Heritability, Inevitability, and Risk for Obesity

We ought to be the masters of our own fate. Pull ourselves up by the bootstraps. Get up and do what needs to be done. And you know what? Most people do their best. However, this little inspirational talk is no substitute for medical facts. And the fact is that obesity is a highly heritable, chronic disease. In fact the heritability of obesity is 70 percent. That’s right – more than two thirds of the variability of BMI in the population is due to individual variance in genetic traits. Not chance. Not environment. Genes.

Scientists have known this for decades.

But once again, wishful thinkers are arguing that genes are not that important. In JAMA Cardiology, Venkatesh Murthy and colleagues have published a new study of the predictive power of genetic risk scores, fitness, and BMI in young adulthood for obesity later in life. They found that a person’s BMI and fitness as a young adult was better at predicting later obesity than genetic risk scores alone.

Duh. Obesity is a chronic disease. It often shows up early in life.

Facts and Spin

In their paper, Murthy et al draw a perfectly reasonable conclusion. “Caution should be exercised in the widespread use of polygenic risk for obesity prevention in adults,” they write. But for the press and the twittersphere, they offer a less accurate account.

“Genetics clearly has some influence, but other factors are stronger,” said Murthy to HealthDay. Unfortunately, that’s not really what this study proved.

Think about it. By the time someone is a young adult with a high genetic risk for obesity, you don’t need a fancy schmancy genetic risk score to figure out that they have genes putting them at risk. Those genes have already been at work, shaping that person’s body composition. People who hit the genetic jackpot for obesity tend to struggle with it for their entire lives.

Murthy et al didn’t prove that genes don’t matter all that much. They proved that for young adults, the expression of those genes is usually already evident. You don’t need a genetic risk score to see it.

A Silly Debate

The argument of nature versus nurture is a silly debate. Both are important. Genes set the table for obesity. Then, the environment serves it up. Most people who are living with obesity did not sign up for it. They inherited it. Through their gene pool and their surroundings.

Yet we all have to wake up every day and decide what to do about the challenges we face. Whether we chose them or not.

Thus, we can accept the scientific fact that obesity is a highly heritable condition without feeling defeated. Yes, it would be nice to be total masters of our fate. But instead, we must face facts and use objective knowledge and curiosity to find ways to live the very best lives we can.

Click here for the Murthy study and here if you want to read how it was spun in HealthDay.

Fate, painting by Alphonse Mucha / WikiArt

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January 9, 2020

One Response to “Heritability, Inevitability, and Risk for Obesity”

  1. January 10, 2020 at 4:33 am, Mary-Jo said:

    Before genetic testing, we learned a lot from doing good medical histories, looking at patterns of disease in families. I always included obesity on my list. I still remember the stunning feelings of release, of self-acceptance that people felt when THEY learned the role of genetics in their obesity. Even in cases of adoptive children/people, I often pointed to the twins studies with similar feelings of appreciation at understanding the reality of obesity. But, then, the bad news. Clearly, people needed ongoing treatment according to their individual, familial, or community circumstances and we could only provide a smidgeon of that because of lack of resources and infrastructure, lack of will and understanding among HCPs, weight stigma, and the constant blathering of exactly the mantras as described above — foci and ongoing discussions on other factors having the MOST influence. Then and now, people, families, and communities were and are often left to deal with their disease on their own. Yes, it’s getting better, but not proportionate to what the evidence shows.