Lifestyle Economics Blog

Physical inactivity and obesity - don't be fooled

As has been widely reported in the media today, an opinion piece in the British Journal of Sports Medicine seeks to overturn a mountain of evidence - and the laws of thermodynamics - with the claim that "physical activity does not promote weight loss". One of the authors of the editorial, Dr Aseem Malhotra of the pressure group Action on Sugar, has a track record of misinforming both the public and politicians about diet and obesity. In the past, he has blamed obesity in the UK on High Fructose Corn Syrup, despite this product being practically non-existent in the EU, and has attributed every single death from cancer, heart disease and diabetes worldwide to poor diets. In 2014, an article he wrote for the British Medical Journal was investigated and corrected as a result of extreme and insupportable claims made about the safety of statins, with the investigation revealing that Malhotra had ignored the concerns of peer reviewers. Moreover, Action on Sugar's briefing papers are riddled with inaccuracies.

Dr Malhotra's latest opinion piece is, perhaps, the most controversial yet. He first denies that physical activity is linked to obesity and then denies that there has been a decline in physical activity in Britain since the mid-1960s. The first claim is contrary to the opinion of almost every expert in the field. Public Health England, for example, says: "The link between physical inactivity and obesity is well established." Countless studies have shown the value of physical exercise in both weight loss and healthy weight maintenance.

The second claim - that "there has been little change in physical activity levels in the Western population" in the last thirty years - flies in the face of lived experience. The last thirty years have seen a continued shift from manual labour to office work, as well as the rise of computers, video games, labour-saving domestic appliances and a continued increase in car ownership. The World Health Organisation acknowledges 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."

Lived experience is confirmed by empirical data. Public Health England says that levels of physical activity have dropped by a quarter since 1961. The proportion of children who walk to school has dropped from 70 per cent in 1980 to less than 50 per cent today. And, as I explained in my IEA report The Fat Lie:

'The transition from manual labour to office work saw jobs in agriculture decline from eleven to two per cent of employment in the twentieth century while manufacturing jobs declined from 28 to 14 per cent of employment. Britons are walking less (from 255 miles per year in 1976 to 179 miles in 2010) and cycling less (from 51 miles per year in 1976 to 42 miles in 2010). Only 18 per cent of 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.'

The Telegraph reports that 'Dr Malhotra said US data which tracked obesity and activity levels found little change in activity levels over two decades, while obesity levels soared.' This, again, is the very opposite of the truth. A recent study from the US concluded that the proportion of American men who engage in no leisure-time physical activity whatsoever soared from 11 per cent in 1988 to 44 per cent in 2010. For women, the rate leapt from 19 per cent to 52 per cent. The study authors noted that during this period "Average daily caloric intake did not change significantly."

Against this huge weight of evidence, Malhotra et al. provide just one solitary reference to support their case. Published in 2013, it is an opinion piece - not new research - and has been widely criticised by experts in the field. It controversially claimed that 'the "labour-saving culture" was fully in place by the 1960s-70s' thereby implying that physical activity has not declined since. This view has been challenged by, for example, Blair et al. who provide evidence that weekly energy expenditure declined by 1,800-2,500 calories between 1971 and 2006 in the USA. The original article and the responses from Blair et al. and Hill and Peters are worth reading by anybody who is interested in the subject. In sum, the sole article that Malhotra cites as proof of his case is little more than a contentious and obscure academic detour.

Claiming that there is no link between inactivity and obesity is the equivalent to claiming that the Sun revolves around the Earth. The multi-million pound diet industry makes its money by pretending that there is more to weight loss than calories in an calories out. There is not, and a one page editorial in a niche journal is not going to change that. Moreover, there is an enormous amount of evidence showing that (a) people are living more sedentary lives than ever before, and (b) people are burning fewer calories than ever before. Unsurprisingly, we have become fatter.

Why this desperate attempt to persuade the public that black is white? It is difficult to imagine obesity campaigners engaging in this level of denial if there was a physical inactivity industry against which to crusade. Since the government is not prepared to force people to exercise, campaigners have to focus on what they can change by legislation. This means blaming everything on the food supply with a view to taxing, banning and restricting. Their conclusions, which have plunged to absurd new depths today, are driven by the need to absolve individuals of responsibility whilst justifying state intervention. They provide clickbait for newspapers and ammunition for pressure groups, but such irresponsible and scientifically illiterate messages should be ignored by all thinking people.

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