Lifestyle Economics Blog

The Fat Lie - the real cause of the rise in obesity

Obesity prevalence has increased sharply in Britain since the 1970s. Many public health campaigners portray Britain’s obesity ‘epidemic’ as being caused by the increased availability of high calorie foods, sugary drinks and larger servings in restaurants. This view has been reflected in television programmes such as The Men Who Made Us Fat (BBC), which focus on the supposed rise in calorie consumption while paying little attention to the other side of the equation: physical activity. Some campaigners explicitly dismiss physical activity as a factor. For example, Aseem Malhotra, science director of Action on Sugar, says that ‘it’s time to bust the myth of physical activity and obesity’.

Today, the IEA has released a briefing paper that demonstrates that this conventional wisdom has no basis in fact. If people are ‘being bombarded every day by the food industry to consume more and more food’, as some claim, then the industry has failed. Consumption of calories - and of sugar and fat - has fallen significantly while obesity rates have risen.

The Department for Environment, Food and Rural Affairs (DEFRA) has carried out annual surveys of the British diet since 1974. These surveys are based on diet diaries compiled by a cross-section of the public and are supported by till receipts (DEFRA, 2013). Shown in the graph below, these data indicate a significant decline in daily per capita calorie consumption in the last forty years, from 2,534 in 1974 to 1,990 in 2012. This represents a decline in energy consumption of 21.5 per cent.

This is corroborated by the National Diet and Nutrition Survey (NDNS) which began in the 1990s, the results of which can be compared to the Dietary and Nutritional Survey of British Adults which holds data for 1986/87. These surveys collect data for food and drink consumed inside and outside the home. Shown below, they indicate that average calorie consumption has fallen by 9.8 per cent for 19-64 year olds since 1986/87.

Both datasets also show a decline in per capita consumption of carbohydrates (including sugar) and fat (including saturated fat).

It is clear that average body weight has been rising for decades while average calorie consumption has been declining. Assuming that the laws of thermodynamics are correct, there can be only one explanation for this: Britons are, on average, burning fewer calories than we used to.

This should not be surprising. 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. Add to this the ubiquity of labour-saving devices and it is clear that Britons today have less need, and fewer opportunities, for physical activity both in the workplace and at home.

Obesity features so often in the media that it is surprising that the data shown in this briefing paper are not better known. The myth that Britons are consuming more and more food has persisted for the following two reasons:

Firstly, there is a tendency to import narratives from the USA where, in contrast to the UK, calorie consumption rose in line with obesity rates for many years. This dual trend had come to an end by 1990, however, and the role of chronic physical inactivity is beginning to be acknowledged as the driver of rising obesity in the years since.

Secondly, the food supply is a more inviting target for health campaigners than the sedentary lifestyles of the general public. A war against ‘Big Food’ requires no stigmatisation of individuals (other than the individuals who work in the food industry) and there are a readymade set of policies available which have been tried and tested in the campaigns against tobacco and alcohol. Instigating such a war, however, requires the public to believe that food companies have acted unscrupulously by stuffing unwitting consumers full of calories, forcing large portions upon them and spiking their meals with sugar and fat. The data shown in this paper are clearly not helpful to that narrative.

Such is the sensitivity of the public health lobby to this sort of information that when two researchers published a paper showing that sugar consumption had been declining in Australia for thirty years while obesity had been rising, they were branded ‘a menace to public health’ and investigated for scientific misconduct. They have since been exonerated, but the title of their study - ‘The Australian Paradox’ - highlights how deeply rooted is the belief that obesity can only be the result of increased sugar and/or calorie consumption at the population level. As the evidence from the UK - and, in recent times, the USA - shows, it is no paradox at all.

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