A single gene may fuel the tendency to overeat
Scientists have produced more evidence that carrying the wrong variant of a single gene can raise the risk of overeating and obesity.
Several studies have suggested that carrying one of two variants of the FTO gene make overeating more likely.
A University College London team found children carrying one or two of these variants were more likely to binge on biscuits after eating a meal.
The study appears in the International Journal of Obesity.
The researchers hope their work will shed more light on why some children become overweight or obese.
They believe a greater understanding of the impact of specific genes paves the way for new therapies to minimise their effect.
It is thought that more than half the European population carries at least one of the two key FTO variants.
A previous study found children who carry one specific variant of the FTO gene eat an average of 100 extra calories per meal.
They were more likely to eat food loaded with sugar and fat, rather than more healthy options.
However, a separate study found vigorous physical activity could blunt the effects of carrying the key FTO variants.
In the latest study, the UCL team offered 131 four to five-year-olds a mixed plate of sweet and savoury biscuits within one hour of finishing a full meal.
Those who carried one or two of the key FTO variants were more likely to tuck in despite the fact that they should have been full.
Lead researcher Professor Jane Wardle said: "We believe this research tells us more about how some children are more responsive to signals in their bodies encouraging them to eat when full than others.
"Knowing how the genes work is the first step to minimising these negative effects.
"The occasional treat won't do us any harm - but this study showed that some children don't know when to stop - which could lead to the onset of obesity and a lifetime of health problems.
"Children with higher risk versions of the gene might be helped if parents do their bit to keep temptations out of the home."
Obesity is linked to a range of health problems, including heart disease, diabetes, and a raised risk of a wide range of types of cancer.
It is estimated that a quarter of all cancer deaths are caused by unhealthy diets and obesity.
But in the UK alone, it is estimated that 12,000 people every year could avoid cancer by maintaining a healthy body weight.
Sara Hiom, of the charity Cancer Research UK said: "It's important to remember that not all children with these 'high' risk genes will over eat - other influences are very important too - including the eating habits of parents and the types of food made available."
Ms Hiom urged parents to provide healthy snack options such as carrot sticks rather than chocolate biscuits and ideally to encourage children to stop eating when full.
Dr Ian Campbell, medical director of the charity Weight Concern, said: "The danger is we might be tempted to think that one day there may be a test to identify at-risk children. This is unlikely.
"The real importance of this research is a greater understanding of the forces that drive obesity.
"But everyone caring for a child has to be alert to the risks of an excessive diet and inactive lifestyle and help, encourage their child towards a healthy lifestyle, preferably leading by example."