More than 6,000 genes help to determine an individual's body weight, new research suggests.
A study appearing in the journal BMC Genetics surveyed the Jackson Mouse Genome Database to determine the body weights of various 'knockout mouse' strains.
Knockout mice are animals that have had a specific gene inactivated, enabling researchers to observe how they differ from normal mice and thereby determine the role of that particular gene.
The analysis enabled researchers from the Monell Centre to calculate that over 6,000 genes - about 25 per cent of the entire genome - may contribute to a mouse's weight.
The findings are relevant to the impact of human genes on body weight, as mice and humans share many of the same genes.
Commenting on the findings, behavioural geneticist Dr Michael Tordoff commented: "It is interesting that there are ten times more genes that increase body weight than decrease it, which might help explain why it is easier to gain weight than lose it."
The expert added that each newly discovered 'obesity gene' that is documented in the press "is just one of the many thousands that influence body weight", making a quick solution to the obesity problem "unlikely".