In a recent post, fat fu made one of those observations that’s so fucking obvious I can’t believe I never thought of it, and yet… I didn’t.
And that is: if you have any doubt about whether weight is genetic, try clicking through some pictures of identical twins. Not only are the pairs almost always the same basic size, but they carry their weight just the same way. Apples, pears, hourglasses, beanpoles — regardless of what shape any given twin is, odds are, his or her twin is exactly the same.
We know that every pair is genetically identical. Now, what are the chances that, having grown into adults with separate lives, every pair also has exactly the same eating and exercise habits? I mean, I know twins tend to be similar in lots of ways that seem downright weird to the rest of us, but there’s no fucking way every set of identical twins ends up with the exact same “lifestyle.” And yet, by and large, they end up with the exact same body. Seriously, go look.
Then come back here and try to tell me with a straight face that genes don’t have much to do with it.
I’m so glad you picked up on this. I’d seen studies saying how heritable weight is, but seeing it visually in the twin festival pictures really floored me.
If anyone’s interested in looking at more here’s a whole slew of twin festival pictures. It’s just the same story over and over again. Identical twins are virtually identical in their body shape. (I also am never going to make a peep about anyone being “too skinny” after seeing these.)
And when you say no way they can have exactly the same lifestyle – oh my god yes. Just imagine numerically how closely they’d have had to match their calories in/calories out (the model we’re supposed to accept is all you need to know) over their entire lives to end up with virtually the same size and shape.
I checked out a few pictures of Identical Twins raised apart, too [link]
(not every set of twins on those pages were raised apart, but the similarities between the ones who weren’t are just the same as the ones who were). Check out the twin brothers married to twin sisters!
My sons are identical twins, almost three years old, and it’s been amazing both the differences and the similarities I get to observe in them.
And while sure, I serve them the same foods pretty much every meal, how much of each item gets eaten by which kid is not at all the same. And yet, other than a slight difference that has been present since birth (one simply was born bigger than the other, due to an imbalance in how the placental “goodies” were distributed), their height and weight gains have been consistently matched their entire lives thus far.
This even though one tends more toward stationary activities like reading books or playing with blocks, and the other never walks if he can run instead and hs yet to meet a surface he didn’t want to climb onto.
Oh yeah, no way weight is genetic…. snort!
…holy, you’re right. It’s that sort of headsmack ‘how did I not think of this?’ reaction. Thanks Kate, and fatfu.
I wonder if there are any cases of identical twins where one is fat and the other is thin.
Meowzer, I’d imagine there are, but I would also guess the likely culprit in those cases is an eating disorder/illness/medication that causes one to gain or lose beyond her natural range.
Ariella, I know! Duh!
Thorn, that’s fascinating about your kids. Also kind of blows a hole in the “eating/exercise habits come solely from the parents’ example” theory, doesn’t it?
Oh yeah. Honestly, I could write a dissertation on some of the crazy stuff I’ve seen my kids do that I /know/ neither of us taught them, both eating/exercise-related and otherwise.
A few examples: my kids are complete daredevils (even the bookish one – when we go to the park, he’s climbing stuff the 5-year-olds are wary of), and I was that kid who never so much as climbed a fence. My husband was not as timid as I was, but he was /never/ as reckless as they tend to be.
Also both kids seem to share my husband’s (bizarro, imo) love of jamming their mouths completely full of food. I’ve never done that, and he’d never done that in front of them. And yet, almost immediately after they started eating solid food, I caught both of them doing it at different times. And even now, they will each do it, though they seem to take turns in who is really into it at any given time. For a few months it’ll be B, then he’ll stop and H will start doing it and then a few months later it’ll be B again.
(Honestly, the urge to go all Mad Behavioral Scientist with my very own set of identical twins is a little hard to resist sometimes. grin.)
“I wonder if there are any cases of identical twins where one is fat and the other is thin.”
There have been twin studies done, like this one. Twin studies are done on sets of twins who were separated in infancy.
Even “obesity101″, a “Huzzah!” site for diet drug scams, concedes that: “Twin and adoptee studies indicate that there is a strong genetic basis for obesity. Studies on large populations of adopted children show that there is no relationship between body weight and adoptive parents, but a close correlation with biological parents. Studies on monozygotic (identical) twins show a much stronger correlation in body weight than between other siblings or dizygotic (fraternal) twins. Researchers vary in their opinion on the weight genetics plays in energy regulation, but genetic factors can account for as much as 80 percent.”
Hey, Tigtog and Lauredhel, just FYI, my spam filter caught your comments (b/c of links, I assume), which is why they’re appearing now.
This also explains why I’VE been losing comments. Took me long enough to figure that out.