Researchers have discovered another downside of bitterly cold weather in winter - it leads to babies who become fat in later life.

A team from Southampton University has found that babies born in cold winters are more likely to suffer from obesity as adults.

The research is the first time that a link has been established between climate at birth and adult obesity.

The Southampton team joined forces with Chicago's Northwestern University Medical School to examine 1,750 men and women born in Hertfordshire between 1920 and 1930.

They found there was a marked increase in the body mass index among men born in cold winters throughout the decade.

The effect was also apparent for the women, although less pronounced.

Body mass index is a measure of obesity based on a person's height and weight. The higher the figure, the more obese the person.

Lead researcher Professor David Phillips said: "This is the first indication that a link exists between climate at birth and adult obesity, but we don't properly understand why it occurs.

"It could, however, be particularly important for poorer families who can't afford to heat their houses adequately.

"It's the relative change in temperature that seems to be more important, which might explain why the children of people who emigrate from hot to colder climates are prone to put on weight.

"In evolutionary terms, it's sensible to be fatter if you are born in a colder climate for insulation.

"We know that people are fatter in Scotland than in England, and climate may go some way towards explaining that."

Dr Andrew Hill, of Leeds University and chairman of the Association for the Study of Obesity, said the research was "interesting".

But he said: "To suggest that the body responds to changes in the external environment by setting up something that happens 30-40 years later is a bit of a leap of faith.