BBC recently published a story titled “Skinny genes the ‘secret to staying slim,’” which seems to push the idea that being skinny or fat is largely the result of genetic composition. The story opens with: “Scientists say they have discovered the secret behind why some people are skinny while others pile on the pounds easily.” The problem is that when you dig into the details of the article, this isn’t true. The original research doesn’t assign genes as a cause of obesity but, rather, as a heritable risk factor.
Association does not mean causation.
I write a lot about diet, exercise, weight loss, and body composition. I’ve also worked for almost two years in a mitochondrial bioenergetics laboratory that investigates the molecular processes behind the development of obesity and Type 2 diabetes. Yet, I still think of myself as possessing only a basic knowledge of obesity genetics. So, how did a journalist and their editor handle the task of analyzing the significance of a genome-wide investigation into the heritable risk factors for a lifestyle disease? But, of course, the purpose of the story doesn’t seem to have been to educate; it’s more about drawing in readers.
Science journalism takes some liberties in writing “scientists say” and “researchers concluded,” even when this is not necessarily the case. People trust scientists and doctors and, really, any trained professional in a given field. It’s much easier to sell a story if you put the words in the mouth of a scientist.
Although I disagree with the way science news hits the mainstream, we do need a way to educate people about the latest findings in health science research. Time and again, science journalism takes published research and repackages it into something marketable. And while it’s promising that the general public has taken such an interest in science, to the media, it’s just another product to push.
The BBC article was based on an original scientific article published in PLOS Genetics that suggests the findings are “a valuable resource on which to study resistance to obesity in an increasingly obesogenic environment.” When examining the “genetic architecture” of body weight, there is “evidence of association.” But here’s the problem: Association does not mean causation.
The researchers examined the genetic composition of thousands of people who represent the entire spectrum of human body shapes. This included both obese people and “healthy thin” people, as well as people who fall into the normal range of body weights in between.
The major finding of the study was that certain genes are more common among naturally skinny people, much like there are certain genes more common among overweight and obese people. Based on these results, genetic composition can be used to assign a statistical probability of being skinny and a statistical probability of being fat.
Your genes, however, do not cause you to become fat or thin. A person’s actions, and other physiological factors, are still a major determinant of the outcome. It’s just that certain people will find it easier to stay slim than others.
It’s like getting a tan. Some people have fair skin and have to spend several days in the sun for their skin to noticeably darken. Others, however, can spend 30 minutes outside and come back a shade of bronze. Genetic makeup determines how easily a body produces melanin, but genes do not cause skin to tan—exposure to UV radiation causes that.
Science journalism has been following a dangerous trend of insinuating that people are less responsible for our health than we think.
The root cause of an increase in obesity worldwide is an increased prevalence of sedentary living and changes in eating patterns globally. At the population level, the idea that genes are the primary cause of obesity is not scientifically valid. Of course genetic makeup contributes to individual health. But there is also overwhelming scientific and clinical evidence to support the idea that diet composition and physical activity levels can be used to drive or combat obesity. Although it may not be exciting news, reporters should be focusing on the impact of changing lifestyle habits on global health.