Three year old children who spend more than eight hours watching television per week are at an increased risk of obesity, reveals a new study by researchers at the Universities of Glasgow and Bristol in the British Medical Journal this week.

This is just one of eight aspects of early life found to be linked to obesity in UK children, and these results support the theory that the early life environment can determine later risk of obesity.

The study was led by Dr John Reilly, Reader in Paediatric Energy Metabolism at the University of Glasgow. He explains:

"Most of the UK's current public health strategies are concerned with the growing scale of obesity and helping adolescents or adults who already have a problem. This paper suggests that people begin on a path to later obesity as a result of exposure to risk factors early in life. Even events in the womb can be important. As a society, if we want to prevent obesity successfully we need to find new ways of modifying the extent to which babies and young children are exposed to these risk factors."

"Future strategies may focus on environmental changes and attempting to modify factors during pregnancy, in infancy, or in early childhood, which are independently related to later risk of obesity.'

The study involved 8,234 children aged 7 years and a further sample of 909 children who were taking part in a large UK study of parents and children. Height and weight were measured and body mass index (BMI) was calculated.

In the entire group, four factors were independently associated with a risk of obesity at age 7:

* Increasing birth weight

* Parental obesity (one or both parents)

* More than eight hours spent watching television per week at age 3years

* Short sleep duration (less than 10.5 hours per night at age 3 years

A further four factors were significant for the children in the additional sample:

* Size in early life

* Rapid weight gain in the first year

* Rapid catch-up growth between birth and two years

* Early development of body fatness in the pre-school years, before the age at which body fat should be increasing (at age 5/6 years)

The precise mechanisms by which these variables might increase the risk of obesity are complex, say the authors. For instance, parental obesity may increase the risk of obesity through genetics, or by shared family characteristics in the environment such as food preferences.

Duration of night time sleep may affect growth hormone secretion or reduce the child's exposure to food intake in the evening. Alternatively, children who are more physically active may sleep longer at night. Finally, television viewing may confer risk through a reduction in energy expenditure or an increase in dietary intake.

Full details of the paper can be found at: BMJ webpage.

Media Relations Office (media@gla.ac.uk)

For more details please contact John Reilly on 0141 201-0712. Alternatively contact the University Press Officer on 0141 330-3535.

First published: 19 May 2005