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The Genetics of Size

Genes can determine a lot in your life, specifically your weight. It’s up to you to figure out your gene code so you can determine what type of life style is best for your body and health.  Beatrice the Biologist, author of DNA IS YOU!, explains the genetics of size. 

As we fight this “war” against obesity, we’re on the lookout for genetic factors that make some people particularly at risk for being overweight. Sometimes I wonder if this information may have an unintended side effect—that maybe some people who are obese might claim there is no point in changing their eating and exercising habits, as obesity is fated by their genes. And the one thing genetics should not do is take away your hope.

Just like you might have a genetic likelihood of developing breast cancer, diabetes, or heart disease, if you know you have a genetic predisposition to be obese, that is not a reason to throw up your hands and say there’s nothing you can do. Au contraire: it means that you have to work extra hard to stay healthy, the same way that someone who is prone to diabetes has to be careful around sugar. I know that doesn’t make it sound fun, and may seem “unfair,” but in genetics there is no fair. There is the DNA you’re given and what you do with it. We all have our DNA annoyances.

Recent studies show that obesity is between 64 and 84 percent heritable, meaning that having obese parents does indeed make you more likely to be obese yourself. Of course, it’s an estimate for now because teasing apart the genetic factors and environmental influences in this case is extremely difficult. Are children of obese parents more likely to be overweight or obese because they are eating the same food and have the same level of activity as their parents? There are a lot of factors to consider.

We haven’t tracked down the exact list of genes that can lead to obesity, but one that looks particularly guilty is called the FTO gene. Certain forms of this gene are correlated with an increase in weight.

The FTO gene codes for an enzyme that modifies DNA, and it seems that in fatty tissues this gene is more active. Looking mighty suspicious there, FTO. Tsk, tsk, tsk. Besides genetics, diet, and exercise, the particular ecosystem of gut bacteria you have can influence how much weight you do or don’t gain from your diet. And what bacteria you have roaming around in there is greatly influenced by what you eat every day. You shape the colonies with every meal you sit down to.

When it comes to the other part of the size of your body, your height, it is about 80 percent genetically determined. The other 20 percent falls under that “environment” umbrella, which can include things like what you eat, what you do, and what your favorite color is (no, not really). A healthy diet while you’re growing is, not surprisingly, important for reaching your full height potential.

One of the genes involved in height determination is named GDF5. This gene has instructions for a protein that serves as a growth factor in bone. But strangely, this gene only seems to affect height outcomes in people of European descent. I have absolutely no idea why this would only be true in one group of people. Perhaps the mutations in GDF5 that lead to the differences just haven’t happened in other groups. Genetics is really weird that way.

Discover more on how genes can affect you in DNA IS YOU! by Beatrice the Biologist


For more on Tips on Life & Love: Why We Gain Weight


Excerpted from DNA is You! by Beatrice the BiologistCopyright © 2019 by author. Used by permission of the publisher. All rights reserved.

Photo by I Yunmai on Unsplash.


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