If you thought the nature/nurture debate was settled, think again. Far from it, even within the scientific community. Are genes the primary determiner of who will get fat over time, is it the sum of their behaviors, or both?
An article this week in Science News reports on a study done by researchers at Massachusetts General Hospital and the Broad Institute (yes, really) in Boston. They looked at over 2 million genetic variants from thousands of people and came up with a way to predict, they said, a person’s likelihood of becoming “obese” (having a Body Mass Index of 30 to 39.9) or “severely obese” (BMIs of 40 or higher). OK, that sounds useful.
But hold on, other researchers said. Behavior can play a big role, too, maybe a bigger one than a person’s genes. One suggested that if a person was told that they were genetically destined for severe obesity, they might give up and not take any preventive actions, like managing their diet.
Others complained that the algorithm failed to identify a significant fraction of those who actually did become severely obese, almost 75% of those in one part of the study group. It even identified some people as having the lowest probability of becoming severely obese, yet they did.
So is this test really all that helpful? I’d have to say not in its current form. I wonder how it would have flagged me. My BMI is a little above 25 and my doctor keeps pushing me to lose a few more pounds. Easier said than done, as you may know. I’ve change my diet and I’m exercising more. I’ve seen some fat disappear but muscles bulk up, too, so I’ve lost fat but not necessarily weight.
That reminds me of something that happened a few years ago. The Air Force tried to kick out an A-10 pilot they said was overweight. Turns out he was a weight lifter and body builder. His body fat percentage was in the low single digits. He was healthy but his BMI was way over the service’s limits. As I recall, the Secretary of the Air Force had to finally weigh in and stop the pilot’s ejection (both puns fully intended).
That story illustrates the objections of some of those scientists. The pilot’s behavior may have trumped whatever his genes tended him toward… or the two may have worked together for his benefit.
So was that study a bad one? No, it wasn’t. While the researchers may have made claims for their algorithm that it couldn’t support, this is one step along a journey. Better studies will look at more gene variants and will factor in behavior too.
Does “person A” come from a culture where people eat a lot of high-fat foods? Factor that in. Does their family live that life, or have they switched to healthier eating habits? Factor that in too. This could be a case where genes establish tendencies but not destiny.
This kind of work defines gaps in scientists’ knowledge that need to be filled in. The study’s main benefit might actually be in having revealed those gaps.
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