George Monbiot has written a curate’s egg of an article for the Guardian on the subject of obesity. Struck by the near-total absence of fat people in a photo of Brighton beach in 1976, he wondered whether the rise of obesity in the intervening years was the result of more calories in or fewer calories out.
What he discovered came as a shock to him. His first revelation will be no surprise to readers of this blog: calorie consumption has fallen over time. Thanks to the National Food Surveys, we have a treasure trove of information going back to 1940. It shows that the average Briton was consuming more than the modern recommendation of 2,500 calories a day during the war. This rose after 1945, peaking in the 1960s, and falling thereafter. Average daily calorie consumption fell from 2,850 in 1970 to 2,560 in 1980. By 2011, it had dropped to 2,269. Figures from the National Diet and Nutrition Survey, which began in the 1980s, tell much the same story.
These surveys have raised concerns about mismeasurement. We know that people under-report what they eat and that fat people under-report more than thin people. In 2016, Public Health England hired the Behavioural Insights Team to look into this. Sure enough, they found evidence that people under-reported calorie intake and that the scale of under-reporting had risen over time, but even after correcting for this, they found that we are consuming fewer calories than we did in the 1970s.
All the evidence points in the same direction. Average calorie consumption – and, indeed, sugar consumption – is lower today than it was in the 1970s when obesity was relatively rare. The only way to deny this is to dismiss decades of research as worthless rubbish. That is not a good look for an empiricist and it is to Monbiot’s credit that he does not do so.
If we are not consuming more calories then the rise of obesity must be due to us burning fewer calories off, right? Not so fast, says Monbiot. He offers evidence that children are doing just as much exercise as ever and that people in poor countries burn the same number of calories as people in rich countries.
So what is the answer? Alas, this is where Monbiot’s article descends into gibberish. If you’re familiar with his oeuvre, you won’t be surprised to hear that the blame lies with those nasty corporations. They use advertising to ‘overcome our resistance’. They ’employ an army of food scientists and psychologists to trick us into eating more than we need’. They ‘discovered our weaknesses and ruthlessly exploit them.’
This is all standard Guardian banter but it doesn’t make any sense in the context of Monbiot’s article. It is almost as if – perish the thought – he decided what his conclusion was going to be before he began his research.
Even if everything Monbiot says about ‘Big Food’ is true, even if he is right when he says that ‘the opportunities to load our food with sugar have boomed’, we are still faced with the inescapable fact that we are consuming less sugar and fewer calories than we did in the glorious summer of 1976. As far as I can tell, Monbiot does not subscribe to magical thinking about particular types of calorie. His explanation therefore explains nothing.
So what is the real answer? There are factors that Monbiot does not mention, such as the rise of central heating and the decline of smoking, which are likely to have had some effect, albeit only on the margins. It is possible that future research will find that some unsuspected biological factor has also played a role. And it is important to remember that averages do not tell the whole story. It would be an ecological fallacy to assume that everybody is eating less just because average consumption has fallen.
Nevertheless, it is puzzling, to say the least, that the rate of obesity could rise so sharply if calorie consumption has fallen and people are as physically active as they have ever been. But this is where Monbiot makes his mistake. Physical activity has declined and his slivers of evidence to the contrary do not stack up against the facts. Public Health England says that levels of physical activity have dropped by a quarter since 1961. The World Health Organisation says that western countries have seen ‘decreased physical activity levels due to the increasingly sedentary nature of many forms of recreation time, changing modes of transportation, and increasing urbanization.’ Harvard School of Public Health says that: ‘Physical activity levels are declining’ and that ‘this decline in physical activity is a key contributor to the global obesity epidemic’.
Physical activity is not always easy to measure and it is often confused with leisure time exercise, but there should be little doubt that we are burning off fewer calories than ever in our day to day lives.
Unsurprisingly, people who drive to work are fatter than those who go by foot or by bicycle. And when we get to work, we are more sedentary than ever, as Tim Olds notes:
In the 1960s, half the jobs in private industry in the United States required at least moderate-intensity physical activity, compared to less than 20% today.
Work in factories and farms has given way to office work, and that has amounted to over 400 kilojoules less each day that adults expend at work. This difference alone results in a weight increase of about 13 kilograms over 50 years, which pretty closely matches actual changes in weight.
Only 18 per cent of British adults report doing any moderate or vigorous physical activity at work while 63 per cent never climb stairs at work and 40 per cent spend no time walking at work. Outside of work, 63 per cent report spending less than ten minutes a day walking and 53 per cent do no sports or exercise whatsoever.
This trend is confirmed by the National Food Surveys, which occasionally allude to the fact that the rise of office work resulted in people not needing to eat so much. As early as 1962, they reported that ‘energy requirements have decreased in all regions … The decrease in calorie requirements is greatest in Classes A2 and B, and is partly explained by the increasingly sedentary nature of their occupations’. In 1971, they mentioned the ‘continuing decline in energy needs as work becomes less strenuous.’
On average, declining energy needs have resulted in declining energy consumption, but not for everybody. Hence obesity. It is easier than ever to get fat, not because we are eating more but because physical activity has been engineered out our lives. It is trivially true to say that obesity is caused by eating too much, but in relation to what? If we want to understand what has changed at the macro level in the last fifty years to drive up rates of obesity, we must first acknowledge that ‘calories in’ have not gone up. And once we accept that, there is only one credible explanation left: ‘calories out’ have gone down.