An overweight mother quickens a child's path to obesity, according to a new study.

Other factors included too much time spent in front of the TV and rapidly piling on the pounds in early childhood.

The researchers, from Auckland University, base their findings on 571 New Zealand children of European heritage, who were regularly monitored from birth to the age of 7 years.

Their percentage body fat, a reliable indicator of overweight and obesity, was calculated at the age of 3½ and 7 years.

TV viewing time and the amount of physical activity they took part in were also measured at the age of 7.

Children who had acquired a high percentage body fat by the age of 3½ were significantly more likely to be obese at the age of 7 than those with low percentage body fat.

Children who had rapid growth spurts were more at risk.

But having a mother who was overweight or obese, being a girl, and spending a lot of time in front of the TV were all independently associated with the chances of becoming obese.

Children with overweight or obese mothers had around 4 per cent more body fat than those whose mothers were of normal weight.

It is not clear if genes, exposure to specific factors during pregnancy, or shared lifestyle factors are to blame, according to the researchers.

Children who spent more than 3 hours a day in front of the TV had 5 per cent more body fat than those who watched TV for less than an hour.

Unsurprisingly, doing very little exercise also significantly boosted the chances of obesity. Every additional hour of inactivity added almost 1 per cent of body fat.

The study is published ahead of print in the Archives of Disease in Childhood.