Obesity and Calico Cats

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Obesity on the decline?

Is this the best news of the week? The news that obesity in little kids has gone down dramatically here in the US? Researchers at the government’s National Center for Health Statistics claim, in a JAMA paper, that obesity from age 2 to 5 has fallen from 13.9 percent in 2003-04 to 8.4 percent in 2011-12.

Greet these data with little glad cries, and hope madly that these kids, and those who come after, can continue to maintain healthful weight as they navigate through the crises of life. But absorb also the fact that it’s at best a dent in the obesity statistics. As the paper points out, obesity hasn’t declined in other age groups.

Also, read analyses from Zachary Goldfarb at Wonkblog, which I am pleased to report continues its focus on data even though Ezra Klein and (some of) Co. have departed for their ambitious explanatory news startup.

In another post, Goldfarb points out the disheartening news that the decline among young kids does not show up in all ethnic groups: black and Hispanic little kids are still often fat. It’s the white kids who are less so. “We’re celebrating the fact that for all kids ages 2 to 5 childhood obesity has declined from 13.9 percent to 8.4 percent over 10 years. Yet, 11.3 percent of black children ages 2 to 5 and 16.7 percent of Hispanic children that age are obese. Just 3.5 percent of white children ages 2 to 5 are obese.”

At Covering Health, the blog from the Association of Health Care Journalists, Joe Rojas-Burke explores some potential reasons for this divide, which range from income disparities to lack of exercise (due in part to the lure of video games.)

The JAMA report attributed the decline largely to government programs. These include food stamps (which have of course just been cut) and the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC), plus new nutrition and physical activity standards for early child care programs,  Other factors include a reduction in smoking during pregnancy and in TV  fast-food ads targeting children.

And, of course, Michelle Obama’s “Let’s Move” program, along with similar efforts by professional groups. I don’t know how deliberate the timing was, but the Obama administration has just announced restrictions on the marketing of junk foods and sugary drinks on school campuses.

Credit: fbotero

Credit: fbotero

Is breast best for obesity?

Also on the list of factors that may have contributed to the decline in obesity among kids 2 to 5 is increased support for breastfeeding mothers. Reducing the risk of obesity is just one of the benefits that has been attributed to breastfeeding.

Surfacing this week, however, is another paper that casts doubt on the now-conventional wisdom that Breast Is Best. It was published in the journal Social Science & Medicine, and uses a clever technique for getting around the confounding effects of race and income that make studying the effects of breastfeeding messy.

In addition to comparing subjects from general populations who had been breastfed versus those who had not, the researchers compared subjects in the same family, one of whom had been breastfed and the other not.

In her blog comments on the paper, Amy Tuteur, the Skeptical OB, concluded, “Simply put, looking within families takes ethnic, cultural and socio-economic factors out of the picture. When you do that, you find no difference between breastfed and bottlefed children.” The research compared subjects on a number of outcomes, including obesity.

The paper is very long, and Tuteur’s analysis is useful because it picks out a few salient points and helpful charts. But keep in mind that Tuteur’s skepticism has long extended to strong claims for the benefits of breastfeeding. She tells us at the outset that she believes “although the benefits of breastfeeding are real, they are small and restricted to relatively unimportant risks like colds or episodes of diarrheal illness during the first year of life. To hear lactivists tell it, however, breast milk has super powers and women who do not breastfeed are bad mothers.”

You will not be surprised to learn that this Feb. 26 post has already attracted hundreds of comments. I haven’t read them, but will wager that many are not complimentary. Lactivists.

What causes obesity?

At the PLOS blog Obesity Panaea, Travis Saunders attributes the growth of obesity in children to four factors he says he’s pretty sure about: Sugar-sweetened beverages, sedentary behavior (especially screentime), lack of sleep, and adult obesity. He says the data on other possibilities are either weak or in conflict. These possibilities range from the the obvious (like diet), to the less so (like gut microbes and a lack of breastfeeding.)

Since he’s convinced it’s a factor in obesity, I wish he’d said more about lack of sleep, which is a theory I don’t know much about and haven’t the time to delve deeply into at the moment. OK, sleeping less means more time to eat, perhaps especially if lack of sleep is due sedentary pursuits like late-night TV. But there must be more to it than that, right?

