Is the environment making you fat?

A great report on a new book by Cathy Banwell, Megan Shipley and Lyndall Strazdins "The 7 Deadly Sins of Obesity: How the Modern World is Making us Fat" University of (NSW Press, 2007). Beyond the oversimplification of the 'energy in is greater than the energy out' argument, some thought provoking research into environmental issues that are creating obese nations.

There's more to obesity than eating

Reality television shows built around people losing weight are fuelling an oversimplified view of what makes people fat, writes Christopher Scanlon

28apr07

WHICH of the following is the most effective weight loss tool used on reality TV show The Biggest Loser – the gruelling daily workouts; the improved diet; or the "White House", the North Shore Sydney mansion where the show is filmed?

It's a trick question.
All these factors play an important role in the impressive weight loss contestants experience over the course of the show. If you've ever battled with a weight problem, though, you'd choose the White House hands down.

Why? Because the exercise regimes and the dietary changes are a product of the artificial environment created in the house and its grounds. Such radical changes in body size would be almost unthinkable if, instead of being holed up in a mansion, the contestants were left to their own devices.

The Biggest Loser house powerfully illustrates a frequently overlooked factor in the national debate about obesity: our environment is making us fat.

As Australian health researchers Cathy Banwell, Megan Shipley and Lyndall Strazdins write in their book The 7 Deadly Sins of Obesity: How the Modern World is Making us Fat, published by University of NSW Press (2007), parents "and their children are caught in an obesogenic environment that is itself the product of cultural, social and economic trends, many of which are promulgated by the marketplace and government".

Policy-makers are loath to acknowledge the effects of the environment, preferring instead to attack the food industry, or to see obesity as a matter of individual willpower and lifestyle.

The federal Government's program for tackling obesity, Building a Healthy, Active Australia, reflects the individual-willpower approach. The four-year program encourages people to exercise more and eat a healthier diet. Federal Health Minister Tony Abbott – a veteran runner and general exercise fanatic – sums up the underlying philosophy of the program in his view that the weight game is "a simple equation: energy in minus energy out equals weight gain or loss".

The Minister is right of course – up to a point. Blaming society because your jeans no longer fit is easier than admitting that Silverchair were still at high school when you last went for a run.

But when you start to think through the "energy out" side of the equation, that all starts to look a bit too simple. Energy expenditure is dependent on the environment that is shaped by culture, social and economic factors, the interplay of which turns out to be quite complex.

A study in the International Journal of Obesity, published last November, illustrates this point. The authors of the study questioned the main two reasons given for rising obesity rates in the US, namely reduced physical activity and the manufacturing process and marketing of high-calorie foods.

While activity levels and food manufacturing and marketing practices are certainly important factors in the obesity epidemic, the authors of the study claim that they are far from the whole story.

The authors nominated 10 other candidates linked to rising obesity rates. Some of the nominations were surprising.

Sleeping less, for example, has been shown to lead to increased hunger and appetite. The authors noted that over the past several decades, sleep has reduced from an average of nine hours per night to just over seven hours.

Airconditioning and ducted heating are also straining our waistbands. The reason? If you have the airconditioning roaring or the central heating humming, then you're burning less energy to regulate your body's temperature. The authors estimate that between 1970 and 2000 the average temperature in homes in the UK rose from 13C to 18C, and that between 1923 and 1986, the standard temperature in US homes in winter rose from 18C to 24.6C.

The result is that our bodies have had to burn less energy to maintain a comfortable temperature.

Broader lifestyle and demographic changes are also believed to be linked. For example, the age at which a woman gives birth has been linked to child obesity. One study of nine to 10-year-old girls found "that the odds of obesity increased 14.4 per cent for every five-year increment in maternal age".

Changing patterns of drug use have also been implicated in the obesity epidemic.

One of the unintended side effects of public health campaigns and legislation to reduce smoking, for example, has been increasing obesity. Nicotine is a well-known appetite suppressant and increases the metabolism. On average, smokers weigh less than non-smokers – though that's hardly an endorsement of Kath and Kim's nicotine-driven approach to weight loss.

At the same time as smoking rates have gone through the floor, prescriptions of some anti-psychotic medications, anti-diabetic drugs and contraceptives linked to weight gain have increased.

Australia is a particularly striking example of such changes. According to the OECD the number of daily smokers among adults dropped from 35.4 per cent in 1983 to 17.7 per cent in 2004.

Meanwhile, between 1990 and 2004 there has been a twofold increase in the use of insulin to treat diabetes. Insulin is often associated with weight gain.

The study's authors caution that none of these factors is definitively related to rising obesity rates. Their point, rather, is that taken together they are plausible candidates for rising obesity levels.

In separate recent research, evidence has been found that some people's genes may make them more prone to become overweight; and another study even found "strong evidence . . . that associates certain viruses with obesity".

Obesity researchers in Australia have backed the findings of the IJO review, although with some local variations. Cathy Banwell from the National Centre for Epidemiology and Population Health at the ANU, for example, says that she would expect the background of immigrants to vary the effects of demographic changes on obesity levels.

A higher proportion of Asian migrants, as compared with Hispanic immigrants looked at in the US study, is 'unlikely to contribute to a population-level increase in weight, even though they too have put on weight', suggests Banwell.

The study in the International Journal of Obesity claims that ignoring other factors in rising obesity may lead to "well-intentioned but ill-founded proposals for reducing obesity rates".

Kylie Ball, a senior research fellow with Deakin University's School of Exercise and Nutrition Sciences, says strategies to combat obesity that fail to take account of societal and environmental factors on behaviour are unlikely to succeed in the long-term.

"Unfortunately, I think the approach taken to date has failed from this point of view," says Ball. "Our federal Health Minister has explicitly stated his position on obesity – individuals are solely responsible for the food choices and physical activity decision they make. This is reflected in obesity strategies which have tended to place the focus for weight loss/management on individuals themselves. This is problematic when we consider that individual choices are often constrained by factors within the social, physical, economic and policy environment."

Ball advocates a range of prevention measures to complement individually targeted initiatives. These include infrastructure and incentives to encourage active transport, such as greater use of bicycles, and childcare to help overcome pressures associated with lack of time and work/family commitments.

"We need a better understanding of the impact of these environmental factors on obesity risk, as well as a more detailed evidence base to underpin prevention efforts', she says.