Tuesday, 18 July 2017

Obesity: It's not just diet.

BBC Radio Jersey reports that:

A food and nutrition strategy is being launched in Jersey today by the States. The strategy includes plans for sugar taxes, free school meals and new rules for fast food sites. Poor eating habits in Jersey could be costing the health service more than £40m a year, health experts believe. The States of Jersey is launching a new diet and nutrition strategy and experts are warning of the consequences of a bad diet.

There are four pieces of evidence that seem to support this view that eating is the root cause:

  1. Food prices have fallen substantially over the past 30 years;
  2. Real food expenditure (the amount we spend on food, accounting for inflation) has increased;
  3. Expenditure on some types of calorie dense foods, such as fast food, eating out, ready meals, confectionery, and soft drinks has increased; and
  4. There has been a sizeable increase in calories available, according to aggregate data on food available for human consumption (the total amount of food produced, including imports and excluding exports, minus food used for animal feed, agriculture, industrial uses, and waste)
And yet as BBC Radio 4’s Analysis explained, the big picture regarding food is far from the simplistic one about poor eating habits. In fact as the graph above shows, calorie input has steadily gone down over the past 30 years.

In the programme, “Is Work too Easy?”, Michael Blastland asked if it's desk-bound work, rather than over-eating, which is making more and more of us obese.

“He hears about remarkable research which, despite received wisdom, suggests that people in the UK have reduced their calorie intake. However, they are expending far less physical energy, particularly because of new patterns of work which now require little if any bodily exertion. Michael examines projects to change individual behaviour such as corporate wellness programmes and altering office layouts - but finds it's going to be a tough sell.”

The main research in question is a robust study, carried out by Dr Melanie Luhrmann from the Department of Economics along with Professor Rachel Griffith and Dr Rodrigo Lluberas of Royal Holloway.

It has revealed the surprising fact that while obesity rates have almost trebled, our actual calorie intake has fallen by around 20 per cent compared to 30 years ago.

In their paper, entitled Gluttony and sloth, Rachel Griffith and Melanie Lührmann examined the statistical evidence two different ways, and both came to the same result.

They note that “Surprisingly, we find that total calories purchased have declined substantially over the last three decades. We distinguish two periods: 1980-2007, when food prices were falling; and after the Great Recession (2008-2013), when food prices increased worldwide and real incomes fell for many people. Table 1 (see top of this blog) shows the continuous decline in mean calorie levels regardless of food price changes. In the paper we show that this decline is not just occurring at the mean, but also across the distribution.”

And they note that in fact the shift away from often fattening homemade food of past decades has actually moved towards more expensive food which we eat less of. Although there is a tendency to eat more pre-packed food, home cooking was not necessarily less calorific.

“One important reason for this decline in calories, contemporaneous with a rise in real expenditure, is that households have shifted away from homemade food, and toward market-produced food (for example by shifting from food at home towards eating out), which is more expensive. The other reason is that there has been a decline in the purchase of some high calorie foods for consumption at home, such as red meat, full fat milk, butter, and jams, and this more than compensates for the increase in calories from foods and drinks outside the home.”

And they comment:

“This leads to a puzzle: if people are buying fewer calories, and so presumably consuming fewer calories, how do we explain the rise in obesity? Weight gain arises from a caloric imbalance; that is, when more energy is consumed than expended. If there has been a decline in total calories purchased over the past 30 years, could an even greater decrease in levels of physical activity explain the rise in obesity?”

And indeed this is where the cause comes in.

Dr Melanie Luhrmann says: "Our research shows that decisions over work and food demand are related. First of all, because individuals that work substitute more towards market-produced food, for example, towards processed foods and eating out. Secondly, weight gain arises from a caloric imbalance, meaning if more energy is consumed than expended. Hence, both calories and physical activity are important in explaining the rise in obesity. People have adjusted their calories downwards, but not enough to make up for the sizable decline in physical activity. Part of this decline comes from reduced activity at work. So we should take into account the link between work and calories when evaluating policy interventions aimed at reducing obesity."

They look at the data from the Labour Force Survey, a nationally representative survey of individual work patterns. This shows that there have been significant changes to the nature of work. England has seen a marked shift over the last thirty years towards less strenuous and more sedentary occupations. In particular, there has been a substantial shift towards sedentary service sector jobs.

“The fraction of men working in strenuous occupations has declined by 8% from 1981-2009, and those working in sedentary jobs has increased by over 11%. For females the decline in strenuous occupations is over 13%, with an increase in both moderately strenuous and sedentary jobs.”

“The change in work patterns has had a big impact, because work accounts for a large share of people's time. In addition, labour supply behaviour has also changed, with different trends for males and females. Female labour force participation amongst 25-64 years olds has increased from 55% to 69% between 1980 and 2009, with particularly strong increases among younger women (aged 25-39)”

Statistics show that adults of working age may spend as much as 50% of their waking hours in the work environment. So occupational physical activity is a potential determinant of total daily energy expenditure. It has been found that professional and white collar workers have taken less steps (measured by pedometer) and have lower volumes of occupational physical activity than blue collar workers.

And there is also what they call “slothing at home”:

“Over time, working women have increased time in market work, and so have reduced the time they spend on other activities from 60% to 54%. They have also reduced the amount of time in strenuous domestic work by 4 percentage points. On average, house work is more strenuous than the kind of market work that women were doing in the labour market, so this led to an overall reduction in the strenuousness of life.”

“Men have reduced the time they spend at market work over the last 30 years. While they increased the time they spend doing housework by a small amount, they switched from strenuous housework activities like maintenance and DIY to less strenuous ones like child care and shopping.”

Children, likewise, can be seen to have substituted a lot of physical activity for sedentary ones, with the rise of smart phones and electronic games.

What implications does this research have for policy? They conclude that it does not mean that we should abandon policies that target food spending or calories, such as the recent introduction of a tax on sugary drinks.

But we should note that leisure time activity may be unlikely to contribute sufficient energy expenditure to prevent increases in the prevalence of overweight and obesity, as it is actually of short duration compared to the day at work.

This is because are eating too much given their low (and declining) level of physical activity at work and at home.

Looking at work and the systemic changes which have taken place in the workplace must form part of any holistic strategy, but as yet the studies are relatively new of how our bodies have adapated to a world in which work is actually too easy - from a physical point of view.

They conclude their study by saying:

“It does mean that physical activity and calories are linked in potentially complex ways, and it is important to better understand this and the implications it has on people's behaviour in order to inform policy.”


1 comment:

Nick Palmer said...

Often overlooked is the large contribution to weight gain from modern levels of heating both, at home and at work. A very significant part of our calorie input is used to keep our body temperatures warm.