Published in the December issue of the American Journal of Preventive Medicine, the new study adds further clout to the well-documented observation that excessive television viewing harms kids' health both by encouraging sedentary activity and promoting the consumption of junk foods.
Although difficult to interpret, the emergence of more and more studies linking TV and obesity is placing increasing pressure on the food industry, which is embroiled in the battle to limit junk food advertisements and the promotion of food of minimal nutritional value to children.
Obesity, which is known to increase the possibility of cardiovascular risk factors, such as hypertension, is though to affect 17 percent of children and adolescents in the US, while 30 percent of European children are considered overweight.
According to the findings of this latest study, children watching two to four hours of TV had 2.5 times the odds of hypertension compared with children watching zero to two hours. The odds of hypertension for children watching four or more hours of TV were 3.3 times greater than for children watching zero to two hours.
The study was based on an investigation of 546 children and adolescents aged four to 17. They were evaluated for obesity at pediatric subspecialty weight management clinics in San Diego CA, San Francisco CA, and Dayton, OH, from 2003 to 2005.
The researchers gathered information on TV viewing times through questionnaires and interviews. The height and weight of the children were measured to determine a Body Mass Index (BMI) and their blood pressures were recorded.
After controlling for race, site, and BMI score, researchers determined that both the severity of obesity and daily TV time were significant independent predictors of the presence of hypertension.
Another study conducted last year by researchers from the Harvard School of Public Health and Children's Hospital Boston found that each hour increase in television viewing by children resulted in the consumption of an additional 167 calories.
Indeed, television viewing by children has been in the spotlight in recent years with regard to the obesity debate. Food manufacturers are being encouraged - or even cautioned - to implement voluntary advertising restrictions in the US in order to offset the threat of new regulations.
Last year, the Council of Better Business Bureau's (CBBB) Children's Food and Beverage Advertising Initiative was set up as a voluntary self-regulation program for industry. Participants adopted nutrition standards for all marketing aimed at children, and also committed to devote at least half of their kids' advertising to promote healthier products, good nutrition and healthy lifestyles.
This is now made up of 13 participants: Cadbury Schweppes, Campbell Soup, Coca-Cola, General Mills, Hershey, Kellogg, Kraft, McDonald's, PepsiCo, Unilever, Masterfoods, Burger King, and ConAgra.
The UK has gone one step further by implementing new regulations. The nation's advertising watchdog, the Office of Communications (Ofcom), last year said that it would impose a total ban on high in fat, salt and sugar (HFSS) food and drink advertisements of particular appeal to children under the age of 16, broadcast at any time of day or night on any channel.
The announcement of the new restrictions on food and soft drink advertising to children on TV was the culmination of a three-year debate on the role advertising plays in establishing eating habits.
Under Ofcom's proposals, restrictions will be targeted at food and drink products rated as HFSS according to the Nutrient Profiling scheme developed by the Food Standards Agency (FSA). Food or drink products which are below FSA thresholds may be advertised without scheduling restrictions, providing an incentive for some manufacturers to reformulate existing products as well as to develop new products which are low in fat, salt and sugar.