Saturday, 9 April 2016

So you're fat? It's not your fault you know.


Or so says the Government's obesity 'tzar', Susan Jebb, professor of diet and population health at the University of Oxford:

"Obesity has increased so greatly over the last few decades. That's not a national collapse in willpower. It's something about our environment that has changed," she said.

"You need in some cases a superhuman effort to reduce your food intake. Is that their fault? I don't think it is."

Let's get one thing out of the way. This isn't complete bollocks but the environmental change that Professor Jebb thinks is the problem, isn't the cause. No-one is disputing that there are genetic differences in propensity for weight gain, we've known that for decades. Nor is anyone disputing that some people have less (or more) willpower than others, that socialisation - typically parental attitudes and diet - is important and that there is a mountain of misinformation about health and diet.

The problem is that our increased rates of obesity didn't take place in an environment of rising calorie consumption. And whatever fad or fancy you subscribe to in this debate, it is indisputable that the reason for weight gain is consuming more calories than you use. Any sort of calorie, your body doesn't make any distinction between sources. There isn't such a thing as an unhealthy food, just unhealthy diets.

Two things have changed. Firstly (and we'll get this one out of the the way) we are, on average, older and older people are, again on average, fatter than younger people. This isn't a problem (unless you see sub-optimal birth rates as a problem).

The other change is that we live a vastly more sedentary life than we did three or more decades ago. Coca-cola even ran an ad featuring these differences (and, as ever, ad men were spot on). And the environmental change is striking:

In 1970, 2 in 10 working Americans were in jobs requiring only light activity (predominantly sitting at a desk), whereas 3 in 10 were in jobs requiring high-energy output (eg, construction, manufacturing, farming). By 2000, more than 4 in 10 adults were in light-activity jobs, whereas 2 in 10 were in high-activity jobs. Moreover, during the past 20 years, total screen time (ie, using computers, watching television, playing video games) has increased dramatically. In 2003, nearly 6 in 10 working adults used a computer on the job and more than 9 in 10 children used computers in school (kindergarten through grade 12). Between 1989 and 2009, the number of households with a computer and Internet access increased from 15% to 69%. Other significant contributors to daily sitting time—watching television and driving personal vehicles—are at all-time highs, with estimates of nearly 4 hours and 1 hour, respectively

This isn't about whether we do that half hour of 'physical activity' we're encouraged to partake of - that's a red herring. This is about the totality of our lives, about the elimination of activity from more and more tasks. Think about putting a screw in - we've now replaced the screwdriver requiring a vigorous physical act with a power tool. Multiply that across everything from beating eggs through to buying a weeks groceries and we've a striking picture of decreased activity.

We can't deal with this problem (although it isn't really a problem, is it) by taking up jogging. Nor can we wind back from the efficiency and productivity gain - in every aspect of life - that technology brings. And we can't force people to take up a sport, go for bracing country walks or sign up to a gym - not when there's a great Netflix box set just out. We can begin to design environments that promote movement - not just at work bearing in mind that this takes up less than a fifth of a typical week. Plus we can (since we're talking about weight here) reduce our total calorie intake.

Indeed we have reduced how much we eat:

So, if we want to do something about the 'obesogenic' environment, we don't do it by banning fast food shops, taxing sugar or forcing children to eat almost completely nutrition-free salads for dinner. No, we do it by designing in physical movement - stairs instead of escalators, public transport instead of cars, proper going-out-of-the-office lunchtimes. A thousand and one little bits of change that mean people move a bit more.

It might just work. What I know for sure is that Professor Jubb's anti-food, anti-pleasure agenda won't make a jot of difference (except to raise the ire - and blood pressure - a people who want a little pleasure in their lives). And, remember, you all have agency - you can choose. You don't have to be fat. If you are, it really is mostly down to your choice.



John Leach said...

You claim two things have changed: we're getting older and we're getting more sedentary.

But you also show that we've reduced our energy consumption. What's your explanation for that? Is everyone just hungrier now then? Or is willpower more potent today than it was back then, like marijuana?

The answer is that when we get older, or more sedentary, we don't desire to eat as much food. Because the human body is not a simple combustion engine.

What's missing from your data is the proportion of our energy consumption that is from fat vs. from sugars, and that has changed quite a bit. And is important.

Your body does make distinction between sources of energy, the distinction and effect just isn't simple. Because we're not simple.

Dan said...

If you want an answer to this question, you have to look at what we are spending most of our energy on. To a biologist like myself, the answer is pretty simple: we're mammals, we spend most of our food intake maintaining our high body temperatures.

So, what has changed in the last thirty years or so that could impact on our energetic costs? Easy: central heating.

When I was growing up in the 1970s, bedrooms weren't heated and houses were single-glazed. I remember my father going round all the windows in the morning with a cloth, wiping away all the water that had condensed on them over the night. The only house heating we had was two gas fires (later supplemented with a small gas burner at the bottom of the stairs) and that was it for heating a three-bed semi. There was an electric heater in my bedroom, which I wasn't allowed to use because it cost too much to run.

Now I live in a terraced house with double glazing, and the house temperature never drops below 18 celcius. I never see ice on the insides of the windows like I did when I was growing up, and my bedroom is only cool because of the thermostatic valve on the radiator.

I'm warmer, but have to watch my weight because the warmer housing means I expend much less energy simply keeping warm. That's why people are getting fatter. Simple.