Thursday, February 26, 2009 - Posts
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More evidence today that we've been dieting backward. Instead of asking whether your plan to eat nothing but couscous, kale, and tofu is strict enough, you should be asking whether it's tasty enough.
In the latest study, published in the New England Journal of Medicine, "participants were assigned to and taught about diets that emphasized different contents of carbohydrates, fat, and protein and were given reinforcement for 2 years through group and individual sessions." Result: "The diets were equally successful in promoting clinically meaningful weight loss and the maintenance of weight loss over the course of 2 years."
Why did different diets produce similar results? Not because they're similar on paper, but because they were similarly disobeyed by actual human beings.
Few of the people in the current study strictly adhered to the calorie limits and the composition of their diets, suggesting it is just too difficult to do so ... For example, those assigned to consume 35% of their calories as carbohydrates actually consumed an average of 43%, and groups that were supposed to eat a 20%-fat diet averaged 26%. In the end, many of the participants were eating diets that were more similar than dissimilar.
This study and others "point to behavioral factors rather than macronutrient metabolism as the main influences on weight loss," the authors conclude. "The effect of any particular diet group is minuscule, but the effect of individual behavior is humongous," says lead author Frank Sacks. We had some people losing 50 pounds and some people gaining five pounds."
In short, as Human Nature has argued before, compliance is part of a diet's effectiveness. If you can't stick to a diet, don't just blame yourself. Change the diet. If you can't stand the kale and couscous, stop kidding yourself, and find palatable alternatives.
And when I say palatable, I mean that literally. Diets "tailored to individual patients on the basis of their personal and cultural preferences" may "have the best chance for long-term success," the authors of the new study conclude. According to the Associated Press, Sacks explicitly says the key is to choose a diet that's "tasty." Another researcher, Christopher Gardner of Stanford University, adds, "If one of these approaches is more satiating, where you will not be hungry and have cravings, that is the one that will work for you."
So enough with the quarrels about this or that magic diet for re-engineering your body's chemistry. Think less about your body and more about the part of you whose compliance determines whether the diet has a shot at working: your mind. Is the kale tasty enough? Is the tofu satiating? If not, leave that diet to the saints, and find one that works for the rest of us sinners.
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Not many guys are brave enough to take on Genghis Khan. But then, Genghis never met Hank Greely. Greely, a law professor at Stanford, does a lot of work in genetics and brain science. And he's tired of hearing the tale about Genghis single-handedly (well, "handedly" might not be the precise term) populating the Eastern world. According to the version I quoted yesterday, "8% of males throughout the former lands of the Mongol empire carry the Y chromosome of Genghis Khan."
Not so fast, says Greely:
Here are the facts, as far as we know them. One Y chromosome haplotype is widespread over areas that the Mongols ruled. Genghis ruled the Mongols and had, at least, the opportunity to father many sons, some of whom had similar opportunities. End of facts.
Maybe that's Genghis's Y chromosome, but, as we have no DNA from Genghis (his tomb was hidden) and no certain knowledge of any of his living direct line male descendants, we don't know what his Y chromosome looked like.
Maybe it's the Y chromosome of Genghis's handsome troubadour, or vicious chief of staff, or someone else. We don't know.
And even if it is Genghis's Y chromosome, it's possible none of those now carrying it descended from him. His brothers, paternal uncles, paternal male cousins, etc., all had the same Y chromosome. In fact, if he came from a clan with a lot of males, it probably helped him become the leader. One of the few actual studies showed that 35% of Mongols have this Y chromosome type—is Genghis the cause or the result of that statistic? Who knows?
Do I think there's a good chance that this is Genghis's Y chromosome? Sure, probably as good a chance as anyone and better than most. But how good is that? Who knows. But it's a good story and so it has spread like flu—in part being spread by genetic genealogy companies that are looking for good stories to use that might help convince people to buy their services.
For a more formal version of Greely's critique, see his chapter, "Genetic Genealogy," in Revisiting Race in a Genomic Age, published last year.
Oh, and if you're planning to sue Genghis' estate for your share of the inheritance, don't even think of offering your Y chromosome as evidence. I have a pretty good idea whom the estate will be calling as an expert witness.
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