Genetics and obesity in the media

Should there be a tax on sugary drinks? (and should Journalists try and be a little more constructive when writing about obesity in national broadsheet newspapers?)

The column inches dedicated to sugar, its potential taxation, and obesity are expanding almost as rapidly as those around our waistlines. Is our small niche in the study of obesity of any relevance?

As many have written before, obesity is in one sense a very simple problem – we consume more calories than we burn – but the reasons why some of us are more out of balance than others are multiple and complicated. Academics from many fields other than our own have something to say on the subject – sociology, education, sports science, psychology and economics, in addition to public health and Medicine. In another sense the obesity crisis is a dramatic success story – we are no longer burning 1000s of calories down mines, in dockyards, or on farms, and the motor car and washing machine have improved standards of living. But we’ve overshot and now children are leaving primary school unable to chase a ball, and the firebrigade had to be called >2000 times last year to rescue severely obese people from their homes, according to one newspaper report. Cancer and heart disease are also symptoms of social and economic progress – because we are living longer and so have more chance of developing them – but no one would argue we shouldn’t take public health measures to reduce those diseases.

We have some expertise in only one of the many factors that contribute to our expanding waistlines – the genetics of obesity (more accurately, the genetics of variation in BMI). “How can obesity be genetic, there didnt used to be fat people?” cry many folks; “there was no food in the war and I have the same genes as my grandparents!” was another comment after the identification of the first common “fat gene” . Others have been more blunt and often downright hurtful to overweight people who, unless they are sumo-wrestlers or Robert de Niro auditioning for Raging Bull, presumably didn’t set out to deliberatly pile on the pounds. Well educated journalists seem especially prone to fat bashing, and seem very certain of themselves when they strongly imply that people would lose weight if they wanted to, although also, in one piece, suggest they shouldn’t jog in parks – see articles by Giles Coren and Robert Crampton in The Times. Newspaper columnists are paid to provoke us (I have taken the bait), but substituting the word “long term-unemployed” or “gay” for “fat” into some of what they write is revealing. (I chose “gay” and “long term-unemployed”, because I suspect they are things you can change just as easily as you can lower your BMI substantially if you’re obese (without resorting to bariatric surgery). The unemployment analogy also works well because unemployed and obese people are often perceived as lazy, which is to ignore how the environment influences both – the economic climate, and the availability of food wherever we look, respectively.

The evidence is overwhelming that genetic factors influence why some of us expand more than others in today’s world of limitless food supply – see this twin study and this study of genetic relatedness for two examples. And if there was still doubt, scientists have found many regions of the genome associated with BMI – there are now nearly one hundred regions of the human genome linked to variation in BMI, as this paper , in which we had a minor role, shows.

Are genetic studies of any relevance to the almost daily debates about obesity, including the sugar tax? What we do know about the genetics of obesity fits very well with the concept that subconscious decisions to consume food are very important. The largest genome wide study identified genes expressed in the brain far more than we’d expect by chance. And other studies show that a small proportion of people with a very high BMI since childhood have an almost entirely genetic explanation – such as the presence of a mutation in the gene that encodes their MC4R protein, that means they never feel satiated.

The argument that people should be left alone to decide what to eat for themselves is facile. No one is claiming that people shouldn’t take some individual responsibility, but then no one is deciding to obtain a BMI of 45kgm2 by 45 years old. Public health measures to reduce smoking worked. And now genetics show that some of us are more susceptible than others to today’s calorie dense, exercise unnecessary environment, strongly suggesting that measures to nudge us subconsciously in the right direction, will help.

The Mexican sugary drink tax has reduced consumption, although it is too early to tell if this equates to lower BMIs. But there is randomised controlled trial evidence that when people, including children, consume fewer calories in the form of, for example, artificially sweetened drinks instead of sugary drinks, they don’t seek out replacement calories later. Just as eat-all-you-want restaurants use smaller plates, and we’ve never heard of someone finishing their meal and thinking “Aha, I need to go and eat more in order to become obese”.

Is a calorie of sugar the same as a calorie of broccoli? We’re not experts in diets or metabolism, or indeed the effect of broccoli on your microbiome, but we know which one is more likely to end up in your mouth. And we don’t need academics to prove that. Supermarkets (overall a force for good, especially women) have trialled ways to sell more food for decades. They’re experts at selling us food we didn’t go in the shop to buy. Selling more food by placing certain products in certain places relative to our eyeline is a science in itself (albeit not many studies are written up), and is based entirely on our subconscious decision making processes. (test it yourself by shopping on separate days before and after a big meal, then checking the bill , and indeed the vouchers you recieve to buy more). Many boxes of vitamin-fortified, whole grain, half price, but 35% sugar, boxes of cereal later, and the genetic studies back up what supermarkets have known for a long time. And which products do they place nearest the checkouts ?

We suspect a sugar tax on its own won’t make much of a dent to our waistlines, at least not whilst Coca Cola is allowed to sponsor the LondonEye, but intervening in some form is justified. And in case you thought we’d lost our sense of scientific rigour, we’d advocate a decent chunk of research money going to statisticians to study the outcomes of any sugar tax, (thats not us, we just find the genes), and even considering a dose response formula – randomise towns and cities to different tax levels and study the outcomes.

Meantime, we’d suggest well educated journalists use their high platform to be a little more constructive than writing Katie Hopkin’s style laments to
“not spare the blushes of pie-guzzling flesh mountains”

Tim Frayling June 2016