Brad comments
Your post scratches at some scientific-sounding ideas of the involvement of genetics, but fails to cite any definitive research into inheritable weight-control issues. The mathematics behind maintaining a healthy weight are startlingly simple, and the mythology of “fat genes” and thyroid problems and impossible to shed pounds is merely there to sell books and gym memberships.
The body is a closed system and cannot create additional weight without an over consumption of calories. Joel S is correct — it’s literally impossible to gain weight by eating your “maintenance” number of calories without violating the first law of thermodynamics.
So there are a couple of issues here. One is on whether or not genetics can make a difference. Are there “fat genes?” Does the thyroid matter? The second is whether or not First Law solves the obesity question. I’ll do this in two posts.
On Genetics
I’ll post a couple of links on genetics of obesity and one chart
The chart comes from a paper I am writing on obesity and is based off of data organized by Bruce Scaredote and first used in his paper What Happens When We Randomly Assign Families.
The red dots show the the BMI of mothers plotted against that of their birth children. The blue dots show the BMI of the mothers plotted against that of their adopted children. As you can see the correlation for adopted children is very slight. While the correlation for birth children has a steeper slope.
In both cases we are dealing with heights and weights for all persons reported by the mother. This will tend to introduce measurement error and cause the correlations to be less than the true correlation.
I think its important to note that almost all of the adopted children of morbidly obese mothers, BMI over 40, were normal weight. While the birth children of morbidly obese women tended to be at least overweight if not morbidly obese themselves.
We should also consider the possibility of response anchoring. That is giving a high or low weight for one child will influence the mother’s estimation of the weight for the other child. This will tend to introduce correlation between adopted and birth weights. Which will mean that the two correlations with Mother’s BMI will be closer together than reality. Because the adopted correlation is slight and the birth small, this should lead us to believe that the adopted correlation is even smaller and the birth even larger.
The take home here is that the tendency for whole families to be overweight or normal weight at least seems to work through genetic as opposed to environmental channels.
Other work on obesity and heritability
http://www.ajcn.org/cgi/content/full/87/2/275
http://diabetes.diabetesjournals.org/content/57/11/2905.short
http://www.nature.com/nrendo/journal/v2/n8/full/ncpendmet0220.html
http://www.nature.com/ijo/journal/v32/n7s/full/ijo2008239a.html
3 comments
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Monday ~ April 19th, 2010 at 3:26 pm
Sister Y
The take home here is that the tendency for whole families to be overweight or normal weight at least seems to work through genetic as opposed to environmental channels.
This is an important conclusion: the family-to-family variation in obesity, within a given country/culture, seems to be more about genes than shared environment.
I think the temptation here is to conclude that obesity is genetically “determined” rather than behavioral and environmental. And that’s not what these data say at all. Genetically similar populations living in different countries (e.g., Japanese folks in Japan versus Japanese folks in the U.S.) display drastically different rates of obesity. And the within-country and worldwide rates of obesity and obesity-related diseases have changed substantially over time. A press release from the International Diabetes Federation shows the scale we’re talking about:
“In 1985, the best data available suggested that 30 million people had diabetes worldwide. Fast-forward 15 years and the numbers were revised to just over 150 million. [In 2008], the new figures – launched at the 20th World Diabetes Congress in Montreal, Canada – put the number closer to 300 million, with more than half aged between 20 and 60. IDF predicts that, if the current rate of growth continues unchecked, the total number will exceed 435 million in 2030 – many more people than the current population of North America.” http://www.idf.org/latest-diabetes-figures-paint-grim-global-picture
Tenfold growth in just over twenty years? Genes don’t change that fast. But food supplies and other environmental factors can.
Behavior and environment make people fat – not genes. But genes can make people more susceptible to environments with a McDonald’s on every block. It might be fair to say that a few of us Americans “lucked out” genetically and manage to stay thin despite the incredibly unhealthy food system we have; most people, though, will succumb to obesity when placed in this environment.
Monday ~ April 19th, 2010 at 5:37 pm
Karl Smith
Right – Is there a large group of people who claim that the increase in obesity is not environmentally driven?
I mean I have not seen conclusive evidence that the rise in obesity isn’t due to assortative mating or some other genetic factors but it seems a far far far stretch.
However, I do think that we shouldn’t jump to conclusion about WHAT environmental factor is doing it. It is popular to blame McDonalds but we are just no sure. Lustig goes nuts on sugared beverages. There are some researchers who say the whole thing is autoimmune as is coming hand in-hand with the general increase in autoimmune diseases.
I tend to think most of those explanations are not correct but I couldn’t tell you what is. My money, however, is on a small ubiquitous particle. Otherwise I suspect someone would have stumbled upon a “just don’t eat X and be thin” diet.
Monday ~ September 22nd, 2014 at 2:02 pm
yacon syrup where to buy
Refined sugar, white or brown, literally has zero nutritional value – no
minerals, no vitamins, no fiber, no enzymes, no fats
– nothing of value for the body. Oz’s 28-Day
yacon weight loss experiment were impressive:
A whopping 73% of the women lost an average of 3 pounds each, and 2 inches
off their waists. The flavor is fabulous (we actually like it better than regular PB), and it’s great spread on apples for dessert.