Is it any wonder kids are fat?

While the debate over childhood obesity rumbles on and experts search for reasons for the epidemic, a clutch of new studies recently published suggests the causes are a combination of factors.

Foremost though appears to be the immediate environment children find themselves in.

Much of the blame is attributed to media advertising where children are bombarded at school and at home by adverts for drinks, junk food and fast food..... where often rewards are offered in the form of toys or games.

The decline too of many sports and physical activities in schools also plays a significant part in the childhood obesity epidemic as does the rise in sedentary activities such as computer games.

Experts suggest the combination of such factors may explain why childhood obesity has reached such proportions and they say environmental factors and policies are challenging the health of children in America.

A number of new studies by researchers at the University of Illinois-Chicago and the University of Michigan examined teenagers' surroundings, and their findings confirm earlier research.

Their conclusions appear in a special supplement of the American Journal of Preventive Medicine and say schools and communities will continue to encourage the childhood obesity epidemic until policies are adopted to improve the health of children and communities.

They believe policy changes could make healthy choices easier.

Lisa Powell of the University of Illinois, Chicago, examined restaurant and food store options in neighborhoods and food-related television advertising aimed at teens.

She says lower-income neighborhoods tend to have a higher proportion of fast-food restaurants, and black urban neighborhoods have the highest percentage of fast-food restaurants.

Powell says when people rely on convenience stores that seem to proliferate in many poor neighborhoods, families eat less healthy food.

Powell and her colleagues studied more than 200,000 adverts on top-rated shows viewed by teens aged 12 to 17 in 2003 and 2004 and found more than a quarter were for fast food, sweets and beverages, all items well within a teenager's budget.

Overall, fast-food advertising comprised 23 percent of all food-related ads seen by teens.

According to a study by Lloyd Johnston and colleagues at the University of Michigan, teens have ready access to high-fat, sugary foods and drinks at school and the majority of middle schools and high schools had contracts with a soft-drink company.

The researchers recommend that supermarkets be placed in 'food deserts' in inner cities so people have access to healthy food; food companies stop marketing unhealthy foods to children; schools create more opportunities for physical activity and limit offerings of unhealthy foods and beverages.

Meanwhile, parents can make a difference, says social psychologist Lloyd Johnston of the University of Michigan and parents must act by being good role models for their children.

The research was financed by the Robert Wood Johnson Foundation and is published in the American Journal of Preventive Medicine.