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Warning: too much TV is a health hazard |
Encouraging patients to exercise regularly is now truly on the GP agenda with plenty of evidence to back up the rationale for this. But how do we feel about telling our patients to be less sedentary, particularly questioning them as to how many hours of TV they watch and in many cases telling them to watch less? Compelling data suggests that this is just what we should be doing.
Recent data published in the AMJ(1) from the AusDiab study has shown some alarming rates of overweight and obesity. In 1980, 7.1% of the population aged 25-64 years living in major cities in Australia were obese. Using the same age and geographical restrictions, the prevalence (defined by BMI) in the study was found to be 18.4% showing a 2.5-fold rise over 20 years. The sequelae of this epidemic are now obvious, as exemplified by Australia having one of the highest rates of type 2 diabetes in the developed world.(2)
The Australian study also found that physical activity time and TV viewing time were the strongest correlates with obesity. It was concluded that reducing time spent on sedentary TV watching needed further research in prospective studies but it is likely to be found to be an important strategy for addressing the obesity epidemic.
A recent US prospective study(3) conducted from 1992-1998 in the Nurses Health Study looking at more than 50,000 women found that independent of exercise levels, sedentary behaviours, especially TV watching, were associated with significantly elevated risk of obesity and type 2 diabetes, whereas even light to moderate activities were associated with substantially lower risk. Moderate intensity activity such as brisk walking was found to be strongly protective against type 2 diabetes.
So why is TV viewing so obesogenic? There are three potential mechanisms. Firstly TV watching displaces physical activity and thereby reduces energy expenditure. Secondly people tend to eat whilst watching TV. Thirdly people who spend more time watching TV tend to follow an unhealthy eating pattern that may be influenced by TV advertising.
A junk food advertising audit conducted by the Australian Divisions of General Practice National Divisions Youth Alliance in January 2003 analysed 50 hours of child targeted TV on commercial stations. The audit found that during children’s TV programs there was an average of one junk food (ie. food high in fat, sugar and/or salt with little nutritional value) advertisement per ad break and in some cases three per ad break. The main categories of food advertised were fast food (hamburgers, pizza and fried chicken), soft drink, chocolate confectionery and ice cream. Children watching two and a half hours of TV a day during the holiday period would have been exposed to 406 advertising messages encouraging them to eat junk food.
Australia currently does not allow ads during programming for preschoolers. How does this compare with other countries? In the US there are currently few restrictions or standards for food advertising and marketing aimed at children. Strong policies exist, however, in other countries. Denmark, Norway, Sweden, and Finland do not permit commercial sponsorship of children’s programs.(4) Sweden and Norway do not permit any television advertising to be specifically directed to children under 12 and no advertisements are allowed during children’s programming.
Australia clearly needs to seriously consider the Scandinavian approach in the interests of an effective strategy to control the obesity epidemic. The food industry lobby’s aim to sell the ‘eat more’ message must be resisted. In the meantime telling our patients to reduce sedentary behaviour, particularly TV watching, will complement the advice encouraging higher levels of physically activity.
(1) Cameron, A et al. Overweight and obesity in Australia: the 1999-2000 Australian Diabetes, Obesity and Lifestyle Study (AusDiab) MJA 2003; 178 (9): 427-432
(2) Dunstan DW, Zimmet PZ, Wellborn TA et al. The rising prevalence of diabetes and impaired glucose tolerance: the Australian Diabetes, Obesity and Lifestyle Study. Diabetes Care 2002; 25: 829-834
(3) Hu, F et al. Television Watching and Other Sedentary Behaviours in Relation to Risk of Obesity and Type 2 Diabetes Mellitus in Women. JAMA 2003 Vol 289, No 14 1785-1791
(4) Consumers International. A spoonful of sugar: television food advertising aimed at children: an international comparative survey. Available at: http://www.consumersinternational.org/campaigns/tvads/index.html. Accessed May 22, 2002.
Editor's note: Andrew Binns is currently attending the 12th European Congress on Obesity in Helsinki and a satellite symposium on Physical Activity and Weight Management in Tampere, Finland and will continue to update GPSpeak readers on the latest research in obesity and physical activity relevant to GPs.
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