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Energy and Equity
- Gregory Rose (18 June 2007)
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Gregory Rose, Head of Health Intelligence North Staffordshire Primary Care Trust, Leek, Staffordshire ST13 6HQ
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Dear Editor The key points accompanying the Samdal et al (1) paper on physical activity and television viewing, state that “it does not appear increasing obesity in European adolescents is explained by decreasing physical activity or increasing TV viewing”. The study did not measure all physical activity, only self-reported vigorous physical activity (that which results in breathlessness and sweating). This does not reflect physical activity in general, nor total energy expenditure. The assumption is that these periods of vigorous physical activity account for the majority of physical activity in the day, and we know that they do not. People spend more time doing simple walking or moderate physical activity: while only 20.6% of adults in the West Midlands, England, engaged in a mere 20 min of vigorous physical activity on at least 5 days, 41.1% engaged in moderate activity for at least 30 min. (2) The authors admit in their discussion that their data do not adequately reflect total physical activity yet their key points assert that changing physical activity is probably not related to increased population obesity. Furthermore, television watching is not indicative of all, or even the majority of, sedentary activity in teenagers in environments of rapid technological change – specifically from the late-1980s to the present in Europe. (3) Again, this was acknowledged but no attempt was made to interpret replacement by other entertainment choices. Clearly, if television watching is “little changed” and computer/game use is increasing, time spent engaged in sedentary activities is probably increasing, whether in the same groups that also watch TV or others. We know that computer use after school has greatly increased in England. (4) In some ways the comparison of television watching with physical activity is an anachronism. In making their claim the authors could have described the time period in which this increase in obesity has occurred, and by how much, and in which countries. The data as presented are useful for testing an association between population vigorous physical activity and television watching, but not to make judgments about the cause of an unspecified increase in obesity during an undefined period. Behavioural and dietary changes over time are difficult to measure as the scope of behaviours cannot always be predicted at baseline. Unfortunately they cannot be made prospectively to justify retrospective trends, so we must rely on what data have already been gathered. The combined evidence from the Health, (5) Food (6) and Travel (7) Surveys of adults in England/Great Britain indicates that energy consumption is not the main factor in increasing population overweight in that population. In fact household energy intake has decreased and even energy consumed as “eating out” cannot remotely account for the trend as it is also shown to reduce slightly. Reduced energy expenditure has occurred, though, in both children and adults. This is as measured by proxies which have a greater role in daily life than television watching (which often merely replaces sitting or evening dining at a table) i.e. replacement of walking or cycling by driving. From our local evidence, for adults in their 50s obesity is a three- fold greater problem than teen obesity (using the International Obesity Task Force cut-offs (8) which are comparable with a BMI of 30 in adults). Even with this and the above evidence, the majority of health professionals and media commentators continue to dwell on teens and diet, citing selectively, with the seemingly commonsensical statement that fatness is driven what goes in the mouth, and that alone. Consumption is an important part but it threatens to overshadow changing behaviours which are shaping our societies and environments, and which began in the middle of the last century: the way we move within our environments. (9) An unbalanced focus helps to ensure that solutions, politically sensitive because they will certainly be unpopular, are even less likely to be sought. References 1 Samdal, O, Tynjälä J, Roberts C, Sallis JF, Villberg J, Wold B. Trends in vigorous physical activity and TV watching of adolescents from 1986 to 2002 in seven European Countries. Eur J Public Health Vol. 17, No. 3, 242–248. 2 West Midlands Regional Lifestyle Survey © 2005, WMRO and WMPHO. [Weighting frame included age, sex, ethnicity, deprivation] 3 Reimer J. Total share: 30 years of personal computer market share figures: The rise of the PC (1987-1990). 2005. epub. http://arstechnica.com/articles/culture/total-share.ars/6 [accessed 05/06/2007] 4 SHEU [An occasional newsletter from SHEU] Schools Health Education Unit. October 2004: 2 5 Department of Health. Health Surveys for England. 6 MAFF/Defra. National Food Surveys. Great Britain. 7 Department for Environment Transport and Regions. National Travel Surveys Great Britain. 8 Cole TJ, Bellizzi MC, Flegal KM, Dietz WH. Establishing a standard definition for child overweight and obesity worldwide: international survey. BMJ 2000. 320(7244):1240-3. 9 Illich, I. Energy and Equity. London: Calder & Boyars; 1974. Conflict of Interest:None declared |
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