Nature and nurture in obesity

At about the same time as the CDC paper, another JAMA journal, Pediatrics, also weighed in on childhood obesity. It published studies of genetic variation in satiety responses, aka appetite, in non-identical twin youngsters. An accompanying editorial, apparently written from the Department of Duh, concluded that these genes vary among individuals.

The papers prompted fulmination from David Katz, editor of the journal Childhood Obesity, in a post at HuffPo. He argues that gene studies are pretty much irrelevant to solving the problem of childhood obesity, pointing out that people had pretty near the same genes a few decades ago, when childhood obesity was much rarer.

It’s a long post with a convoluted and repetitive analogy between appetite genes and genes for gills–don’t ask–but there’s no arguing with his conclusion: “Can we really justify the lunacy of a culture that studies genes looking for variation in satiety responses, while engineering foods to undermine satiety responses?”

Hot news and not news about coat color genetics in calico cats

The Christian Science Monitor thinks that inactivation of one of the X chromosomes, which happens in all mammals but no other animals, and which Mary Lyon discovered in 1961, is new news.

Unfortunately, the New York Times picked up the Monitor story and treated it as new news, too. Now that this misleading factoid has appeared in the Newspaper of Record, it will no doubt be promulgated as a 2014 discovery forever in term papers, and cribbings of term papers, not to mention encyclopedia articles and probably several books.

I suspect this happened because it involves cats and pictures of cats, irresistible eye candy that seem to result in brain freeze and abandonment of professional responsibilities.

X inactivation is the reason for fur color in tortoiseshell and calico cats. The X chromosome is turned off at random in mammalian females. Some cells reflect Dad’s X and some Mom’s. Fur color genes are on the X chromosome. If each parent has a different color variant, the result in furry offspring is mixed coat color. (A calico cat’s white patches are not really white, they are unpigmented as a result of a different gene.)

The real news about calico cats

The reason I know that this is old news is that I wrote about it in 2009, in one of two features on epigenetics I did for BioScience. It was not new news then, either, far from it. But it’s an intriguing everyday example of the random effects of X inactivation and its resultant genomic imprinting, an epigenetic process. I used it for the same reason the Monitor and the Times did: it is striking, and it involves cats and the opportunity for cat photos.

Calico cats. Credit: tanakawho http://www.flickr.com/photos/28481088@N00/380418201/

Calico cats. Credit: tanakawho
http://www.flickr.com/photos/28481088@N00/380418201/

Cat coat color has been under investigation for more than a century. After Mary Lyon’s discovery of X inactivation in 1961, the reason for tortoiseshell and calico coats was clear. In 1999, Lyon herself–by then one of the few Grand Old Women in genetics–made it her opening example in one of her final papers, a brief primer on X inactivation she wrote for Current Biology.

Tia Ghose explains what the work the Monitor was reporting on is really about at LiveScience. It’s a new method for visualizing genes whose activity is shut down in individual cells. The report comes from a paper delivered at the Biophysical Society meeting last week.

Ghose’s piece includes a nice very basic explanation of X inactivation and its results, using cat coats as an example because that’s the example the researchers used. But Ghose notes correctly that the reason for tortoiseshell and calico coats has been known for 60 years.

Blame the researchers?

So maybe we should blame the researchers for giving the Monitor the impression that the reason for calico cats was their discovery? Or was it just that the Monitor writer, Sudeshna Chowdhury, made rookie mistakes: reporting on unpublished work and getting no outside comment. And apparently not reading up on background either.

I don’t know what the Times‘s excuse was. I guess the opportunity to include a cute cat item in its weekly roundup was irresistible. Another item to file under the heading Too Good to Check.

Ghose’s is the piece to read. But it will not, of course, be the one engraved in tablets of stone, even though it is clear about the science and also gets an important episode in the history of genetics right.

Listen, I’m a lifelong cat lover, but it is not the case that when a researcher waves cats in front of a reporter, the reporter must salivate.

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