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The Salt
9:59 am
Wed October 5, 2011

Thin Moms And Dads Pass On 'Skinny Genes'

We inherit the darndest traits from our parents. My mom bequeathed to me that funny leg-shake she does when she's sitting. She also seems to have passed along a quick (but ... hmm ... endearing?) temper. And in the "thanks-for-that" column? Well, I'm on the skinny side. And so is she.

Our mother-daughter likeness isn't so unusual. Turns out, the "inter-generational transmission of thinness" is real. Thin parents appear to pass on "skinny genes."

Researchers at University College London have published the results of a five-year study evaluating this association in body weight in 7,000 families with young kids and teenagers. They found that parental weight strongly influences thinness in children.

For instance, a child who has two thin parents was twice as likely to be thin compared to a child of parents who were in the normal or upper half of the weight range.

So is it genes or perhaps shared behaviors that may explain this phenomenon?

I put the question to Jane Wardle, one of the authors of the study, which appears in Archives of Pediatrics and Adolescent Medicine. "Asking this question sets up a false dichotomy," Wardle explained to me, because genes influence our behaviors.

"The way the weight-related genes work," Wardle says, "is that they tend to give you either a big appetite or a small appetite."

Though this study did not analyze genetic make-up of the participants, researchers know from previous studies that parents transmit to their children multiple genes that influence weight.

This study did not evaluate whether the likeness in weight holds up in adult life. So maybe my mom and I won't end up being the best example here.

When I told my mom about the study, she laughed, then asked: "Who turned those (skinny) genes off ?!" She didn't want me to blab about her weight, but let's just say that around age 60, the numbers on the scale started to creep up — just a little bit.

We both noticed long ago that our genes are certainly not completely deterministic of waistlines. So we both still exercise and try to eat well.

Previous studies have found that obesity runs in families, so maybe it's not a huge leap to think of thinness being hereditary, too. And unraveling the mysteries of why we do what we do often goes back to genes. A previous
study
from UCL a few years ago showed that parents who are picky eaters — who have an aversion to trying new foods — often give birth to ... you guessed it ... picky eaters.

The researchers estimate that 75 percent of kids' proclivity towards "picky-eating" habits was linked to heritability — or genes.

Copyright 2011 National Public Radio. To see more, visit http://www.npr.org/.