The EarlyBird study by researchers from the Peninsula Medical School in Plymouth, followed the development of over 200 children in Plymouth born in 1995 and 1996 and found that when these children were aged between five and eight, 42% of boys and only 11% of girls met the government recommended daily exercise level of one hour of moderate exercise.

The study also found that exercise alone had no positive effect on weight control over time but when compared with peers who took less exercise, children who met the recommended activity levels fared better for blood pressure, cholesterol, triglycerides and insulin resistance, which is a recognised precursor to type 2 diabetes later in life.

The researchers say this does not mean that exercise has no health benefits for children but improving children's diets, is likely to have a greater impact on their overall health and weight.

The researchers worked with 212 children from 54 schools in Plymouth and followed them for four years - once each year the children were tested by wearing small monitors that recorded their exercise levels - and the amount of physical activity achieved by children each day varied considerably - some only managed 10 minutes of moderate exercise, while others went over 90 minutes.

Dr. Brad Metcalf who led the study says the results for girls are in line with past research that shows that young girls do not exercise as much as boys but some children are more naturally active than others and this might explain why there is such a marked difference between boys and girls.

Dr. Metcalf says at present it is unclear whether exercise guidelines should be adjusted for this difference, or whether girls should be encouraged to exercise more.

The Australian National Preventative Health Task force in a preliminary report says in the 15 years, from 1990 to 2005, the number of overweight Australian adults soared by a staggering 2.8 million and currently, almost one quarter of children are overweight or obese.

The report says recent trends in Australian children predict that their life expectancy will fall two years by the time they are 20 years old, back to the levels seen for males in 2001 and for females in 1997 and is not a legacy we should be leaving our children'.

Experts say it is possible for children to suffer from type two diabetes a disease more usually found in older people which is associated with obesity, lack of exercise and poor diet.

They say if obesity rates continue to grow there is a danger it will become the leading disease for men and the second most common disease for women in 15 years time and will have huge ramifications for public health costs.

Proposals by the task force to stem obesity include improving access to healthier foods and ensuring that healthy eating and exercise are part of everyday life in schools, workplaces and communities, along with a crackdown on junk food marketing to children.

The task force also suggests an overhaul is called for of town planning to encourage walking, cycling and sport.

The British research is published in the current issue of the journal "Archives of Diseases in Childhood."