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“You’re Going to be Fat!”: Genetics & Weight

Over the holidays, I told someone a story about how I was such an obese little baby that my parents called me “the beached whale” (they weren’t being dramatic, either; old Christmas photos show a tiny baby head atop a massive expanse of velour-swathed body). She replied, “Really? Did you know that the fat cells you store as a baby get reactivated and filled in adulthood, making you obese?” And so yet another alleged harbinger of the scary, awful fat got added to my mental backlog of hearsay and headlines.

It’s getting harder and harder to separate the chaff of misinformation from the reality of scientific study these days. How many of the garbled bits of nonsense–”A moment on your lips, a lifetime on your hips”–are grounded in fact, and how many are just oft-repeated falsehoods?

I cannot confirm or deny the baby-fat-cell-storing myth yet (I’ve been researching it all morning and while I’m finding tons of hits, very few are of the scientific, researched, studied kind. Preliminary report says: yeah, it looks like overweight kids may increase both the size and number of their total fat cells, but that happens post-infancy and since adults can manufacture more fat cells also, it is probably not the be-all, end-all of weight prediction).

I would like to talk about what is my very least favorite weight-related assertion, below:

“You will grow up to look just like/be the exact same size as your mother.”

Frankly, it’s off-putting to hear people advising men to scrutinize their female date’s mother to get a “sneak peek” of what the daughter will wind up looking like. It’s sexist (rarely do you hear women advised to do this with male dates), heteronormative (GLBT people are left out of the equation entirely), and frankly dumb–it takes two people to make a baby! Sometimes women look like their dads–perish the thought, I know, but it happens.

Ireland’s Evening Herald Newspaper reported in February, 2010 that findings from the UK’s EarlyBird Diabetes Study, which followed 300 children for 12 years, indicate women with obese mothers are more likely to become obese themselves, but not because of genetics:

[G]irls whose mothers are clinically obese, and boys whose fathers are similarly unhealthily overweight, are more likely to follow suit”¦Obesity would not seem to be down to inherited genetic factors because fat mothers are no more likely to have fat sons and fat dads do not, in general, have fat daughters”¦The study’s director, Professor Terry Wilkin, stated: “The clearly defined gender-assortative pattern which our research has uncovered is an exciting one because it points towards behavioural factors at work in childhood obesity.” (emphasis added)

The Herald expounds on the solution for obesity, then, as over-riding bad health habits learned from one’s same-gender parent, which is an entirely legitimate tack to take, though I wish they had also covered socioeconomic and educational factors.

I am still not convinced that genetics play no role in one’s weight, particularly since the above study was dealing particularly with obesity, not with classifications like “overweight” that apply to people above their proscribed BMI range, but not yet in the obese range.

I found a news release concerning a 2007 study from the Joslin Diabetes Institute (affiliated with Harvard Medical School), which was presented at the American Diabetes Association’s (ADA) 67th Annual Scientific Sessions in Chicago. Researchers found that certain genes were associated with weight, and made one particularly interesting discovery:

An SNP in one particular gene, T-box 15, which regulates the development of cells and cellular growth in fat tissue, showed a strong correlation with both higher body weight and bigger waistlines. While this effect was observed in the entire sample of individuals, it was much stronger in women. The women with the risk variant were three times more likely to be overweight than women who did not have the variant.” (emphasis mine)

I am not a scientist, so bear with me if my analysis is foolish (and feel free to lend your perspective or correct any false assumption I make): In the UK’s EarlyBird study, researchers found that women with fat mothers were 10 times more likely to be fat themselves, while sons with fat fathers were only six times more likely to be fat.

Why the stronger correlation between mothers and daughters? Could it be that, if a fat mother passes her fat-expressing T-box 15 gene to her son, he is less likely to be affected by it, whereas a daughter who receives the gene is more likely to wind up overweight? That would lend a very small bit of credence to the “You wind up as large or small as your mom” trope.

I don’t know, and I’ve read a lot of contradictory things today, but I can conclude at least this: the blithe saying, “You’ll look just like your mom” is stupid. Instead, people should start saying, “If your mom possesses a gene that handicaps fat regulation and passes it on to you, and your body expresses the gene, and you have the same eating and exercise habits as your mother, and there are no other genetic or environmental factors interfering, you will look just like your mom.”

This post doesn’t even begin to cover the topic of fat-shaming or how hysteria around childhood obesity (really, obesity in general) has been building to an unhelpful fever pitch. But I do think the casually tossed-off, uninformed references to weight, which I hear all the time, are contributing to fat-misunderstanding culture in a big way.

2 replies on ““You’re Going to be Fat!”: Genetics & Weight”

I was thinking my tendency to look more like my mom would be caused in part by us having similar ways of spending our shared time and similar eating habits, but actually in my experience that wasn’t the case–we don’t actually have similar eating habits, nor do we spend time doing the same things. And my eating habits aren’t like my dad’s either, though our body types are more similar. So I guess my not-super-helpful take on this is that the claim that a woman will look like her mother is dumb.

Here’s my completely non-scientific study: my husband is adopted.  His adoptive parents have two biological children (so, three children total and two parents).  The four who are related biologically are all tall and thin.  My husband is shorter than they are (average male height, but shorter than they are) and heavy.  He was adopted as an infant, raised with the same eating habits as his siblings, but clearly something about him is different.  My take is that weight has a lot to do with nature and some with nurture, but I’m not claiming to be a scientist or anything.

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