Sydney, Aug 3 - Female twins who are small at birth have a greater likelihood of being obese as adults, according to a new study.

Scientists in Britain and Otago University (OU) in Australia found that twin girls with a lower birth weight were found in later life to have higher amounts of fat compared to lean body tissue than the twins who were heavier at birth. They conducted a study of 3,170 female twins aged 18 to 80 in Britain.

Conversely, those who were heavier at birth had a higher ratio of lean body mass to fat mass once in adulthood.

'A girl who is a twin, with a birth weight of 2.5 kg, will have around 500 grams less fat in adulthood than a twin girl with a smaller birth weight of 1.5 kg,' said Paula Skidmore, nutritionist at OU.

The average weight at birth for a twin girl is 2.5 kg. All the twins had their adult weight and total fat measured using dual-energy X-ray absorptiometry, and were asked to recall their birth weights for the purposes of the study.