions of the various genes in the human body, we'll be able to identify those which cause the body to store excess fat. From that it's only a small leap to change their effect. In the meantime, the best solutoin I know of (since I seem to have a mild case of fat genes myself) is to find a reasonably low calorie diet you can stick to for years running. Since the problem of fat genes is only exacterbated by yo-yo dieting, very long stable diet is essential. Regular exercise can hardly go wrong either. |
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